bdh2 encodes a cytosolic short-chain dehydrogenase/reductase implicated in mammalian/eukaryotic siderophore biogenesis, mitochondrial iron delivery, heme synthesis, and erythroid maturation in zebrafish. The core review distinguishes the specific 4-oxoproline reductase detoxification activity from the separate 2,5-DHBA-associated siderophore/heme role, while 3-hydroxybutyrate dehydrogenase activity is treated as a possible secondary/by-similarity activity rather than the main zebrafish functional theme.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0003858
3-hydroxybutyrate dehydrogenase activity
|
IBA
GO_REF:0000033 |
KEEP AS NON CORE |
Summary: 3-hydroxybutyrate dehydrogenase activity (GO:0003858) is supported or plausible for zebrafish bdh2, but it is not the most informative core function. Falcon deep research reinforces keeping this non-core, noting BDH2 is only ~20% identical to mitochondrial BDH1 and is considered dispensable for bulk ketone-body metabolism in vivo, with its conserved role being siderophore-dependent iron handling rather than ketone oxidation.
Reason: 3-hydroxybutyrate dehydrogenase activity is described as a possible/by-similarity activity and is not the main zebrafish siderophore/heme function.
Supporting Evidence:
file:DANRE/bdh2/bdh2-uniprot.txt
hydroxybutyrate dehydrogenase (By similarity).
file:DANRE/bdh2/bdh2-deep-research-falcon.md
is described as only ~20% identical to mitochondrial BDH1 and is considered dispensable for ketone-body metabolism in vivo in the mouse knockout study
|
|
GO:0005737
cytoplasm
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: cytoplasm (GO:0005737) is supported for zebrafish bdh2 and is coherent with the synthesized gene function.
Reason: The cytoplasmic location is supported.
Supporting Evidence:
file:DANRE/bdh2/bdh2-uniprot.txt
SUBCELLULAR LOCATION: Cytoplasm
|
|
GO:0019290
siderophore biosynthetic process
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: siderophore biosynthetic process (GO:0019290) is supported for zebrafish bdh2 and is coherent with the synthesized gene function. Falcon deep research reinforces this as the central conserved role, identifying Bdh2 as the rate-limiting NAD-dependent enzyme of 2,5-DHBA (endogenous catecholate siderophore) biosynthesis and a functional homolog of bacterial EntA.
Reason: Siderophore biosynthesis is a central supported role of Bdh2/BDH2.
Supporting Evidence:
file:DANRE/bdh2/bdh2-uniprot.txt
formation of 2,5-dihydroxybenzoate (2,5-DHBA)
PMID:20550936
The iron-binding moiety of the mammalian siderophore is 2,5-DHBA
file:DANRE/bdh2/bdh2-deep-research-falcon.md
BDH2 catalyzes a **rate-limiting NAD-dependent step** in biosynthesis of **2,5-dihydroxybenzoic acid (2,5-DHBA)**, an endogenous catecholate that can coordinate iron
file:DANRE/bdh2/bdh2-deep-research-falcon.md
BDH2 is a functional homolog of **bacterial EntA**, linking its enzymology to catecholate siderophore chemistry
|
|
GO:0003858
3-hydroxybutyrate dehydrogenase activity
|
IEA
GO_REF:0000120 |
KEEP AS NON CORE |
Summary: 3-hydroxybutyrate dehydrogenase activity (GO:0003858) is supported or plausible for zebrafish bdh2, but it is not the most informative core function. Falcon deep research reinforces keeping this non-core, noting BDH2 is only ~20% identical to mitochondrial BDH1 and is considered dispensable for bulk ketone-body metabolism in vivo, with its conserved role being siderophore-dependent iron handling rather than ketone oxidation.
Reason: 3-hydroxybutyrate dehydrogenase activity is described as a possible/by-similarity activity and is not the main zebrafish siderophore/heme function.
Supporting Evidence:
file:DANRE/bdh2/bdh2-uniprot.txt
hydroxybutyrate dehydrogenase (By similarity).
file:DANRE/bdh2/bdh2-deep-research-falcon.md
is described as only ~20% identical to mitochondrial BDH1 and is considered dispensable for ketone-body metabolism in vivo in the mouse knockout study
|
|
GO:0005737
cytoplasm
|
IEA
GO_REF:0000044 |
ACCEPT |
Summary: cytoplasm (GO:0005737) is supported for zebrafish bdh2 and is coherent with the synthesized gene function.
Reason: The cytoplasmic location is supported.
Supporting Evidence:
file:DANRE/bdh2/bdh2-uniprot.txt
SUBCELLULAR LOCATION: Cytoplasm
|
|
GO:0016617
4-oxoproline reductase activity
|
IEA
GO_REF:0000120 |
ACCEPT |
Summary: 4-oxoproline reductase activity (GO:0016617) is supported for zebrafish bdh2 and is coherent with the synthesized gene function.
Reason: 4-oxoproline reductase activity is the specific UniProt catalytic activity for this SDR enzyme.
Supporting Evidence:
file:DANRE/bdh2/bdh2-uniprot.txt
conversion of 4-oxo-L-proline to cis-4-hydroxy-L-proline
|
|
GO:0003858
3-hydroxybutyrate dehydrogenase activity
|
ISS
GO_REF:0000024 |
KEEP AS NON CORE |
Summary: 3-hydroxybutyrate dehydrogenase activity (GO:0003858) is supported or plausible for zebrafish bdh2, but it is not the most informative core function. Falcon deep research reinforces keeping this non-core, noting BDH2 is only ~20% identical to mitochondrial BDH1 and is considered dispensable for bulk ketone-body metabolism in vivo, with its conserved role being siderophore-dependent iron handling rather than ketone oxidation.
Reason: 3-hydroxybutyrate dehydrogenase activity is described as a possible/by-similarity activity and is not the main zebrafish siderophore/heme function.
Supporting Evidence:
file:DANRE/bdh2/bdh2-uniprot.txt
hydroxybutyrate dehydrogenase (By similarity).
file:DANRE/bdh2/bdh2-deep-research-falcon.md
is described as only ~20% identical to mitochondrial BDH1 and is considered dispensable for ketone-body metabolism in vivo in the mouse knockout study
|
|
GO:0005737
cytoplasm
|
ISS
GO_REF:0000024 |
ACCEPT |
Summary: cytoplasm (GO:0005737) is supported for zebrafish bdh2 and is coherent with the synthesized gene function.
Reason: The cytoplasmic location is supported.
Supporting Evidence:
file:DANRE/bdh2/bdh2-uniprot.txt
SUBCELLULAR LOCATION: Cytoplasm
|
|
GO:0016617
4-oxoproline reductase activity
|
ISS
GO_REF:0000024 |
ACCEPT |
Summary: 4-oxoproline reductase activity (GO:0016617) is supported for zebrafish bdh2 and is coherent with the synthesized gene function.
Reason: 4-oxoproline reductase activity is the specific UniProt catalytic activity for this SDR enzyme.
Supporting Evidence:
file:DANRE/bdh2/bdh2-uniprot.txt
conversion of 4-oxo-L-proline to cis-4-hydroxy-L-proline
|
|
GO:0042541
hemoglobin biosynthetic process
|
IMP
PMID:26929344 Inactivation of 3-hydroxybutyrate dehydrogenase 2 delays zeb... |
KEEP AS NON CORE |
Summary: hemoglobin biosynthetic process (GO:0042541) is supported or plausible for zebrafish bdh2, but it is not the most informative core function. Falcon deep research clarifies that the hypochromic/hemoglobinization phenotype reflects impaired heme/iron handling rather than globin transcription, since hbae1/hbae3 globin genes are expressed normally in bdh2 morphants; this keeps the term downstream/non-core.
