id: P11310
gene_symbol: ACADM
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: >-
  ACADM (MCAD, medium-chain specific acyl-CoA dehydrogenase) is a mitochondrial matrix
  flavoenzyme that catalyzes the first, committed step of each cycle of mitochondrial fatty
  acid beta-oxidation for medium-chain acyl-CoA esters. It performs the FAD-dependent,
  stereospecific alpha,beta-dehydrogenation of a saturated acyl-CoA to the corresponding
  trans-2-enoyl-CoA, transferring electrons to the electron-transfer flavoprotein (ETF) and,
  via ETF-ubiquinone oxidoreductase, into the respiratory chain (EC 1.3.8.7). MCAD has broad
  medium-chain substrate preference with an optimum around hexanoyl-/octanoyl-CoA (C6-C8),
  extending across roughly C4-C12 and with weaker activity toward longer chains. The mature
  enzyme is a soluble homotetramer, each subunit carrying one non-covalently bound FAD, with a
  catalytic glutamate that abstracts the substrate alpha-proton. MCAD is expressed
  ubiquitously, highest in heart and muscle, and supports energy production from fat during
  fasting and increased energy demand. Loss-of-function variants in ACADM cause MCAD deficiency
  (ACADMD), the most common inherited fatty acid oxidation disorder, in which the prevalent
  c.985A>G (K304E) and other missense changes act largely by protein misfolding and impaired
  tetramer assembly, producing hypoketotic hypoglycemia during catabolic stress.
alternative_products:
- name: '1'
  id: P11310-1
- name: '2'
  id: P11310-2
  sequence_note: VSP_038420
existing_annotations:
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: is_active_in
  review:
    summary: >-
      Phylogenetically inferred cytoplasmic localization. MCAD is in fact a mitochondrial matrix
      protein; "cytoplasm" is an over-general parent that does not capture the precise
      compartment. It is not strictly wrong (mitochondrion is within the cytoplasm) but is
      uninformative relative to the well-supported mitochondrial matrix localization.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      The precise and experimentally supported location is the mitochondrial matrix
      (GO:0005759). The IBA "cytoplasm" call is an over-general placeholder.
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: is_active_in
  review:
    summary: >-
      Phylogenetically inferred mitochondrial localization, consistent with all experimental
      evidence. Correct but less precise than the mitochondrial matrix annotation.
    action: KEEP_AS_NON_CORE
    reason: >-
      Mitochondrial localization is well established; the more specific term (mitochondrial
      matrix) is the core location annotation.
    supported_by:
    - reference_id: PMID:1902818
      supporting_text: "Demonstration of intra-mitochondrial mature MCAD indistinguishable in size (42.5-kDa) from control MCAD"
- term:
    id: GO:0051793
    label: medium-chain fatty acid catabolic process
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: >-
      Phylogenetically inferred role in medium-chain fatty acid catabolism, directly matching
      MCAD's biochemical function. This is a core process for MCAD and is also independently
      supported by direct experimental annotations (PMID:1970566).
    action: ACCEPT
    reason: >-
      MCAD catabolizes medium-chain fatty acids via beta-oxidation; this term accurately
      captures its core biological process.
    supported_by:
    - reference_id: PMID:19224950
      supporting_text: "MCAD is a member of the acyl-CoA dehydrogenase (ACAD) family of flavoproteins, which catalyzes the first step of the mitochondrial β-oxidation of medium-chain fatty acids"
- term:
    id: GO:0033539
    label: fatty acid beta-oxidation using acyl-CoA dehydrogenase
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: >-
      Phylogenetically inferred participation in the acyl-CoA-dehydrogenase-dependent step of
      beta-oxidation. This is the defining process for ACAD-family enzymes and is the most
      precise process term for MCAD's role, strongly supported by direct experimental annotations.
    action: ACCEPT
    reason: >-
      MCAD performs the acyl-CoA dehydrogenase step of beta-oxidation; this is a core process
      annotation.
