bdh2 encodes a cytosolic short-chain dehydrogenase/reductase implicated in mammalian/eukaryotic siderophore biogenesis, mitochondrial iron delivery, heme synthesis, and erythroid maturation in zebrafish. It has 4-oxoproline reductase detoxification activity and a distinct 2,5-DHBA-associated siderophore/heme role; a 3-hydroxybutyrate dehydrogenase activity is reported by similarity but appears secondary in zebrafish.
Definition: Catalysis of the NAD-dependent oxidoreduction reaction, characteristic of the short-chain dehydrogenase/reductase BDH2, that contributes to formation of 2,5-dihydroxybenzoate (2,5-DHBA), the iron-binding catecholate moiety of the mammalian siderophore, during siderophore biosynthesis.
Justification: BDH2 catalyzes a specific NAD-dependent step forming 2,5-DHBA for endogenous catecholate siderophore biosynthesis, but no existing GO molecular-function term captures this exact reaction. It is currently grounded only by the broader parent class GO:0016616 (oxidoreductase activity, acting on the CH-OH group of donors, NAD or NADP as acceptor), which does not convey the siderophore-forming specificity; a dedicated child term would.
Parent term: oxidoreductase activity, acting on the CH-OH group of donors, NAD or NADP as acceptor
Supporting Evidence:
| 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 |
| GO:1990748 cellular detoxification | IEA file:DANRE/bdh2/bdh2-uniprot.txt | NEW | Summary: NEW (proposed). The 4-oxoproline reductase activity of Bdh2 reduces 4-oxo-L-proline (a reactive ketoproline) to cis-4-hydroxy-L-proline; UniProt describes this as a detoxification mechanism for ketoprolines. Cellular detoxification is the biological process this core reductase activity serves and is not otherwise represented in the GOA set. Reason: This process grounds the detoxification role assigned to the 4-oxoproline reductase core function; it is inferred from the UniProt-described ketoproline detoxification mechanism rather than from a direct zebrafish assay. Supporting Evidence: file:DANRE/bdh2/bdh2-uniprot.txt detoxification mechanism for ketoprolines file:DANRE/bdh2/bdh2-uniprot.txt conversion of 4-oxo-L-proline to cis-4-hydroxy-L-proline |
| GO:0016616 oxidoreductase activity, acting on the CH-OH group of donors, NAD or NADP as acceptor | IEA file:DANRE/bdh2/bdh2-uniprot.txt | NEW | Summary: NEW (proposed). Beyond 4-oxoproline reductase activity, Bdh2 (a short-chain dehydrogenase/reductase) catalyzes an NAD-dependent oxidoreductase step forming 2,5-dihydroxybenzoate (2,5-DHBA), the iron-binding moiety of the mammalian catecholate siderophore. No GO term captures this exact siderophore-forming reaction, so the SDR fold and NAD dependence are grounded with the CH-OH-donor / NAD-acceptor oxidoreductase class (GO:0016616) rather than the uninformative root oxidoreductase term. Reason: The 2,5-DHBA-forming activity is a genuine NAD-dependent CH-OH-donor oxidoreductase reaction consistent with the Bdh2 SDR fold; GO:0016616 is the most specific defensible molecular-function class (more informative than the root GO:0016491 and the parent of the already-accepted GO:0016617 4-oxoproline reductase activity), inferred from UniProt and 2,5-DHBA biosynthesis evidence rather than a direct zebrafish enzymatic assay. 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 |
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