Reason: Hemoglobin biosynthesis is a downstream erythroid phenotype of impaired siderophore/heme metabolism.
Supporting Evidence:
PMID:20550936
zebrafish embryos fail to synthesize
PMID:26929344
results in heme deficiency and delays erythroid maturation
file:DANRE/bdh2/bdh2-deep-research-falcon.md
globin genes (**hbae1/hbae3**) were reported as expressed normally, suggesting the phenotype reflects impaired heme/iron handling rather than globin transcription
|
|
GO:0043249
erythrocyte maturation
|
IMP
PMID:26929344 Inactivation of 3-hydroxybutyrate dehydrogenase 2 delays zeb... |
KEEP AS NON CORE |
Summary: erythrocyte maturation (GO:0043249) is supported or plausible for zebrafish bdh2, but it is not the most informative core function. Falcon deep research details the mechanism, namely that bdh2 loss causes mitochondrial dysfunction followed by premature mitochondrial clearance via mitophagy, and that suppressing autophagy via atg7 knockdown partially rescues maturation, confirming erythrocyte maturation is a downstream developmental consequence.
Reason: Erythrocyte maturation is a downstream developmental consequence of bdh2 inactivation.
Supporting Evidence:
PMID:26929344
results in heme deficiency and delays erythroid maturation
file:DANRE/bdh2/bdh2-deep-research-falcon.md
loss of bdh2 causes mitochondrial dysfunction followed by **premature mitochondrial clearance via mitophagy**
file:DANRE/bdh2/bdh2-deep-research-falcon.md
suppressing autophagy via **atg7** knockdown reduces mitochondrial clearance and partially rescues hemoglobinization and N:C ratios
|
|
GO:0042541
hemoglobin biosynthetic process
|
IMP
PMID:20550936 A mammalian siderophore synthesized by an enzyme with a bact... |
KEEP AS NON CORE |
Summary: hemoglobin biosynthetic process (GO:0042541) is supported or plausible for zebrafish bdh2, but it is not the most informative core function. Falcon deep research clarifies that the hypochromic/hemoglobinization phenotype reflects impaired heme/iron handling rather than globin transcription, since hbae1/hbae3 globin genes are expressed normally in bdh2 morphants; this keeps the term downstream/non-core.
Reason: Hemoglobin biosynthesis is a downstream erythroid phenotype of impaired siderophore/heme metabolism.
Supporting Evidence:
PMID:20550936
zebrafish embryos fail to synthesize
PMID:26929344
results in heme deficiency and delays erythroid maturation
file:DANRE/bdh2/bdh2-deep-research-falcon.md
globin genes (**hbae1/hbae3**) were reported as expressed normally, suggesting the phenotype reflects impaired heme/iron handling rather than globin transcription
|
|
GO:0016628
oxidoreductase activity, acting on the CH-CH group of donors, NAD or NADP as acceptor
|
ISS
GO_REF:0000024 |
MODIFY |
Summary: oxidoreductase activity, acting on the CH-CH group of donors, NAD or NADP as acceptor (GO:0016628) captures the right general area for zebrafish bdh2, but 4-oxoproline reductase activity (GO:0016617) is the better supported term.
Reason: The broad oxidoreductase activity should be replaced with the specific 4-oxoproline reductase activity.
Proposed replacements:
4-oxoproline reductase activity
Supporting Evidence:
file:DANRE/bdh2/bdh2-uniprot.txt
conversion of 4-oxo-L-proline to cis-4-hydroxy-L-proline
|
|
GO:0019290
siderophore biosynthetic process
|
ISS
GO_REF:0000024 |
ACCEPT |
Summary: siderophore biosynthetic process (GO:0019290) is supported for zebrafish bdh2 and is coherent with the synthesized gene function. Falcon deep research reinforces this as the central conserved role, identifying Bdh2 as the rate-limiting NAD-dependent enzyme of 2,5-DHBA (endogenous catecholate siderophore) biosynthesis and a functional homolog of bacterial EntA.
Reason: Siderophore biosynthesis is a central supported role of Bdh2/BDH2.
Supporting Evidence:
file:DANRE/bdh2/bdh2-uniprot.txt
formation of 2,5-dihydroxybenzoate (2,5-DHBA)
PMID:20550936
The iron-binding moiety of the mammalian siderophore is 2,5-DHBA
file:DANRE/bdh2/bdh2-deep-research-falcon.md
BDH2 catalyzes a **rate-limiting NAD-dependent step** in biosynthesis of **2,5-dihydroxybenzoic acid (2,5-DHBA)**, an endogenous catecholate that can coordinate iron
file:DANRE/bdh2/bdh2-deep-research-falcon.md
BDH2 is a functional homolog of **bacterial EntA**, linking its enzymology to catecholate siderophore chemistry
|
|
GO:0042168
heme metabolic process
|
IMP
PMID:20550936 A mammalian siderophore synthesized by an enzyme with a bact... |
ACCEPT |
Summary: heme metabolic process (GO:0042168) is supported for zebrafish bdh2 and is coherent with the synthesized gene function. Falcon deep research supports this via the pathway whereby Bdh2-derived 2,5-DHBA provides mitochondrial iron for heme synthesis, with the zebrafish hemoglobinization defect reflecting impaired heme/iron handling rather than globin transcription.
Reason: Heme metabolic process is directly supported by siderophore-dependent mitochondrial iron delivery and zebrafish heme-deficiency phenotypes.