    supported_by:
    - reference_id: PMID:19224950
      supporting_text: "MCAD is a member of the acyl-CoA dehydrogenase (ACAD) family of flavoproteins, which catalyzes the first step of the mitochondrial β-oxidation of medium-chain fatty acids"
- term:
    id: GO:0070991
    label: medium-chain fatty acyl-CoA dehydrogenase activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: enables
  review:
    summary: >-
      Phylogenetically inferred medium-chain acyl-CoA dehydrogenase activity. This is MCAD's
      defining molecular function and is independently and directly supported by enzyme
      characterization (PMID:8823175, PMID:21237683, PMID:1970566). The IBA call is at the
      correct level of specificity.
    action: ACCEPT
    reason: >-
      This is the core molecular function of MCAD, corroborated by multiple direct biochemical
      studies establishing optimal activity toward medium-chain (C6-C8) acyl-CoA substrates.
    supported_by:
    - reference_id: PMID:8823175
      supporting_text: "medium chain acyl-CoA dehydrogenase (MCADH)"
- term:
    id: GO:0003995
    label: acyl-CoA dehydrogenase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: enables
  review:
    summary: >-
      InterPro/automated annotation of the general acyl-CoA dehydrogenase activity. Correct but
      a broad parent of the specific medium-chain activity (GO:0070991). Retained as accurate
      but non-core because the specific child term is the informative annotation.
    action: KEEP_AS_NON_CORE
    reason: >-
      MCAD is an acyl-CoA dehydrogenase; this general term is correct but subsumed by the
      more specific medium-chain activity that captures MCAD's actual function.
    supported_by:
    - reference_id: PMID:1970566
      supporting_text: "human medium chain acyl-CoA dehydrogenase (MCADH)"
- term:
    id: GO:0004466
    label: long-chain fatty acyl-CoA dehydrogenase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000116
  qualifier: enables
  review:
    summary: >-
      Rhea-based automated annotation derived from MCAD being able to turn over C14 (and C16)
      acyl-CoA substrates in vitro. While MCAD can act on these longer chains, its primary,
      defining specificity is medium-chain; the dedicated long-chain enzymes are ACADVL (VLCAD)
      and ACAD9. Annotating MCAD with a long-chain-specific molecular function overstates its
      specificity.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      MCAD's catalytic optimum is C6-C8 with high KM/low efficiency for long chains; the
      long-chain-specific MF term mischaracterizes the enzyme. The accurate MF term is
      medium-chain fatty acyl-CoA dehydrogenase activity (GO:0070991).
    supported_by:
    - reference_id: PMID:8823175
      supporting_text: "native MCADH (hexanoyl/octanoyl-CoA)"
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: located_in
  review:
    summary: >-
      Automated mitochondrial localization, consistent with experimental data. Correct but less
      precise than mitochondrial matrix.
    action: KEEP_AS_NON_CORE
    reason: >-
      Mitochondrial localization is correct; matrix is the precise core location.
    supported_by:
    - reference_id: PMID:1902818
      supporting_text: "Demonstration of intra-mitochondrial mature MCAD indistinguishable in size (42.5-kDa) from control MCAD"
- term:
    id: GO:0005759
    label: mitochondrial matrix
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: >-
      Automated subcellular-location-based annotation to mitochondrial matrix, matching the
      experimentally supported localization of this soluble matrix flavoenzyme. This is the
      core location annotation for MCAD.
    action: ACCEPT
    reason: >-
      MCAD is a soluble mitochondrial matrix protein; matrix is the correct, precise compartment.
- term:
    id: GO:0006635
    label: fatty acid beta-oxidation
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: involved_in
  review:
    summary: >-
      InterPro-based annotation to fatty acid beta-oxidation, the pathway MCAD initiates. This
      is a core biological process for MCAD and is also directly supported by experimental
      annotation (PMID:2393404).
    action: ACCEPT
    reason: >-
      MCAD catalyzes the first step of mitochondrial fatty acid beta-oxidation; this is a core
      process annotation.
