id: Q02338
gene_symbol: BDH1
product_type: PROTEIN
status: INITIALIZED
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: >-
  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.
existing_annotations:
- term:
    id: GO:0005743
    label: mitochondrial inner membrane
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: is_active_in
  review:
    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.
    action: ACCEPT
    reason: >-
      Consistent with UniProt subcellular location and with the enzyme's known requirement for
      inner-membrane phosphatidylcholine. This is the primary functional location.
    supported_by:
    - reference_id: file:human/BDH1/BDH1-uniprot.txt
      supporting_text: Mitochondrion inner membrane
    - reference_id: PMID:8679568
      supporting_text: enzyme with a specific requirement of phosphatidylcholine (PC) for function
- term:
    id: GO:0003858
    label: 3-hydroxybutyrate dehydrogenase activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: enables
  review:
    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.
    action: ACCEPT
    reason: >-
      This is the core, evolutionarily conserved molecular function of the gene, supported by IBA,
      RHEA/EC mapping, and direct experimental evidence (PMID:8679568).
    supported_by:
    - reference_id: file:human/BDH1/BDH1-uniprot.txt
      supporting_text: Reaction=(R)-3-hydroxybutanoate + NAD(+) = acetoacetate + NADH + H(+)
- term:
    id: GO:0003858
    label: 3-hydroxybutyrate dehydrogenase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: enables
  review:
    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.
    action: ACCEPT
    reason: >-
      Correct core molecular-function assignment derived from the RHEA/EC reaction; duplicate of the
      experimentally supported activity, which is acceptable.
    supported_by:
    - reference_id: file:human/BDH1/BDH1-uniprot.txt
      supporting_text: Reaction=(R)-3-hydroxybutanoate + NAD(+) = acetoacetate + NADH + H(+)
- term:
    id: GO:0005743
    label: mitochondrial inner membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    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.
    action: ACCEPT
    reason: Matches curated UniProt subcellular location and the IBA/ISS inner-membrane annotations.
    supported_by:
    - reference_id: file:human/BDH1/BDH1-uniprot.txt
      supporting_text: Mitochondrion inner membrane
- term:
    id: GO:0005759
    label: mitochondrial matrix
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    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.
    action: ACCEPT
    reason: >-
      Consistent with UniProt (Mitochondrion matrix) and with the matrix-facing orientation of the
      active site; a valid, if less precise, location statement.
    supported_by:
    - reference_id: file:human/BDH1/BDH1-uniprot.txt
      supporting_text: Mitochondrion inner membrane
- term:
    id: GO:0016616
    label: oxidoreductase activity, acting on the CH-OH group of donors, NAD or NADP
      as acceptor
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  qualifier: enables
  review:
    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.
    action: MARK_AS_OVER_ANNOTATED
    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.
    supported_by:
    - reference_id: file:human/BDH1/BDH1-uniprot.txt
      supporting_text: Reaction=(R)-3-hydroxybutanoate + NAD(+) = acetoacetate + NADH + H(+)
- term:
    id: GO:0042181
    label: ketone biosynthetic process
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    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.
    action: MODIFY
    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_replacement_terms:
    - id: GO:0046951
      label: ketone body biosynthetic process
    supported_by:
    - reference_id: file:human/BDH1/BDH1-uniprot.txt
      supporting_text: Reaction=(R)-3-hydroxybutanoate + NAD(+) = acetoacetate + NADH + H(+)
    - reference_id: Reactome:R-HSA-73912
      supporting_text: catalyzes the reversible reaction of acetoacetate with NADH + H+ to form
- term:
    id: GO:0042182
    label: ketone catabolic process
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    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.
    action: MODIFY
    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_replacement_terms:
    - id: GO:0046952
      label: ketone body catabolic process
    supported_by:
    - reference_id: Reactome:R-HSA-73920
      supporting_text: catalyzes the reversible reaction of D-beta hydroxybutyrate and NAD+ to form
- term:
    id: GO:0005743
    label: mitochondrial inner membrane
  evidence_type: ISS
  original_reference_id: GO_REF:0000024
  qualifier: located_in
  review:
    summary: >-
      ISS location (from rat ortholog Q02337) to mitochondrial inner membrane, matching the
      experimentally established localization of the mammalian enzyme.
    action: ACCEPT
    reason: Consistent with UniProt and the IBA/IEA inner-membrane annotations; core location.