Supporting Evidence:
PMID:20550936
zebrafish embryos fail to synthesize
PMID:26929344
results in heme deficiency and delays erythroid maturation
file:DANRE/bdh2/bdh2-deep-research-falcon.md
globin genes (**hbae1/hbae3**) were reported as expressed normally, suggesting the phenotype reflects impaired heme/iron handling rather than globin transcription
|
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
The literature retrieved specifically studies zebrafish bdh2 (3-hydroxybutyrate dehydrogenase 2; SDR family member) using bdh2-targeting morpholinos and bdh2 mRNA rescue, with phenotypes in erythrocytes/embryos (hypohemoglobinization, delayed erythroid maturation). This matches the UniProt target (Q561X9; SDR family; gene name bdh2) rather than the mitochondrial ketone-body enzyme BDH1 (which is explicitly distinguished as a different protein in the ortholog literature). (devireddy2010amammaliansiderophore pages 7-8, liu2014endogenoussiderophore25dihydroxybenzoic pages 9-10, davuluri2016inactivationof3hydroxybutyrate pages 3-5)
BDH2 (SDR family member 6) is a member of the SDR superfamily, which generally uses NAD(H) or NADP(H) as redox cofactors and typically relies on a conserved active-site Tyr for catalysis. In the BDH2 system described below, mutation of the catalytic Tyr eliminates the observed NAD-dependent oxidation activity. (devireddy2010amammaliansiderophore pages 2-3, liu2014endogenoussiderophore25dihydroxybenzoic pages 1-2)
Historically, the name “3-hydroxybutyrate dehydrogenase 2” created ambiguity with ketone-body metabolism. However, multiple lines of evidence support that BDH2’s primary conserved role is intracellular iron handling through synthesis of an endogenous siderophore-like molecule (2,5-DHBA), rather than bulk ketone-body oxidation. In particular, BDH2 is described as only ~20% identical to mitochondrial BDH1 and is considered dispensable for ketone-body metabolism in vivo in the mouse knockout study. (liu2014endogenoussiderophore25dihydroxybenzoic pages 9-10, liu2014endogenoussiderophore25dihydroxybenzoic pages 1-2)
A central current model is that BDH2 catalyzes a rate-limiting NAD-dependent step in biosynthesis of 2,5-dihydroxybenzoic acid (2,5-DHBA), an endogenous catecholate that can coordinate iron. BDH2 is a functional homolog of bacterial EntA, linking its enzymology to catecholate siderophore chemistry. BDH2-dependent siderophore depletion (in cells, yeast, and zebrafish) is associated with heme deficiency and impaired mitochondrial iron-dependent functions. (liu2014endogenoussiderophore25dihydroxybenzoic pages 1-2, pantopoulos2012mechanismsofmammalian pages 9-11)
Devireddy et al. (Cell; 2010-06, https://doi.org/10.1016/j.cell.2010.04.040) present biochemical evidence that recombinant BDH2 catalyzes an NAD+-dependent oxidation analogous to bacterial EntA’s chemistry, assayed as oxidation of 2,3-diDHBA to 2,3-DHBA with NAD → NADH, and that mutation of an active-site Tyr (Tyr→Phe) abolishes activity. (devireddy2010amammaliansiderophore pages 2-3)
The same Cell 2010 study identifies 2,5-DHBA associated with the mammalian iron-trafficking lipocalin 24p3 (LCN2/NGAL) and shows that 2,5-DHBA and related ligands can enable 24p3 to bind iron. Reported ligand-binding affinities are approximately ~12 nM for 2,5-DHBA and ~8 nM for 2,3-DHBA. (devireddy2010amammaliansiderophore pages 2-3)
Interpretation for zebrafish annotation: even though the enzymatic assay used 2,3-diDHBA/2,3-DHBA readouts in the biochemical system, zebrafish phenotypes and rescue by 2,5-DHBA (below) support that the physiologically relevant pathway output in vivo is 2,5-DHBA-dependent iron delivery to mitochondrial utilization (heme synthesis). (davuluri2016inactivationof3hydroxybutyrate pages 3-5, davuluri2016inactivationof3hydroxybutyrate pages 6-8)
In zebrafish erythrocytes, loss of bdh2 causes mitochondrial dysfunction followed by premature mitochondrial clearance via mitophagy, implying that BDH2 activity is functionally upstream of maintaining mitochondria during erythroid maturation (via mitochondrial iron/heme availability). (davuluri2016inactivationof3hydroxybutyrate pages 3-5, davuluri2016inactivationof3hydroxybutyrate pages 6-8)
A 2024 study (preprint; 2024-10, https://doi.org/10.21203/rs.3.rs-5345588/v1) proposes that BDH2 localizes to the outer mitochondrial membrane and is enriched at mitochondria–lysosome contact sites (MLCs), where it generates 2,5-DHBA to mediate lysosome-to-mitochondria iron transfer. This work also supports a pH-dependent iron-binding mechanism for 2,5-DHBA: NMR-based observations indicate 2,5-DHBA binds Fe(III) and Fe(II) at neutral pH, with Fe(III) complexes remaining stable under acidic conditions, consistent with iron capture in lysosomes and release near mitochondria. (agostinis2024abdh2drivenlysosome pages 9-11)
Caution for annotation: the MLC localization is not (yet) demonstrated directly in zebrafish in the evidence retrieved here; it should be treated as ortholog-informed localization. (agostinis2024abdh2drivenlysosome pages 9-11)
In zebrafish embryos, bdh2 morpholino knockdown causes hypochromic blood and markedly reduced o-dianisidine staining (a hemoglobin/heme-associated stain). Two independent bdh2 morpholinos produced the phenotype, and mRNA rescue with bdh2 restored staining. Importantly, globin genes (hbae1/hbae3) were reported as expressed normally, suggesting the phenotype reflects impaired heme/iron handling rather than globin transcription. (devireddy2010amammaliansiderophore pages 7-8, devireddy2010amammaliansiderophore pages 11-11)
Davuluri et al. (PNAS; 2016-02, https://doi.org/10.1073/pnas.1600077113) provide a mechanistic zebrafish study:
Figures quantifying N:C ratios and o-dianisidine rescue are available in the retrieved figure crops. (davuluri2016inactivationof3hydroxybutyrate media 10869607, davuluri2016inactivationof3hydroxybutyrate media de8cd0a0, davuluri2016inactivationof3hydroxybutyrate media d6e61517)
The integrated zebrafish evidence supports the pathway:
Bdh2 → 2,5-DHBA (endogenous siderophore-like ligand) → mitochondrial iron availability → heme synthesis & mitochondrial function → appropriate timing of mitophagy during erythropoiesis → erythroid maturation/hemoglobinization. (davuluri2016inactivationof3hydroxybutyrate pages 3-5, davuluri2016inactivationof3hydroxybutyrate pages 6-8)
Agostinis et al. (preprint; 2024-10, https://doi.org/10.21203/rs.3.rs-5345588/v1) extends the siderophore model into a spatially explicit trafficking mechanism:
Relevance to zebrafish functional annotation: while mechanistic subcellular localization is ortholog-based, the model provides a plausible cellular explanation for zebrafish erythrocyte phenotypes (mitochondrial iron/heme deficit leading to mitochondrial dysfunction and altered mitophagy timing). (davuluri2016inactivationof3hydroxybutyrate pages 3-5, agostinis2024abdh2drivenlysosome pages 9-11)
A 2023 review on ferroptosis in AML discusses BDH2 as an iron-handling factor that may reduce cytoplasmic free iron and lipid peroxidation, potentially lowering ferroptosis susceptibility; it contrasts this with LCN2/24p3-associated pathways that can increase iron load. This is largely interpretive and disease-contextual rather than zebrafish-specific. (zhang2023susceptibilityofacute pages 6-8)
The zebrafish bdh2 morphant phenotype (hypohemoglobinization with preserved globin gene expression) demonstrates a tractable in vivo model to study mitochondrial iron utilization and heme synthesis and how mitochondrial dysfunction feeds into mitophagy timing during erythropoiesis. This has practical value for screening modifiers of iron/heme pathways or autophagy-dependent erythroid maturation. (devireddy2010amammaliansiderophore pages 7-8, davuluri2016inactivationof3hydroxybutyrate pages 3-5, davuluri2016inactivationof3hydroxybutyrate pages 6-8)
The 2024 mechanistic work suggests BDH2/2,5-DHBA-dependent organellar iron redistribution is actionable in contexts where ferroptosis sensitivity is clinically relevant (e.g., drug-tolerant cancer cell states), although this evidence is from mammalian cancer models and should not be overextended to zebrafish physiology without additional direct validation. (agostinis2024abdh2drivenlysosome pages 1-5, agostinis2024abdh2drivenlysosome pages 9-11)
The following evidence table compiles the most directly supported claims for functional annotation.