    supported_by:
    - reference_id: PMID:19224950
      supporting_text: "catalyzes the first step of the mitochondrial β-oxidation of medium-chain fatty acids"
- term:
    id: GO:0016627
    label: oxidoreductase activity, acting on the CH-CH group of donors
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: >-
      InterPro-based annotation of the general oxidoreductase class. MCAD's reaction oxidizes the
      C2-C3 (alpha-beta) CH-CH bond, so this term is accurate but is a broad parent of the
      specific acyl-CoA dehydrogenase activity.
    action: KEEP_AS_NON_CORE
    reason: >-
      Correct intermediate-level term; subsumed by the specific medium-chain acyl-CoA
      dehydrogenase activity that is the informative MF annotation.
    supported_by:
    - reference_id: PMID:1970566
      supporting_text: "Glu376 plays an important role in the initial step of dehydrogenation catalysis"
- term:
    id: GO:0016937
    label: short-chain fatty acyl-CoA dehydrogenase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000116
  qualifier: enables
  review:
    summary: >-
      Rhea-based automated annotation from MCAD's ability to dehydrogenate pentanoyl-CoA (C5).
      MCAD has only weak activity at the short-chain end (e.g. butyryl-CoA KM ~175 uM, the
      poorest of its substrates); short-chain specificity belongs to ACADS (SCAD). Annotating
      MCAD with a short-chain-specific MF overstates its specificity.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      MCAD's defining specificity is medium-chain; short-chain activity is marginal and is the
      province of SCAD. The accurate MF term is GO:0070991.
    supported_by:
    - reference_id: PMID:8823175
      supporting_text: "native MCADH (hexanoyl/octanoyl-CoA)"
- term:
    id: GO:0050660
    label: flavin adenine dinucleotide binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: >-
      InterPro-based annotation of FAD binding. MCAD is a flavoprotein carrying one
      non-covalently bound FAD per subunit, essential for catalysis; the wild-type enzyme is
      yellow due to its stoichiometric FAD content. This is a correct and supported cofactor-binding
      function.
    action: ACCEPT
    reason: >-
      FAD binding is experimentally established and required for MCAD catalysis.
    supported_by:
    - reference_id: PMID:1970566
      supporting_text: "The wild-type enzyme is a yellow protein due to the content of stoichiometric FAD"
- term:
    id: GO:0070991
    label: medium-chain fatty acyl-CoA dehydrogenase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: enables
  review:
    summary: >-
      Automated annotation of the core medium-chain acyl-CoA dehydrogenase activity, fully
      consistent with the direct experimental (EXP/IDA) annotations. Correct and at the right
      specificity.
    action: ACCEPT
    reason: >-
      Core molecular function of MCAD, redundantly and directly supported.
- term:
    id: GO:0005978
    label: glycogen biosynthetic process
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: >-
      Electronic annotation transferred from a mouse ortholog via Ensembl Compara. There is no
      mechanistic connection between MCAD (a fatty acid beta-oxidation enzyme) and glycogen
      biosynthesis. Any phenotypic link in mouse would be indirect (altered fuel utilization),
      not a direct role of MCAD in glycogen synthesis.
    action: REMOVE
    reason: >-
      MCAD is a mitochondrial FAO dehydrogenase; it does not participate in glycogen
      biosynthesis. This is a spurious ortholog-transfer over-propagation.
- term:
    id: GO:0006111
    label: regulation of gluconeogenesis
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: >-
      Electronic annotation transferred from a mouse ortholog. Any influence of MCAD on
      gluconeogenesis is indirect, mediated by the metabolic consequences of fatty acid oxidation
      (acetyl-CoA supply, NADH/redox, energy state) rather than a direct regulatory function of
      the protein. Not a core function and biologically over-interpreted as a direct role.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      The link to gluconeogenesis is an indirect downstream metabolic consequence of FAO, not a
      direct regulatory activity of MCAD.
- term:
    id: GO:0019254
    label: carnitine metabolic process, CoA-linked
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: >-
      Electronic ortholog-transfer annotation related to carnitine handling. As discussed for the
      experimental carnitine annotations below, MCAD's connection to carnitine metabolism is
      indirect (acylcarnitine accumulation/clearance in MCAD deficiency), not a direct enzymatic
      role in carnitine metabolism.
    action: KEEP_AS_NON_CORE
    reason: >-
      Indirect/secondary association via acylcarnitine handling; not a core function.