    supported_by:
    - reference_id: file:human/BDH1/BDH1-uniprot.txt
      supporting_text: Mitochondrion inner membrane
- term:
    id: GO:0005759
    label: mitochondrial matrix
  evidence_type: ISS
  original_reference_id: GO_REF:0000024
  qualifier: located_in
  review:
    summary: >-
      ISS location (from rat ortholog Q02337) to mitochondrial matrix, consistent with the
      matrix-facing orientation of the inner-membrane-anchored enzyme.
    action: ACCEPT
    reason: >-
      Consistent with UniProt (Mitochondrion matrix) and with the matrix-facing active site;
      valid though less precise than GO:0099617.
    supported_by:
    - reference_id: file:human/BDH1/BDH1-uniprot.txt
      supporting_text: Mitochondrion inner membrane
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: HTP
  original_reference_id: PMID:34800366
  qualifier: located_in
  review:
    summary: >-
      High-throughput identification of BDH1 in the high-confidence human mitochondrial proteome
      (MitoCoP). Correct but broad organelle-level localization.
    action: ACCEPT
    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.
    supported_by:
    - reference_id: PMID:34800366
      supporting_text: '1,134 protein-coding genes'
- term:
    id: GO:0099617
    label: matrix side of mitochondrial inner membrane
  evidence_type: ISS
  original_reference_id: GO_REF:0000024
  qualifier: located_in
  review:
    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.
    action: ACCEPT
    reason: >-
      Most precise localization, consistent with the inner-membrane anchoring and matrix-facing
      active site of the lipid-dependent enzyme. Represents the core location.
    supported_by:
    - reference_id: file:human/BDH1/BDH1-uniprot.txt
      supporting_text: Mitochondrion inner membrane
    - reference_id: PMID:8679568
      supporting_text: enzyme with a specific requirement of phosphatidylcholine (PC) for function
- term:
    id: GO:0005759
    label: mitochondrial matrix
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-73912
  qualifier: located_in
  review:
    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.
    action: ACCEPT
    reason: >-
      Consistent with the curated matrix location; the associated Reactome reaction is the
      synthesis direction of the BDH1-catalysed interconversion.
    supported_by:
    - reference_id: Reactome:R-HSA-73912
      supporting_text: catalyzes the reversible reaction of acetoacetate with NADH + H+ to form
- term:
    id: GO:0005759
    label: mitochondrial matrix
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-73920
  qualifier: located_in
  review:
    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.
    action: ACCEPT
    reason: >-
      Consistent with the curated matrix location; the associated Reactome reaction is the
      utilization direction of the BDH1-catalysed interconversion.
    supported_by:
    - reference_id: Reactome:R-HSA-73920
      supporting_text: catalyzes the reversible reaction of D-beta hydroxybutyrate and NAD+ to form
- term:
    id: GO:0005759
    label: mitochondrial matrix
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9838035
  qualifier: located_in
  review:
    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.
    action: ACCEPT
    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.
    supported_by:
    - reference_id: Reactome:R-HSA-9838035
      supporting_text: interacts with more than 200 mitochondrial proteins
- term:
    id: GO:0005759
    label: mitochondrial matrix
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9838289
  qualifier: located_in
  review:
    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.
    action: ACCEPT
    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.
    supported_by:
    - reference_id: Reactome:R-HSA-9838289
      supporting_text: binds and degrades
- term:
    id: GO:0003858
    label: 3-hydroxybutyrate dehydrogenase activity
  evidence_type: IDA
  original_reference_id: PMID:8679568
  qualifier: enables
  review:
    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.
    action: ACCEPT
    reason: >-
      Direct experimental (IDA) demonstration of 3-hydroxybutyrate dehydrogenase activity for the
      human protein; the defining core function of BDH1.
    supported_by:
    - reference_id: PMID:8679568
      supporting_text: The K(m)s for NAD+ and (R)-3-hydroxybutyrate
    - reference_id: PMID:8679568
      supporting_text: enzyme with a specific requirement of phosphatidylcholine (PC) for function
core_functions:
- description: >-
    NAD+-dependent oxidation of (R)-3-hydroxybutyrate to acetoacetate (and the reverse reduction),
    the reversible dehydrogenase reaction (EC 1.1.1.30) that interconverts the two ketone bodies at
    the matrix side of the mitochondrial inner membrane. This activity requires phosphatidylcholine
    as an allosteric activator and is the enzymatic basis of both ketogenesis and ketolysis.