| Claim/Observation | Species/System | Experimental approach | Key quantitative data | Interpretation for function/localization/pathway | Primary citation (with DOI/URL + year) |
|---|---|---|---|---|---|
| bdh2 knockdown causes heme/hemoglobin deficiency in zebrafish embryos; phenotype is rescued by MO-resistant bdh2 mRNA while globin transcripts remain normal | Danio rerio embryos | Morpholino knockdown, RT-PCR confirmation of aberrant splicing, whole-mount o-dianisidine staining, isolated blood cell staining, mRNA rescue | Qualitative but replicated phenotype: marked reduction in o-dianisidine staining; second independent MO gave the same result; rescue restored normal staining; no reported reduction of hbae1/hbae3 expression | Supports that zebrafish Bdh2 is required for heme biosynthesis/iron handling rather than globin gene transcription; consistent with a conserved siderophore-mediated mitochondrial iron delivery role rather than canonical ketone-body metabolism (devireddy2010amammaliansiderophore pages 7-8, devireddy2010amammaliansiderophore pages 11-11) | Devireddy et al., Cell (2010), DOI: 10.1016/j.cell.2010.04.040, URL: https://doi.org/10.1016/j.cell.2010.04.040 |
| Bdh2 enzymatic activity is NAD+-dependent oxidation of a dihydro-DHBA precursor to DHBA; DHBA binds 24p3 with high affinity | Recombinant mammalian BDH2 / 24p3 system | Enzyme assay with recombinant BDH2, catalytic Tyr mutant, NAD to NADH conversion assay, ligand-binding assays | 24p3 binding affinities reported at ~12 nM for 2,5-DHBA and ~8 nM for 2,3-DHBA; Tyr147/Phe mutation abolished activity | Strong biochemical evidence that BDH2 participates in endogenous catecholate siderophore production; links enzyme activity to iron trafficking via 24p3-bound DHBA, implying a cytosolic iron-chaperoning pathway connected to mitochondrial iron use (devireddy2010amammaliansiderophore pages 2-3) | Devireddy et al., Cell (2010), DOI: 10.1016/j.cell.2010.04.040, URL: https://doi.org/10.1016/j.cell.2010.04.040 |
| bdh2 inactivation delays zebrafish erythroid maturation and causes hypohemoglobinization; rescue by bdh2 mRNA and by 2,5-DHBA | Danio rerio erythrocytes/embryos | Morpholino knockdown, o-dianisidine staining, May-Grunwald/Giemsa morphology, N:C ratio quantification, mRNA rescue, 2,5-DHBA supplementation, iron dextran bypass tests | N:C ratio quantified on 300 cells (mean ± SD, P < 0.05); constitutive respiration ~3-fold lower and uncoupled respiration ~2.18-fold lower in morphants; o-dianisidine staining partially rescued by bdh2 mRNA and by 2,5-DHBA; iron dextran failed to rescue mitochondrial iron deficiency | Indicates Bdh2 acts upstream of mitochondrial iron utilization in erythroid cells, with 2,5-DHBA as functional mediator; supports a pathway of siderophore-dependent mitochondrial iron import required for heme synthesis and erythroid maturation (davuluri2016inactivationof3hydroxybutyrate pages 2-3, davuluri2016inactivationof3hydroxybutyrate pages 3-5, davuluri2016inactivationof3hydroxybutyrate media 10869607) | Davuluri et al., PNAS (2016), DOI: 10.1073/pnas.1600077113, URL: https://doi.org/10.1073/pnas.1600077113 |
| Loss of bdh2 triggers premature mitophagy in zebrafish erythrocytes; blocking autophagy partially rescues maturation/hemoglobinization | Danio rerio erythrocytes | Confocal MitoTracker/LysoTracker imaging, electron microscopy, anti-OXPHOS staining, atg7 morpholino coinjection, transcriptome/GSEA | Mitochondrial counts quantified on 50 cells (mean ± SD, P < 0.05); N:C ratio quantified on 300 cells (P < 0.05); suppression of atg7 reduced mitochondrial clearance and partially rescued o-dianisidine staining/maturation | Places Bdh2 function at the intersection of mitochondrial iron metabolism and erythroid organelle clearance: siderophore depletion causes mitochondrial dysfunction, which drives premature mitophagy and delayed maturation (davuluri2016inactivationof3hydroxybutyrate pages 6-8, davuluri2016inactivationof3hydroxybutyrate pages 8-9) | Davuluri et al., PNAS (2016), DOI: 10.1073/pnas.1600077113, URL: https://doi.org/10.1073/pnas.1600077113 |
| BDH2 is dispensable for bulk ketone-body metabolism in vivo but required for endogenous siderophore/iron homeostasis; bdh2-null mice show anemia and splenic iron overload, partially rescued by 2,5-DHBA | Mouse (bdh2 knockout) with cross-reference to zebrafish/yeast/cultured cells | Gene knockout, iron phenotyping, supplementation with 2,5-DHBA, comparative interpretation with prior zebrafish knockdown work | No numeric values in provided excerpt; reported outcomes include microcytic anemia, reduced serum iron, splenic iron overload, and partial rescue by 2,5-DHBA supplementation | Supports current view that BDH2’s primary conserved role is in siderophore-dependent intracellular iron trafficking and heme biology, not canonical cytosolic ketone oxidation; zebrafish phenotype is therefore mechanistically coherent with mammalian knockout data (liu2014endogenoussiderophore25dihydroxybenzoic pages 9-10, liu2014endogenoussiderophore25dihydroxybenzoic pages 1-2) | Liu et al., Molecular and Cellular Biology (2014), DOI: 10.1128/MCB.00231-14, URL: https://doi.org/10.1128/MCB.00231-14 |
Table: This table compiles the strongest primary evidence supporting functional annotation of zebrafish bdh2/BDH2 (UniProt Q561X9), integrating zebrafish phenotypes with biochemical and mammalian ortholog data. It is useful for distinguishing the best-supported role in siderophore-dependent iron/heme metabolism from weaker ketone-metabolism annotations.
Primary supported molecular function: SDR enzyme catalyzing an NAD-dependent oxidation step in endogenous catecholate (DHBA) biosynthesis, required for production of 2,5-DHBA, an iron-binding ligand central to intracellular/organellar iron trafficking. (devireddy2010amammaliansiderophore pages 2-3, liu2014endogenoussiderophore25dihydroxybenzoic pages 1-2)
Primary supported biological process in zebrafish: supports mitochondrial iron utilization and heme/hemoglobinization during erythropoiesis; loss causes heme deficiency, delayed erythroid maturation, mitochondrial dysfunction, and premature mitophagy, with rescue by bdh2 mRNA and 2,5-DHBA and partial rescue by reducing autophagy (atg7). (devireddy2010amammaliansiderophore pages 7-8, davuluri2016inactivationof3hydroxybutyrate pages 3-5, davuluri2016inactivationof3hydroxybutyrate pages 6-8)
Most likely cellular localization (best current mechanistic model; ortholog-informed): cytosolic/outer-mitochondrial-membrane-associated enzyme enriched at mitochondria–lysosome contact sites coordinating lysosome-to-mitochondria iron transfer via 2,5-DHBA. (agostinis2024abdh2drivenlysosome pages 9-11)
Despite the request to prioritize 2023–2024, direct zebrafish bdh2 functional studies retrieved here are primarily 2010 and 2016, whereas 2023–2024 advances are mainly mechanistic extensions in mammalian systems and interpretive reviews. Therefore, zebrafish conclusions are strongly evidence-based but not “recent,” and recent mechanistic localization (MLCs) should be treated as ortholog-informed until directly validated in zebrafish tissues. (devireddy2010amammaliansiderophore pages 7-8, davuluri2016inactivationof3hydroxybutyrate pages 3-5, agostinis2024abdh2drivenlysosome pages 9-11)
References
(devireddy2010amammaliansiderophore pages 7-8): Laxminarayana R. Devireddy, Daniel O. Hart, David H. Goetz, and Michael R. Green. A mammalian siderophore synthesized by an enzyme with a bacterial homolog involved in enterobactin production. Cell, 141:1006-1017, Jun 2010. URL: https://doi.org/10.1016/j.cell.2010.04.040, doi:10.1016/j.cell.2010.04.040. This article has 370 citations and is from a highest quality peer-reviewed journal.