- term:
    id: GO:0033539
    label: fatty acid beta-oxidation using acyl-CoA dehydrogenase
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: involved_in
  review:
    summary: >-
      Automated annotation duplicating the core acyl-CoA-dehydrogenase-dependent beta-oxidation
      process, consistent with the IBA and direct experimental annotations.
    action: ACCEPT
    reason: >-
      Core process for MCAD, redundantly supported.
    supported_by:
    - reference_id: PMID:19224950
      supporting_text: "catalyzes the first step of the mitochondrial β-oxidation of medium-chain fatty acids"
- term:
    id: GO:0051791
    label: medium-chain fatty acid metabolic process
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: involved_in
  review:
    summary: >-
      Automated annotation to medium-chain fatty acid metabolism. Accurate for MCAD; the
      catabolic child term (GO:0051793) is more precise but this parent is also correct and
      directly supported (PMID:1970566).
    action: ACCEPT
    reason: >-
      MCAD acts on medium-chain fatty acids; this process term is correct.
    supported_by:
    - reference_id: PMID:19224950
      supporting_text: "catalyzes the first step of the mitochondrial β-oxidation of medium-chain fatty acids"
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: IDA
  original_reference_id: GO_REF:0000052
  qualifier: located_in
  review:
    summary: >-
      Immunofluorescence-based (HPA) mitochondrial localization. Consistent with all other
      evidence; correct but less specific than mitochondrial matrix.
    action: KEEP_AS_NON_CORE
    reason: >-
      Mitochondrial localization is correct; matrix is the precise core compartment.
    supported_by:
    - reference_id: PMID:1902818
      supporting_text: "Demonstration of intra-mitochondrial mature MCAD indistinguishable in size (42.5-kDa) from control MCAD"
- term:
    id: GO:0070991
    label: medium-chain fatty acyl-CoA dehydrogenase activity
  evidence_type: EXP
  original_reference_id: PMID:21237683
  qualifier: enables
  review:
    summary: >-
      Direct experimental annotation of MCAD's core medium-chain acyl-CoA dehydrogenase activity.
      He et al. characterized the human ACAD family including MCAD in cerebellum, confirming MCAD's
      activity. This is the strongest type of support for the defining molecular function.
    action: ACCEPT
    reason: >-
      Experimentally supported core molecular function of MCAD.
- term:
    id: GO:0070991
    label: medium-chain fatty acyl-CoA dehydrogenase activity
  evidence_type: EXP
  original_reference_id: PMID:8823175
  qualifier: enables
  review:
    summary: >-
      Direct experimental annotation from detailed kinetic/substrate-specificity characterization
      of recombinant human MCAD, establishing the medium-chain optimum (hexanoyl/octanoyl-CoA).
      Core molecular function.
    action: ACCEPT
    reason: >-
      Experimentally supported core molecular function; the study defines MCAD's chain-length
      specificity and active-site base.
    supported_by:
    - reference_id: PMID:8823175
      supporting_text: "The catalytically essential glutamate residue that initiates catalysis by abstracting the substrate alpha-hydrogen as H+ is located at position 376 (mature MCADH numbering) on loop JK in medium chain acyl-CoA dehydrogenase (MCADH)"
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: HTP
  original_reference_id: PMID:34800366
  qualifier: located_in
  review:
    summary: >-
      High-throughput identification of MCAD in the high-confidence human mitochondrial proteome
      (MitoCoP). Confirms mitochondrial localization; less specific than matrix.
    action: KEEP_AS_NON_CORE
    reason: >-
      Mitochondrial localization confirmed by quantitative proteomics; matrix is the precise term.
    supported_by:
    - reference_id: PMID:34800366
      supporting_text: "defined a mitochondrial high-confidence proteome of >1,100 proteins (MitoCoP)"
- term:
    id: GO:0005759
    label: mitochondrial matrix
  evidence_type: IDA
  original_reference_id: PMID:16020546
  qualifier: located_in
  review:
    summary: >-
      Direct localization annotation to the mitochondrial matrix (BHF-UCL). MCAD is a soluble
      matrix flavoenzyme; this is the core, precise location annotation.
    action: ACCEPT
    reason: >-
      Mitochondrial matrix is the experimentally supported, correct subcellular location of MCAD.
