BDH1 is the mitochondrial NAD+-dependent D-beta-hydroxybutyrate dehydrogenase (EC 1.1.1.30), a short-chain dehydrogenase/reductase (SDR) family enzyme anchored to the matrix side of the mitochondrial inner membrane. It catalyses the reversible interconversion of the two principal ketone bodies, (R)-3-hydroxybutanoate + NAD+ <=> acetoacetate + NADH + H+. This single reaction serves two opposite physiological directions: it is the terminal step of hepatic ketogenesis, producing beta-hydroxybutyrate (the main circulating ketone body), and the initiating step of ketolysis in peripheral tissues (heart, brain, skeletal muscle), regenerating acetoacetate for downstream oxidation. BDH1 is a lipid-dependent enzyme that requires phosphatidylcholine as an allosteric activator for full activity, and it assembles as a homotetramer. It is highly expressed in liver and mitochondria-rich oxidative tissues, where it is central to ketone-body homeostasis and the use of ketone bodies as an alternative energy substrate during fasting, prolonged exercise, or carbohydrate restriction.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005743 mitochondrial inner membrane | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic (PAN-GO) inference that BDH1 is active in the mitochondrial inner membrane. This matches the experimentally established localization of the mammalian enzyme: BDH is an inner-membrane, lipid-requiring dehydrogenase whose active site faces the matrix. Correct and core to the protein's localization. Reason: Consistent with UniProt subcellular location and with the enzyme's known requirement for inner-membrane phosphatidylcholine. This is the primary functional location. Supporting Evidence: file:human/BDH1/BDH1-uniprot.txt Mitochondrion inner membrane PMID:8679568 enzyme with a specific requirement of phosphatidylcholine (PC) for function |
| GO:0003858 3-hydroxybutyrate dehydrogenase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic inference of the core molecular function, 3-hydroxybutyrate dehydrogenase activity (EC 1.1.1.30). This is the defining catalytic activity of BDH1 and is corroborated by direct experimental assay of the human enzyme. Reason: This is the core, evolutionarily conserved molecular function of the gene, supported by IBA, RHEA/EC mapping, and direct experimental evidence (PMID:8679568). Supporting Evidence: file:human/BDH1/BDH1-uniprot.txt Reaction=(R)-3-hydroxybutanoate + NAD(+) = acetoacetate + NADH + H(+) |
| GO:0003858 3-hydroxybutyrate dehydrogenase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Automated (RHEA:20521 / EC:1.1.1.30) assignment of 3-hydroxybutyrate dehydrogenase activity. This duplicates the IBA and IDA annotations of the same core function and maps to the exact catalytic reaction curated in UniProt. Reason: Correct core molecular-function assignment derived from the RHEA/EC reaction; duplicate of the experimentally supported activity, which is acceptable. Supporting Evidence: file:human/BDH1/BDH1-uniprot.txt Reaction=(R)-3-hydroxybutanoate + NAD(+) = acetoacetate + NADH + H(+) |
| GO:0005743 mitochondrial inner membrane | IEA GO_REF:0000044 | ACCEPT | Summary: Automated UniProt Subcellular Location mapping (SL-0168) to mitochondrial inner membrane, consistent with the curated location and with the enzyme's inner-membrane lipid requirement. Reason: Matches curated UniProt subcellular location and the IBA/ISS inner-membrane annotations. Supporting Evidence: file:human/BDH1/BDH1-uniprot.txt Mitochondrion inner membrane |
| GO:0005759 mitochondrial matrix | IEA GO_REF:0000044 | ACCEPT | Summary: Automated UniProt Subcellular Location mapping (SL-0170) to mitochondrial matrix. BDH1 is an inner-membrane protein whose catalytic domain faces the matrix (see the more precise GO:0099617 matrix side of mitochondrial inner membrane annotation), and UniProt records both inner membrane and matrix locations. Reason: Consistent with UniProt (Mitochondrion matrix) and with the matrix-facing orientation of the active site; a valid, if less precise, location statement. Supporting Evidence: file:human/BDH1/BDH1-uniprot.txt Mitochondrion inner membrane |