(liu2014endogenoussiderophore25dihydroxybenzoic pages 9-10): Zhuoming Liu, Alieta Ciocea, and L. Devireddy. Endogenous siderophore 2,5-dihydroxybenzoic acid deficiency promotes anemia and splenic iron overload in mice. Molecular and Cellular Biology, 34:2533-2546, Jul 2014. URL: https://doi.org/10.1128/mcb.00231-14, doi:10.1128/mcb.00231-14. This article has 49 citations and is from a domain leading peer-reviewed journal.
(davuluri2016inactivationof3hydroxybutyrate pages 3-5): Gangarao Davuluri, Ping Song, Zhuoming Liu, David Wald, Takuya F. Sakaguchi, Michael R. Green, and L. Devireddy. Inactivation of 3-hydroxybutyrate dehydrogenase 2 delays zebrafish erythroid maturation by conferring premature mitophagy. Proceedings of the National Academy of Sciences, 113:E1460-E1469, Feb 2016. URL: https://doi.org/10.1073/pnas.1600077113, doi:10.1073/pnas.1600077113. This article has 30 citations and is from a highest quality peer-reviewed journal.
(devireddy2010amammaliansiderophore pages 2-3): Laxminarayana R. Devireddy, Daniel O. Hart, David H. Goetz, and Michael R. Green. A mammalian siderophore synthesized by an enzyme with a bacterial homolog involved in enterobactin production. Cell, 141:1006-1017, Jun 2010. URL: https://doi.org/10.1016/j.cell.2010.04.040, doi:10.1016/j.cell.2010.04.040. This article has 370 citations and is from a highest quality peer-reviewed journal.
(liu2014endogenoussiderophore25dihydroxybenzoic pages 1-2): Zhuoming Liu, Alieta Ciocea, and L. Devireddy. Endogenous siderophore 2,5-dihydroxybenzoic acid deficiency promotes anemia and splenic iron overload in mice. Molecular and Cellular Biology, 34:2533-2546, Jul 2014. URL: https://doi.org/10.1128/mcb.00231-14, doi:10.1128/mcb.00231-14. This article has 49 citations and is from a domain leading peer-reviewed journal.
(pantopoulos2012mechanismsofmammalian pages 9-11): Kostas Pantopoulos, Suheel Kumar Porwal, Alan Tartakoff, and L. Devireddy. Mechanisms of mammalian iron homeostasis. Biochemistry, 51 29:5705-24, Jul 2012. URL: https://doi.org/10.1021/bi300752r, doi:10.1021/bi300752r. This article has 793 citations and is from a peer-reviewed journal.
(davuluri2016inactivationof3hydroxybutyrate pages 6-8): Gangarao Davuluri, Ping Song, Zhuoming Liu, David Wald, Takuya F. Sakaguchi, Michael R. Green, and L. Devireddy. Inactivation of 3-hydroxybutyrate dehydrogenase 2 delays zebrafish erythroid maturation by conferring premature mitophagy. Proceedings of the National Academy of Sciences, 113:E1460-E1469, Feb 2016. URL: https://doi.org/10.1073/pnas.1600077113, doi:10.1073/pnas.1600077113. This article has 30 citations and is from a highest quality peer-reviewed journal.
(agostinis2024abdh2drivenlysosome pages 9-11): Patrizia Agostinis, Francesca Rizzollo, Abril Escamilla-Ayala, Nicola Fattorelli, Natalia Lysiak, Sanket More, Lucia Barazzuol, Chris Van den Haute, Joris Van Asselberghs, David Nittner, Jonathan Coene, Vivek Venkataramani, Bernhard Michalke, Christine Gaillet, Tatiana Cañeque, Irwin Davidson, Steven Verhelst, Peter Vangheluwe, Tito Calì, Jean Christophe Marine, Raphaël Rodriguez, and Julie Bonnereau. A bdh2-driven lysosome to mitochondria iron trafficking controls ferroptosis in melanoma. Unknown journal, Oct 2024. URL: https://doi.org/10.21203/rs.3.rs-5345588/v1, doi:10.21203/rs.3.rs-5345588/v1.
(devireddy2010amammaliansiderophore pages 11-11): Laxminarayana R. Devireddy, Daniel O. Hart, David H. Goetz, and Michael R. Green. A mammalian siderophore synthesized by an enzyme with a bacterial homolog involved in enterobactin production. Cell, 141:1006-1017, Jun 2010. URL: https://doi.org/10.1016/j.cell.2010.04.040, doi:10.1016/j.cell.2010.04.040. This article has 370 citations and is from a highest quality peer-reviewed journal.
(davuluri2016inactivationof3hydroxybutyrate pages 2-3): Gangarao Davuluri, Ping Song, Zhuoming Liu, David Wald, Takuya F. Sakaguchi, Michael R. Green, and L. Devireddy. Inactivation of 3-hydroxybutyrate dehydrogenase 2 delays zebrafish erythroid maturation by conferring premature mitophagy. Proceedings of the National Academy of Sciences, 113:E1460-E1469, Feb 2016. URL: https://doi.org/10.1073/pnas.1600077113, doi:10.1073/pnas.1600077113. This article has 30 citations and is from a highest quality peer-reviewed journal.
(davuluri2016inactivationof3hydroxybutyrate media 10869607): Gangarao Davuluri, Ping Song, Zhuoming Liu, David Wald, Takuya F. Sakaguchi, Michael R. Green, and L. Devireddy. Inactivation of 3-hydroxybutyrate dehydrogenase 2 delays zebrafish erythroid maturation by conferring premature mitophagy. Proceedings of the National Academy of Sciences, 113:E1460-E1469, Feb 2016. URL: https://doi.org/10.1073/pnas.1600077113, doi:10.1073/pnas.1600077113. This article has 30 citations and is from a highest quality peer-reviewed journal.
(davuluri2016inactivationof3hydroxybutyrate media de8cd0a0): Gangarao Davuluri, Ping Song, Zhuoming Liu, David Wald, Takuya F. Sakaguchi, Michael R. Green, and L. Devireddy. Inactivation of 3-hydroxybutyrate dehydrogenase 2 delays zebrafish erythroid maturation by conferring premature mitophagy. Proceedings of the National Academy of Sciences, 113:E1460-E1469, Feb 2016. URL: https://doi.org/10.1073/pnas.1600077113, doi:10.1073/pnas.1600077113. This article has 30 citations and is from a highest quality peer-reviewed journal.
(davuluri2016inactivationof3hydroxybutyrate media d6e61517): Gangarao Davuluri, Ping Song, Zhuoming Liu, David Wald, Takuya F. Sakaguchi, Michael R. Green, and L. Devireddy. Inactivation of 3-hydroxybutyrate dehydrogenase 2 delays zebrafish erythroid maturation by conferring premature mitophagy. Proceedings of the National Academy of Sciences, 113:E1460-E1469, Feb 2016. URL: https://doi.org/10.1073/pnas.1600077113, doi:10.1073/pnas.1600077113. This article has 30 citations and is from a highest quality peer-reviewed journal.
(agostinis2024abdh2drivenlysosome pages 1-5): Patrizia Agostinis, Francesca Rizzollo, Abril Escamilla-Ayala, Nicola Fattorelli, Natalia Lysiak, Sanket More, Lucia Barazzuol, Chris Van den Haute, Joris Van Asselberghs, David Nittner, Jonathan Coene, Vivek Venkataramani, Bernhard Michalke, Christine Gaillet, Tatiana Cañeque, Irwin Davidson, Steven Verhelst, Peter Vangheluwe, Tito Calì, Jean Christophe Marine, Raphaël Rodriguez, and Julie Bonnereau. A bdh2-driven lysosome to mitochondria iron trafficking controls ferroptosis in melanoma. Unknown journal, Oct 2024. URL: https://doi.org/10.21203/rs.3.rs-5345588/v1, doi:10.21203/rs.3.rs-5345588/v1.