- term:
    id: GO:0031966
    label: mitochondrial membrane
  evidence_type: IDA
  original_reference_id: PMID:16020546
  qualifier: located_in
  review:
    summary: >-
      Membrane-association annotation from a submitochondrial fractionation study (whose primary
      subject was the paralog ACAD9). MCAD itself is a soluble matrix enzyme; only weak/transient
      membrane association is expected (e.g. via ETF complex at the inner membrane). The matrix
      annotation is the precise and biologically appropriate location.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      MCAD is a soluble matrix protein, not an integral or stable membrane component; the
      mitochondrial matrix term (GO:0005759) is the accurate location.
- term:
    id: GO:0033539
    label: fatty acid beta-oxidation using acyl-CoA dehydrogenase
  evidence_type: IDA
  original_reference_id: PMID:3597357
  qualifier: involved_in
  review:
    summary: >-
      Direct annotation from purification and characterization of human liver MCAD, which
      identified the octanoyl-CoA dehydrogenation product (2-octenoyl-CoA) and ETF-dependent
      activity. Core process annotation.
    action: ACCEPT
    reason: >-
      Purified human MCAD carries out the ETF-dependent acyl-CoA dehydrogenase step of
      beta-oxidation.
    supported_by:
    - reference_id: PMID:3597357
      supporting_text: "They all utilized electron transfer flavoprotein (ETF) or phenazine methosulfate (PMS) as an electron acceptor"
- term:
    id: GO:0070991
    label: medium-chain fatty acyl-CoA dehydrogenase activity
  evidence_type: IDA
  original_reference_id: PMID:3597357
  qualifier: enables
  review:
    summary: >-
      Direct annotation from purification of human liver MCAD, which converted octanoyl-CoA to
      2-octenoyl-CoA and showed homotetrameric structure with 1 FAD per subunit. Core molecular
      function with classic biochemical support.
    action: ACCEPT
    reason: >-
      Purified human MCAD has medium-chain acyl-CoA dehydrogenase activity; core MF.
    supported_by:
    - reference_id: PMID:3597357
      supporting_text: "The products of SCA dehydrogenase/butyryl-CoA, MCA dehydrogenase/octanoyl-CoA, and IV dehydrogenase/isovaleryl-CoA reactions were identified as crotonyl-CoA, 2-octenoyl-CoA, and 3-methylcrotonyl-CoA"
- term:
    id: GO:0033539
    label: fatty acid beta-oxidation using acyl-CoA dehydrogenase
  evidence_type: IDA
  original_reference_id: PMID:25416781
  qualifier: involved_in
  review:
    summary: >-
      Annotation supported by the METTL20/ETFbeta-KMT study, which assayed MCAD as a model
      ETF-dependent acyl-CoA dehydrogenase and showed ETFbeta methylation reduces electron
      transfer from MCAD. This confirms MCAD operates in the ETF-coupled beta-oxidation step.
    action: ACCEPT
    reason: >-
      MCAD's role in ETF-coupled acyl-CoA dehydrogenase beta-oxidation is directly assayed here.
    supported_by:
    - reference_id: PMID:25416781
      supporting_text: "METTL20-mediated methylation of ETFβ in vitro reduced its ability to receive electrons from the medium chain acyl-CoA dehydrogenase and the glutaryl-CoA dehydrogenase"
- term:
    id: GO:0005634
    label: nucleus
  evidence_type: HDA
  original_reference_id: PMID:21630459
  qualifier: located_in
  review:
    summary: >-
      High-throughput detection of MCAD in a human sperm-nucleus proteome. MCAD is a
      mitochondrial matrix enzyme with a mitochondrial transit peptide; nuclear detection in a
      sperm-nucleus preparation most plausibly reflects residual contamination, despite the
      reported high purity. This is not a credible core localization for an FAO matrix enzyme.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      Nuclear localization is inconsistent with MCAD's mitochondrial targeting and matrix
      function; the single high-throughput sperm-nucleus dataset does not establish a genuine
      nuclear role.