| GO:0016616 oxidoreductase activity, acting on the CH-OH group of donors, NAD or NADP as acceptor | IEA GO_REF:0000117 | MARK AS OVER ANNOTATED | Summary: ARBA machine-learning IEA assigning the broad parent activity "oxidoreductase acting on the CH-OH group of donors, NAD or NADP as acceptor". This is a direct ancestor of the specific, experimentally supported GO:0003858 3-hydroxybutyrate dehydrogenase activity. Reason: Not incorrect, but redundant with and far less informative than the specific EC 1.1.1.30 activity (GO:0003858) already annotated by IBA/IDA/RHEA. The specific term should be used to represent the molecular function. Supporting Evidence: file:human/BDH1/BDH1-uniprot.txt Reaction=(R)-3-hydroxybutanoate + NAD(+) = acetoacetate + NADH + H(+) |
| GO:0042181 ketone biosynthetic process | IEA GO_REF:0000107 | MODIFY | Summary: Ensembl-Compara orthology IEA (from mouse Bdh1) placing BDH1 in "ketone biosynthetic process". BDH1 acts specifically on the ketone bodies beta-hydroxybutyrate/acetoacetate and catalyses the terminal step of ketogenesis, so the ketone-body-specific process term is more accurate than the general "ketone" term. Reason: The essence is correct (biosynthetic role) but the term is more general than warranted. BDH1 produces the ketone body beta-hydroxybutyrate in the final step of ketogenesis; the ketone-body-specific term better captures this. Proposed replacements: ketone body biosynthetic process Supporting Evidence: file:human/BDH1/BDH1-uniprot.txt Reaction=(R)-3-hydroxybutanoate + NAD(+) = acetoacetate + NADH + H(+) Reactome:R-HSA-73912 catalyzes the reversible reaction of acetoacetate with NADH + H+ to form |
| GO:0042182 ketone catabolic process | IEA GO_REF:0000107 | MODIFY | Summary: Ensembl-Compara orthology IEA (from mouse Bdh1) placing BDH1 in "ketone catabolic process". In peripheral tissues BDH1 oxidizes beta-hydroxybutyrate to acetoacetate as the first step of ketolysis (ketone-body utilization), so the ketone-body-specific catabolic term is more accurate. Reason: The essence is correct (catabolic/utilization role) but the term is more general than warranted. BDH1 acts specifically on the ketone body beta-hydroxybutyrate; the ketone-body-specific term better captures the ketolysis-initiating step. Proposed replacements: ketone body catabolic process Supporting Evidence: Reactome:R-HSA-73920 catalyzes the reversible reaction of D-beta hydroxybutyrate and NAD+ to form |
| GO:0005743 mitochondrial inner membrane | ISS GO_REF:0000024 | ACCEPT | Summary: ISS location (from rat ortholog Q02337) to mitochondrial inner membrane, matching the experimentally established localization of the mammalian enzyme. Reason: Consistent with UniProt and the IBA/IEA inner-membrane annotations; core location. Supporting Evidence: file:human/BDH1/BDH1-uniprot.txt Mitochondrion inner membrane |
| GO:0005759 mitochondrial matrix | ISS GO_REF:0000024 | ACCEPT | Summary: ISS location (from rat ortholog Q02337) to mitochondrial matrix, consistent with the matrix-facing orientation of the inner-membrane-anchored enzyme. Reason: Consistent with UniProt (Mitochondrion matrix) and with the matrix-facing active site; valid though less precise than GO:0099617. Supporting Evidence: file:human/BDH1/BDH1-uniprot.txt Mitochondrion inner membrane |
| GO:0005739 mitochondrion | HTP PMID:34800366 Quantitative high-confidence human mitochondrial proteome an... | ACCEPT | Summary: High-throughput identification of BDH1 in the high-confidence human mitochondrial proteome (MitoCoP). Correct but broad organelle-level localization. Reason: Confirmed mitochondrial protein by a high-confidence proteomics resource; broader than the inner-membrane/matrix annotations but not incorrect. Non-core relative to the more specific inner-membrane location. Supporting Evidence: PMID:34800366 1,134 protein-coding genes |
| GO:0099617 matrix side of mitochondrial inner membrane | ISS GO_REF:0000024 | ACCEPT | Summary: ISS location (from rat ortholog Q02337) to the matrix side of the mitochondrial inner membrane. This is the most precise and biologically informative location: BDH1 is anchored to the inner membrane with its catalytic/NAD-binding domain facing the matrix. Reason: Most precise localization, consistent with the inner-membrane anchoring and matrix-facing active site of the lipid-dependent enzyme. Represents the core location. Supporting Evidence: file:human/BDH1/BDH1-uniprot.txt Mitochondrion inner membrane PMID:8679568 enzyme with a specific requirement of phosphatidylcholine (PC) for function |