(zhang2023susceptibilityofacute pages 6-8): Hanyun Zhang, Chunjie Sun, Qi Sun, Ye Li, Chao Zhou, and Changgang Sun. Susceptibility of acute myeloid leukemia cells to ferroptosis and evasion strategies. Frontiers in Molecular Biosciences, Sep 2023. URL: https://doi.org/10.3389/fmolb.2023.1275774, doi:10.3389/fmolb.2023.1275774. This article has 30 citations.
(davuluri2016inactivationof3hydroxybutyrate pages 8-9): Gangarao Davuluri, Ping Song, Zhuoming Liu, David Wald, Takuya F. Sakaguchi, Michael R. Green, and L. Devireddy. Inactivation of 3-hydroxybutyrate dehydrogenase 2 delays zebrafish erythroid maturation by conferring premature mitophagy. Proceedings of the National Academy of Sciences, 113:E1460-E1469, Feb 2016. URL: https://doi.org/10.1073/pnas.1600077113, doi:10.1073/pnas.1600077113. This article has 30 citations and is from a highest quality peer-reviewed journal.
id: Q561X9
gene_symbol: bdh2
product_type: PROTEIN
status: DRAFT
taxon:
id: NCBITaxon:7955
label: Danio rerio
description: bdh2 encodes a cytosolic short-chain dehydrogenase/reductase implicated in mammalian/eukaryotic siderophore biogenesis,
mitochondrial iron delivery, heme synthesis, and erythroid maturation in zebrafish. The core review distinguishes the specific
4-oxoproline reductase detoxification activity from the separate 2,5-DHBA-associated siderophore/heme role, while 3-hydroxybutyrate
dehydrogenase activity is treated as a possible secondary/by-similarity activity rather than the main zebrafish functional theme.
existing_annotations:
- term:
id: GO:0003858
label: 3-hydroxybutyrate dehydrogenase activity
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: 3-hydroxybutyrate dehydrogenase activity (GO:0003858) is supported or plausible for zebrafish bdh2, but it is
not the most informative core function. Falcon deep research reinforces keeping this non-core, noting BDH2 is only ~20%
identical to mitochondrial BDH1 and is considered dispensable for bulk ketone-body metabolism in vivo, with its conserved
role being siderophore-dependent iron handling rather than ketone oxidation.
action: KEEP_AS_NON_CORE
reason: 3-hydroxybutyrate dehydrogenase activity is described as a possible/by-similarity activity and is not the main
zebrafish siderophore/heme function.
supported_by:
- reference_id: file:DANRE/bdh2/bdh2-uniprot.txt
supporting_text: hydroxybutyrate dehydrogenase (By similarity).
- reference_id: file:DANRE/bdh2/bdh2-deep-research-falcon.md
supporting_text: |
is described as only ~20% identical to mitochondrial BDH1 and is considered dispensable for ketone-body metabolism in vivo in the mouse knockout study
- term:
id: GO:0005737
label: cytoplasm
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: cytoplasm (GO:0005737) is supported for zebrafish bdh2 and is coherent with the synthesized gene function.
action: ACCEPT
reason: The cytoplasmic location is supported.
supported_by:
- reference_id: file:DANRE/bdh2/bdh2-uniprot.txt
supporting_text: 'SUBCELLULAR LOCATION: Cytoplasm'
- term:
id: GO:0019290
label: siderophore biosynthetic process
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: siderophore biosynthetic process (GO:0019290) is supported for zebrafish bdh2 and is coherent with the synthesized
gene function. Falcon deep research reinforces this as the central conserved role, identifying Bdh2 as the rate-limiting
NAD-dependent enzyme of 2,5-DHBA (endogenous catecholate siderophore) biosynthesis and a functional homolog of bacterial EntA.
action: ACCEPT
reason: Siderophore biosynthesis is a central supported role of Bdh2/BDH2.
supported_by:
- reference_id: file:DANRE/bdh2/bdh2-uniprot.txt
supporting_text: formation of 2,5-dihydroxybenzoate (2,5-DHBA)
- reference_id: PMID:20550936
supporting_text: The iron-binding moiety of the mammalian siderophore is 2,5-DHBA
- reference_id: file:DANRE/bdh2/bdh2-deep-research-falcon.md
supporting_text: |
BDH2 catalyzes a **rate-limiting NAD-dependent step** in biosynthesis of **2,5-dihydroxybenzoic acid (2,5-DHBA)**, an endogenous catecholate that can coordinate iron
- reference_id: file:DANRE/bdh2/bdh2-deep-research-falcon.md
supporting_text: |
BDH2 is a functional homolog of **bacterial EntA**, linking its enzymology to catecholate siderophore chemistry
- term:
id: GO:0003858
label: 3-hydroxybutyrate dehydrogenase activity
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: 3-hydroxybutyrate dehydrogenase activity (GO:0003858) is supported or plausible for zebrafish bdh2, but it is
not the most informative core function. Falcon deep research reinforces keeping this non-core, noting BDH2 is only ~20%
identical to mitochondrial BDH1 and is considered dispensable for bulk ketone-body metabolism in vivo, with its conserved
role being siderophore-dependent iron handling rather than ketone oxidation.
action: KEEP_AS_NON_CORE
reason: 3-hydroxybutyrate dehydrogenase activity is described as a possible/by-similarity activity and is not the main
zebrafish siderophore/heme function.
supported_by:
- reference_id: file:DANRE/bdh2/bdh2-uniprot.txt
supporting_text: hydroxybutyrate dehydrogenase (By similarity).
- reference_id: file:DANRE/bdh2/bdh2-deep-research-falcon.md
supporting_text: |
is described as only ~20% identical to mitochondrial BDH1 and is considered dispensable for ketone-body metabolism in vivo in the mouse knockout study
- term:
id: GO:0005737
label: cytoplasm
evidence_type: IEA
original_reference_id: GO_REF:0000044
review:
summary: cytoplasm (GO:0005737) is supported for zebrafish bdh2 and is coherent with the synthesized gene function.
action: ACCEPT
reason: The cytoplasmic location is supported.
supported_by:
- reference_id: file:DANRE/bdh2/bdh2-uniprot.txt
supporting_text: 'SUBCELLULAR LOCATION: Cytoplasm'
- term:
id: GO:0016617
label: 4-oxoproline reductase activity
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: 4-oxoproline reductase activity (GO:0016617) is supported for zebrafish bdh2 and is coherent with the synthesized
gene function.
action: ACCEPT
reason: 4-oxoproline reductase activity is the specific UniProt catalytic activity for this SDR enzyme.
supported_by:
- reference_id: file:DANRE/bdh2/bdh2-uniprot.txt
supporting_text: conversion of 4-oxo-L-proline to cis-4-hydroxy-L-proline
- term:
id: GO:0003858
label: 3-hydroxybutyrate dehydrogenase activity
evidence_type: ISS
original_reference_id: GO_REF:0000024
review:
summary: 3-hydroxybutyrate dehydrogenase activity (GO:0003858) is supported or plausible for zebrafish bdh2, but it is
not the most informative core function. Falcon deep research reinforces keeping this non-core, noting BDH2 is only ~20%
identical to mitochondrial BDH1 and is considered dispensable for bulk ketone-body metabolism in vivo, with its conserved
role being siderophore-dependent iron handling rather than ketone oxidation.
action: KEEP_AS_NON_CORE
reason: 3-hydroxybutyrate dehydrogenase activity is described as a possible/by-similarity activity and is not the main
zebrafish siderophore/heme function.
supported_by:
- reference_id: file:DANRE/bdh2/bdh2-uniprot.txt
supporting_text: hydroxybutyrate dehydrogenase (By similarity).