    supported_by:
    - reference_id: PMID:21630459
      supporting_text: "sperm nuclei were obtained through CTAB treatment and isolated to over 99.9% purity without any tail fragments, acrosome or mitochondria"
- term:
    id: GO:0005759
    label: mitochondrial matrix
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-109341
  qualifier: located_in
  review:
    summary: >-
      Reactome traceable-author annotation placing MCAD in the mitochondrial matrix, consistent
      with the experimentally supported location.
    action: ACCEPT
    reason: >-
      Matrix localization is the correct core compartment for MCAD.
- term:
    id: GO:0005759
    label: mitochondrial matrix
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-1989745
  qualifier: located_in
  review:
    summary: >-
      Reactome traceable-author annotation (ACADM expression module) placing MCAD in the
      mitochondrial matrix. Consistent with experimental localization.
    action: ACCEPT
    reason: >-
      Matrix localization is correct.
- term:
    id: GO:0005759
    label: mitochondrial matrix
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-77338
  qualifier: located_in
  review:
    summary: >-
      Reactome traceable-author annotation for the octanoyl-CoA dehydrogenation reaction step,
      placing MCAD in the mitochondrial matrix. Consistent with localization and with MCAD's
      octanoyl-CoA-preferring activity.
    action: ACCEPT
    reason: >-
      Matrix localization is correct; the underlying reaction is MCAD's core activity.
- term:
    id: GO:0005759
    label: mitochondrial matrix
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-77345
  qualifier: located_in
  review:
    summary: >-
      Reactome traceable-author annotation for the decanoyl-CoA dehydrogenation step, placing
      MCAD in the mitochondrial matrix. Consistent with localization and substrate range.
    action: ACCEPT
    reason: >-
      Matrix localization is correct.
- term:
    id: GO:0030424
    label: axon
  evidence_type: IDA
  original_reference_id: PMID:21237683
  qualifier: located_in
  review:
    summary: >-
      Annotation derived from immunohistochemical detection of MCAD in axons of specific
      cerebellar neurons. This reflects cell-type expression of a mitochondrial enzyme within
      neuronal processes (mitochondria are present in axons) rather than a specialized axonal
      localization distinct from the mitochondrion. Retained as a non-core observation.
    action: KEEP_AS_NON_CORE
    reason: >-
      The axonal signal reflects neuronal/mitochondrial expression pattern, not a function-defining
      subcellular compartment for MCAD; the protein remains within mitochondria in those cells.
    supported_by:
    - reference_id: PMID:21237683
      supporting_text: "MCAD in the molecular layer and axons of specific neurons"
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: IDA
  original_reference_id: GO_REF:0000054
  qualifier: located_in
  review:
    summary: >-
      Fusion-protein localization (LIFEdb) to mitochondria, consistent with all other evidence.
      Correct but less specific than matrix.
    action: KEEP_AS_NON_CORE
    reason: >-
      Mitochondrial localization is correct; matrix is the precise core compartment.
    supported_by:
    - reference_id: PMID:1902818
      supporting_text: "Demonstration of intra-mitochondrial mature MCAD indistinguishable in size (42.5-kDa) from control MCAD"
- term:
    id: GO:0051791
    label: medium-chain fatty acid metabolic process
  evidence_type: IDA
  original_reference_id: PMID:1970566
  qualifier: involved_in
  review:
    summary: >-
      Direct annotation from characterization of wild-type and active-site-mutant human MCAD
      expressed in E. coli, which established medium-chain acyl-CoA dehydrogenase function and
      the catalytic base. Core process annotation.
    action: ACCEPT
    reason: >-
      MCAD acts on medium-chain fatty acids; directly supported by enzyme characterization.