  molecular_function:
    id: GO:0003858
    label: 3-hydroxybutyrate dehydrogenase activity
  directly_involved_in:
  - id: GO:0046951
    label: ketone body biosynthetic process
  - id: GO:0046952
    label: ketone body catabolic process
  locations:
  - id: GO:0099617
    label: matrix side of mitochondrial inner membrane
  - id: GO:0005743
    label: mitochondrial inner membrane
  substrates:
  - id: CHEBI:10983
    label: (R)-3-hydroxybutyrate
  - id: CHEBI:13705
    label: acetoacetate
  supported_by:
  - reference_id: PMID:8679568
    supporting_text: The K(m)s for NAD+ and (R)-3-hydroxybutyrate
  - reference_id: file:human/BDH1/BDH1-uniprot.txt
    supporting_text: Reaction=(R)-3-hydroxybutanoate + NAD(+) = acetoacetate + NADH + H(+)
  - reference_id: Reactome:R-HSA-73920
    supporting_text: catalyzes the reversible reaction of D-beta hydroxybutyrate and NAD+ to form
proposed_new_terms: []
suggested_questions:
- question: >-
    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?
- question: >-
    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?
suggested_experiments:
- description: >-
    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.
  experiment_type: metabolic flux analysis
  hypothesis: >-
    BDH1 controls net directionality of ketone-body interconversion primarily through the local
    mitochondrial NAD+/NADH ratio rather than intrinsic tissue-specific enzyme differences.
- description: >-
    Reconstitution of purified human BDH1 into liposomes of varying phosphatidylcholine content to
    quantify the dependence of Vmax/Km on membrane PC.
  experiment_type: enzyme kinetics / reconstitution
  hypothesis: >-
    Phosphatidylcholine is an obligatory allosteric activator that modulates NAD(H) binding affinity
    and thus catalytic efficiency of BDH1.
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:0000107
  title: Automatic transfer of experimentally verified manual GO annotation data to
    orthologs using Ensembl Compara
  findings: []
- id: GO_REF:0000117
  title: Electronic Gene Ontology annotations created by ARBA machine learning models
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:34800366
  title: Quantitative high-confidence human mitochondrial proteome and its dynamics
    in cellular context.
  findings:
  - statement: >-
      BDH1 is a member of the high-confidence human mitochondrial proteome (MitoCoP, 1,134
      protein-coding genes), confirming its mitochondrial localization.
    reference_section_type: RESULTS
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified proteomics resource; supports the HTP mitochondrion localization for BDH1.
- id: PMID:8679568
  title: Wild type and mutant human heart (R)-3-hydroxybutyrate dehydrogenase expressed
    in insect cells.
  findings:
  - statement: >-
      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 enzyme, and requires
      phosphatidylcholine as an allosteric activator.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Directly establishes the human enzyme's 3-hydroxybutyrate dehydrogenase activity and PC
      requirement; supports the IDA for GO:0003858. Cached record is abstract-only.
- id: Reactome:R-HSA-73912
  title: acetoacetic acid + NADH + H+ <=> beta-hydroxybutyrate + NAD+
  findings:
  - statement: >-
      BDH1 tetramer catalyses the ketogenesis-direction reaction, reducing acetoacetate to
      beta-hydroxybutyrate with NADH.
    reference_section_type: OTHER
- id: Reactome:R-HSA-73920
  title: D-beta hydroxybutyrate+NAD+ <=> acetoacetate+NADH+H+
  findings:
  - statement: >-
      BDH1 tetramer catalyses the ketolysis-direction reaction, oxidising beta-hydroxybutyrate to
      acetoacetate with NAD+.
    reference_section_type: OTHER
- id: Reactome:R-HSA-9838035
  title: CLPXP binds mitochondrial matrix proteins
  findings:
  - statement: >-
      BDH1 is engaged as one of many mitochondrial matrix substrates of the CLPXP quality-control
      protease; supports matrix localization but not a BDH1-specific function.
    reference_section_type: OTHER
- id: Reactome:R-HSA-9838289
  title: CLPXP degrades mitochondrial matrix proteins
  findings:
  - statement: >-
      BDH1 is a substrate degraded by the CLPXP protease in the mitochondrial matrix; supports
      matrix localization as part of generic proteostasis.
    reference_section_type: OTHER