- reference_id: file:DANRE/bdh2/bdh2-deep-research-falcon.md
supporting_text: |
is described as only ~20% identical to mitochondrial BDH1 and is considered dispensable for ketone-body metabolism in vivo in the mouse knockout study
- term:
id: GO:0005737
label: cytoplasm
evidence_type: ISS
original_reference_id: GO_REF:0000024
review:
summary: cytoplasm (GO:0005737) is supported for zebrafish bdh2 and is coherent with the synthesized gene function.
action: ACCEPT
reason: The cytoplasmic location is supported.
supported_by:
- reference_id: file:DANRE/bdh2/bdh2-uniprot.txt
supporting_text: 'SUBCELLULAR LOCATION: Cytoplasm'
- term:
id: GO:0016617
label: 4-oxoproline reductase activity
evidence_type: ISS
original_reference_id: GO_REF:0000024
review:
summary: 4-oxoproline reductase activity (GO:0016617) is supported for zebrafish bdh2 and is coherent with the synthesized
gene function.
action: ACCEPT
reason: 4-oxoproline reductase activity is the specific UniProt catalytic activity for this SDR enzyme.
supported_by:
- reference_id: file:DANRE/bdh2/bdh2-uniprot.txt
supporting_text: conversion of 4-oxo-L-proline to cis-4-hydroxy-L-proline
- term:
id: GO:0042541
label: hemoglobin biosynthetic process
evidence_type: IMP
original_reference_id: PMID:26929344
review:
summary: hemoglobin biosynthetic process (GO:0042541) is supported or plausible for zebrafish bdh2, but it is not the
most informative core function. Falcon deep research clarifies that the hypochromic/hemoglobinization phenotype reflects
impaired heme/iron handling rather than globin transcription, since hbae1/hbae3 globin genes are expressed normally
in bdh2 morphants; this keeps the term downstream/non-core.
action: KEEP_AS_NON_CORE
reason: Hemoglobin biosynthesis is a downstream erythroid phenotype of impaired siderophore/heme metabolism.
supported_by:
- reference_id: PMID:20550936
supporting_text: zebrafish embryos fail to synthesize
- reference_id: PMID:26929344
supporting_text: results in heme deficiency and delays erythroid maturation
- reference_id: file:DANRE/bdh2/bdh2-deep-research-falcon.md
supporting_text: |
globin genes (**hbae1/hbae3**) were reported as expressed normally, suggesting the phenotype reflects impaired heme/iron handling rather than globin transcription
- term:
id: GO:0043249
label: erythrocyte maturation
evidence_type: IMP
original_reference_id: PMID:26929344
review:
summary: erythrocyte maturation (GO:0043249) is supported or plausible for zebrafish bdh2, but it is not the most informative
core function. Falcon deep research details the mechanism, namely that bdh2 loss causes mitochondrial dysfunction
followed by premature mitochondrial clearance via mitophagy, and that suppressing autophagy via atg7 knockdown partially
rescues maturation, confirming erythrocyte maturation is a downstream developmental consequence.
action: KEEP_AS_NON_CORE
reason: Erythrocyte maturation is a downstream developmental consequence of bdh2 inactivation.
supported_by:
- reference_id: PMID:26929344
supporting_text: results in heme deficiency and delays erythroid maturation
- reference_id: file:DANRE/bdh2/bdh2-deep-research-falcon.md
supporting_text: |
loss of bdh2 causes mitochondrial dysfunction followed by **premature mitochondrial clearance via mitophagy**
- reference_id: file:DANRE/bdh2/bdh2-deep-research-falcon.md
supporting_text: |
suppressing autophagy via **atg7** knockdown reduces mitochondrial clearance and partially rescues hemoglobinization and N:C ratios
- term:
id: GO:0042541
label: hemoglobin biosynthetic process
evidence_type: IMP
original_reference_id: PMID:20550936
review:
summary: hemoglobin biosynthetic process (GO:0042541) is supported or plausible for zebrafish bdh2, but it is not the
most informative core function. Falcon deep research clarifies that the hypochromic/hemoglobinization phenotype reflects
impaired heme/iron handling rather than globin transcription, since hbae1/hbae3 globin genes are expressed normally
in bdh2 morphants; this keeps the term downstream/non-core.
action: KEEP_AS_NON_CORE
reason: Hemoglobin biosynthesis is a downstream erythroid phenotype of impaired siderophore/heme metabolism.
supported_by:
- reference_id: PMID:20550936
supporting_text: zebrafish embryos fail to synthesize
- reference_id: PMID:26929344
supporting_text: results in heme deficiency and delays erythroid maturation
- reference_id: file:DANRE/bdh2/bdh2-deep-research-falcon.md
supporting_text: |
globin genes (**hbae1/hbae3**) were reported as expressed normally, suggesting the phenotype reflects impaired heme/iron handling rather than globin transcription
- term:
id: GO:0016628
label: oxidoreductase activity, acting on the CH-CH group of donors, NAD or NADP as acceptor
evidence_type: ISS
original_reference_id: GO_REF:0000024
review:
summary: oxidoreductase activity, acting on the CH-CH group of donors, NAD or NADP as acceptor (GO:0016628) captures the
right general area for zebrafish bdh2, but 4-oxoproline reductase activity (GO:0016617) is the better supported term.
action: MODIFY
reason: The broad oxidoreductase activity should be replaced with the specific 4-oxoproline reductase activity.
proposed_replacement_terms:
- id: GO:0016617
label: 4-oxoproline reductase activity
supported_by:
- reference_id: file:DANRE/bdh2/bdh2-uniprot.txt
supporting_text: conversion of 4-oxo-L-proline to cis-4-hydroxy-L-proline
- term:
id: GO:0019290
label: siderophore biosynthetic process
evidence_type: ISS
original_reference_id: GO_REF:0000024
review:
summary: siderophore biosynthetic process (GO:0019290) is supported for zebrafish bdh2 and is coherent with the synthesized
gene function. Falcon deep research reinforces this as the central conserved role, identifying Bdh2 as the rate-limiting
NAD-dependent enzyme of 2,5-DHBA (endogenous catecholate siderophore) biosynthesis and a functional homolog of bacterial EntA.
action: ACCEPT
reason: Siderophore biosynthesis is a central supported role of Bdh2/BDH2.
supported_by:
- reference_id: file:DANRE/bdh2/bdh2-uniprot.txt
supporting_text: formation of 2,5-dihydroxybenzoate (2,5-DHBA)
- reference_id: PMID:20550936
supporting_text: The iron-binding moiety of the mammalian siderophore is 2,5-DHBA
- reference_id: file:DANRE/bdh2/bdh2-deep-research-falcon.md
supporting_text: |
BDH2 catalyzes a **rate-limiting NAD-dependent step** in biosynthesis of **2,5-dihydroxybenzoic acid (2,5-DHBA)**, an endogenous catecholate that can coordinate iron
- reference_id: file:DANRE/bdh2/bdh2-deep-research-falcon.md
supporting_text: |
BDH2 is a functional homolog of **bacterial EntA**, linking its enzymology to catecholate siderophore chemistry
- term:
id: GO:0042168
label: heme metabolic process
evidence_type: IMP
original_reference_id: PMID:20550936
review:
summary: heme metabolic process (GO:0042168) is supported for zebrafish bdh2 and is coherent with the synthesized gene
function. Falcon deep research supports this via the pathway whereby Bdh2-derived 2,5-DHBA provides mitochondrial iron
for heme synthesis, with the zebrafish hemoglobinization defect reflecting impaired heme/iron handling rather than
globin transcription.