| GO:0005759 mitochondrial matrix | TAS Reactome:R-HSA-73912 | ACCEPT | Summary: Reactome TAS location (matrix) associated with the ketogenesis-direction reaction (acetoacetate + NADH -> beta-hydroxybutyrate + NAD+). The location statement is consistent with the enzyme's matrix-facing activity. Reason: Consistent with the curated matrix location; the associated Reactome reaction is the synthesis direction of the BDH1-catalysed interconversion. Supporting Evidence: Reactome:R-HSA-73912 catalyzes the reversible reaction of acetoacetate with NADH + H+ to form |
| GO:0005759 mitochondrial matrix | TAS Reactome:R-HSA-73920 | ACCEPT | Summary: Reactome TAS location (matrix) associated with the ketolysis-direction reaction (beta-hydroxybutyrate + NAD+ -> acetoacetate + NADH). Consistent with the matrix-facing activity of the enzyme. Reason: Consistent with the curated matrix location; the associated Reactome reaction is the utilization direction of the BDH1-catalysed interconversion. Supporting Evidence: Reactome:R-HSA-73920 catalyzes the reversible reaction of D-beta hydroxybutyrate and NAD+ to form |
| GO:0005759 mitochondrial matrix | TAS Reactome:R-HSA-9838035 | ACCEPT | Summary: Reactome TAS location (matrix) arising from the generic reaction "CLPXP binds mitochondrial matrix proteins", in which BDH1 is one of many matrix proteins engaged by the CLPXP quality- control protease. The location assignment is correct, but this reflects BDH1 being a protease substrate, not a BDH1-specific function. Reason: The mitochondrial matrix localization is valid and consistent with the other matrix annotations. It is noted that it is derived from generic CLPXP protein-degradation biology rather than BDH1's own catalytic function, so it is a non-core (provenance) location. Supporting Evidence: Reactome:R-HSA-9838035 interacts with more than 200 mitochondrial proteins |
| GO:0005759 mitochondrial matrix | TAS Reactome:R-HSA-9838289 | ACCEPT | Summary: Reactome TAS location (matrix) arising from the generic reaction "CLPXP degrades mitochondrial matrix proteins", where BDH1 is a substrate of the CLPXP protease. The location is correct but reflects generic proteostasis, not a BDH1-specific role. Reason: Valid matrix localization, consistent with the other matrix annotations; it is derived from CLPXP-mediated protein degradation biology rather than BDH1's catalytic function, hence a non-core (provenance) location. Supporting Evidence: Reactome:R-HSA-9838289 binds and degrades |
| GO:0003858 3-hydroxybutyrate dehydrogenase activity | IDA PMID:8679568 Wild type and mutant human heart (R)-3-hydroxybutyrate dehyd... | ACCEPT | Summary: Direct experimental assay of the human enzyme: mature human heart BDH expressed in Sf9 insect cells is catalytically active with Km values for NAD+ and (R)-3-hydroxybutyrate similar to native mammalian BDH, and shows the characteristic phosphatidylcholine requirement. This is the strongest evidence for the core molecular function. Reason: Direct experimental (IDA) demonstration of 3-hydroxybutyrate dehydrogenase activity for the human protein; the defining core function of BDH1. Supporting Evidence: PMID:8679568 The K(m)s for NAD+ and (R)-3-hydroxybutyrate PMID:8679568 enzyme with a specific requirement of phosphatidylcholine (PC) for function |
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Download this section (compressed HTML)Q: Do the two Reactome directions (synthesis vs utilization) reflect genuinely tissue-directional physiology of the same BDH1 enzyme (liver ketogenesis vs peripheral ketolysis), or does BDH1 equilibrium in vivo depend chiefly on the mitochondrial NAD+/NADH ratio in each tissue?
Q: Is BDH1's phosphatidylcholine dependence rate-limiting for ketone-body flux under physiological conditions, or is it primarily a structural/regulatory feature of the inner-membrane enzyme?
Experiment: Tissue-specific stable-isotope tracing of beta-hydroxybutyrate/acetoacetate flux in liver versus heart/brain with BDH1 depletion to test the directional (ketogenic vs ketolytic) roles.
Hypothesis: BDH1 controls net directionality of ketone-body interconversion primarily through the local mitochondrial NAD+/NADH ratio rather than intrinsic tissue-specific enzyme differences.
Type: metabolic flux analysis
Experiment: Reconstitution of purified human BDH1 into liposomes of varying phosphatidylcholine content to quantify the dependence of Vmax/Km on membrane PC.
Hypothesis: Phosphatidylcholine is an obligatory allosteric activator that modulates NAD(H) binding affinity and thus catalytic efficiency of BDH1.
Type: enzyme kinetics / reconstitution
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