action: ACCEPT
reason: Heme metabolic process is directly supported by siderophore-dependent mitochondrial iron delivery and zebrafish
heme-deficiency phenotypes.
supported_by:
- reference_id: PMID:20550936
supporting_text: zebrafish embryos fail to synthesize
- reference_id: PMID:26929344
supporting_text: results in heme deficiency and delays erythroid maturation
- reference_id: file:DANRE/bdh2/bdh2-deep-research-falcon.md
supporting_text: |
globin genes (**hbae1/hbae3**) were reported as expressed normally, suggesting the phenotype reflects impaired heme/iron handling rather than globin transcription
references:
- id: GO_REF:0000024
title: Manual transfer of experimentally-verified manual GO annotation data to orthologs by curator judgment of sequence
similarity
findings: []
- id: GO_REF:0000033
title: Annotation inferences using phylogenetic trees
findings: []
- id: GO_REF:0000044
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative
changes to GO terms applied by UniProt
findings: []
- id: GO_REF:0000120
title: Combined Automated Annotation using Multiple IEA Methods
findings: []
- id: PMID:20550936
title: A mammalian siderophore synthesized by an enzyme with a bacterial homolog involved in enterobactin production.
findings:
- statement: BDH2 is homologous to bacterial EntA and participates in mammalian/eukaryotic siderophore synthesis.
supporting_text: The iron-binding moiety of the mammalian siderophore is 2,5-DHBA
- statement: Siderophore-depleted zebrafish embryos fail to synthesize heme.
supporting_text: zebrafish embryos fail to synthesize
- id: PMID:26929344
title: Inactivation of 3-hydroxybutyrate dehydrogenase 2 delays zebrafish erythroid maturation by conferring premature mitophagy.
findings:
- statement: Bdh2 catalyzes a rate-limiting step in eukaryotic siderophore biogenesis, and bdh2 inactivation causes heme
deficiency and delayed erythroid maturation.
supporting_text: (Bdh2), catalyzes a rate-limiting step in the biogenesis of the eukaryotic
- id: file:DANRE/bdh2/bdh2-uniprot.txt
title: UniProtKB entry Q561X9 for Danio rerio bdh2
findings:
- statement: UniProt describes separate Bdh2 roles in 4-oxo-L-proline reduction and 2,5-DHBA siderophore formation.
supporting_text: formation of 2,5-dihydroxybenzoate (2,5-DHBA)
- id: file:DANRE/bdh2/bdh2-deep-research-falcon.md
title: Falcon deep research on zebrafish bdh2 (Edison Scientific Literature)
findings:
- statement: |
Bdh2 is the rate-limiting NAD-dependent enzyme producing the endogenous catecholate siderophore 2,5-DHBA, an
iron-coordinating ligand; it is a functional homolog of bacterial EntA.
supporting_text: |
BDH2 catalyzes a **rate-limiting NAD-dependent step** in biosynthesis of **2,5-dihydroxybenzoic acid (2,5-DHBA)**, an endogenous catecholate that can coordinate iron
reference_section_type: RESULTS
- statement: |
Bdh2 enzymology is linked to catecholate siderophore chemistry through homology to bacterial EntA.
supporting_text: |
BDH2 is a functional homolog of **bacterial EntA**, linking its enzymology to catecholate siderophore chemistry
reference_section_type: RESULTS
- statement: |
The conserved BDH2 role is siderophore-dependent iron handling rather than ketone-body oxidation; BDH2 is only ~20%
identical to mitochondrial BDH1 and is dispensable for ketone-body metabolism in vivo.
supporting_text: |
is described as only ~20% identical to mitochondrial BDH1 and is considered dispensable for ketone-body metabolism in vivo in the mouse knockout study
reference_section_type: RESULTS
- statement: |
Zebrafish bdh2 knockdown causes hypochromic blood and markedly reduced o-dianisidine (heme) staining, rescued by
MO-resistant bdh2 mRNA.
supporting_text: |
morpholino knockdown causes **hypochromic blood** and **markedly reduced o-dianisidine staining**
reference_section_type: RESULTS
- statement: |
The hemoglobinization phenotype reflects impaired heme/iron handling rather than globin transcription, because
hbae1/hbae3 globin genes are expressed normally in bdh2 morphants.
supporting_text: |
globin genes (**hbae1/hbae3**) were reported as expressed normally, suggesting the phenotype reflects impaired heme/iron handling rather than globin transcription
reference_section_type: RESULTS
- statement: |
In zebrafish erythrocytes, bdh2 loss causes mitochondrial dysfunction followed by premature mitochondrial clearance
via mitophagy.
supporting_text: |
loss of bdh2 causes mitochondrial dysfunction followed by **premature mitochondrial clearance via mitophagy**
reference_section_type: RESULTS
- statement: |
Suppressing autophagy via atg7 knockdown reduces mitochondrial clearance and partially rescues hemoglobinization and
erythroid maturation (N:C ratios), placing erythroid maturation downstream of mitochondrial iron metabolism.
supporting_text: |
suppressing autophagy via **atg7** knockdown reduces mitochondrial clearance and partially rescues hemoglobinization and N:C ratios
reference_section_type: RESULTS
- statement: |
The best current (ortholog-informed) localization model places BDH2 as a cytosolic/outer-mitochondrial-membrane
enzyme enriched at mitochondria-lysosome contact sites coordinating lysosome-to-mitochondria iron transfer; not yet
directly demonstrated in zebrafish.
supporting_text: |
cytosolic/outer-mitochondrial-membrane-associated enzyme enriched at **mitochondria–lysosome contact sites**
reference_section_type: OTHER
core_functions:
- description: bdh2 enables cytosolic 4-oxoproline reductase activity, reducing 4-oxo-L-proline to cis-4-hydroxy-L-proline
as a ketoproline detoxification reaction.
molecular_function:
id: GO:0016617
label: 4-oxoproline reductase activity
directly_involved_in:
- id: GO:1990748
label: cellular detoxification
locations:
- id: GO:0005737
label: cytoplasm
supported_by:
- reference_id: file:DANRE/bdh2/bdh2-uniprot.txt
supporting_text: conversion of 4-oxo-L-proline to cis-4-hydroxy-L-proline
- reference_id: file:DANRE/bdh2/bdh2-uniprot.txt
supporting_text: detoxification mechanism for ketoprolines
- description: bdh2 also supports 2,5-DHBA-associated siderophore biosynthesis and iron delivery needed for heme metabolic
processes and erythroid maturation; no specific GO molecular-function term currently captures this siderophore-forming
activity.
molecular_function:
id: GO:0016491
label: oxidoreductase activity
directly_involved_in:
- id: GO:0019290
label: siderophore biosynthetic process
- id: GO:0042168
label: heme metabolic process
locations:
- id: GO:0005737
label: cytoplasm
supported_by:
- reference_id: file:DANRE/bdh2/bdh2-uniprot.txt
supporting_text: formation of 2,5-dihydroxybenzoate (2,5-DHBA)
- reference_id: PMID:20550936
supporting_text: The iron-binding moiety of the mammalian siderophore is 2,5-DHBA
- reference_id: PMID:26929344
supporting_text: results in heme deficiency and delays erythroid maturation
- reference_id: file:DANRE/bdh2/bdh2-deep-research-falcon.md
supporting_text: |
BDH2 catalyzes a **rate-limiting NAD-dependent step** in biosynthesis of **2,5-dihydroxybenzoic acid (2,5-DHBA)**, an endogenous catecholate that can coordinate iron