    supported_by:
    - reference_id: PMID:1970566
      supporting_text: "Glu376 plays an important role in the initial step of dehydrogenation catalysis"
- term:
    id: GO:0051793
    label: medium-chain fatty acid catabolic process
  evidence_type: IDA
  original_reference_id: PMID:1970566
  qualifier: involved_in
  review:
    summary: >-
      Direct annotation of MCAD's role in medium-chain fatty acid catabolism, from the same
      enzyme-characterization study. Core catabolic process annotation.
    action: ACCEPT
    reason: >-
      MCAD catabolizes medium-chain fatty acids; directly supported.
    supported_by:
    - reference_id: PMID:1970566
      supporting_text: "Glu376 plays an important role in the initial step of dehydrogenation catalysis"
- term:
    id: GO:0070991
    label: medium-chain fatty acyl-CoA dehydrogenase activity
  evidence_type: IDA
  original_reference_id: PMID:19224950
  qualifier: enables
  review:
    summary: >-
      Direct annotation from biochemical characterization of recombinant human MCAD and disease
      variants, including octanoyl-CoA kinetics (WT KM 0.4 uM octanoyl-CoA). Core molecular
      function with strong support.
    action: ACCEPT
    reason: >-
      Purified human MCAD has medium-chain (octanoyl-CoA) dehydrogenase activity; core MF.
    supported_by:
    - reference_id: PMID:19224950
      supporting_text: "Maximum activities (Vmax) and apparent substrate affinities (Km) of octanoyl-CoA oxidation were determined by Michaelis–Menten kinetics"
- term:
    id: GO:0070991
    label: medium-chain fatty acyl-CoA dehydrogenase activity
  evidence_type: IDA
  original_reference_id: PMID:1970566
  qualifier: enables
  review:
    summary: >-
      Direct annotation from the wild-type/active-site-mutant MCAD study; the WT enzyme had
      specific activity 50% of MCAD purified from pig kidney and contained stoichiometric FAD,
      while the catalytic-base mutant was inactive. Core molecular function.
    action: ACCEPT
    reason: >-
      Directly demonstrated medium-chain acyl-CoA dehydrogenase activity dependent on the active-site
      glutamate and FAD.
    supported_by:
    - reference_id: PMID:1970566
      supporting_text: "The wild-type enzyme is a yellow protein due to the content of stoichiometric FAD and had a specific activity which is 50% of MCADH purified from pig kidney"
- term:
    id: GO:0033539
    label: fatty acid beta-oxidation using acyl-CoA dehydrogenase
  evidence_type: IDA
  original_reference_id: PMID:1902818
  qualifier: involved_in
  review:
    summary: >-
      Direct annotation from molecular characterization of MCAD deficiency, which demonstrated
      intra-mitochondrial mature MCAD and showed the K329E (K304E) mutant is inactive due to
      failure to form active tetramers. Supports MCAD's role in the acyl-CoA dehydrogenase step
      of beta-oxidation. Core process.
    action: ACCEPT
    reason: >-
      MCAD function in the ETF-coupled beta-oxidation step is supported; loss abolishes it.
    supported_by:
    - reference_id: PMID:1902818
      supporting_text: "mutant MCAD, which was demonstrated to be inactive, probably because of the inability to form active tetrameric MCAD"
- term:
    id: GO:0070991
    label: medium-chain fatty acyl-CoA dehydrogenase activity
  evidence_type: IDA
  original_reference_id: PMID:1902818
  qualifier: enables
  review:
    summary: >-
      Direct annotation of MCAD medium-chain dehydrogenase activity from the MCAD-deficiency
      characterization, in which expression of the K329E mutant produced inactive enzyme. Core
      molecular function (loss-of-function demonstrates the activity).
    action: ACCEPT
    reason: >-
      The disease mutant abolishes MCAD activity, supporting the medium-chain dehydrogenase MF.
    supported_by:
    - reference_id: PMID:1902818
      supporting_text: "mutant MCAD, which was demonstrated to be inactive, probably because of the inability to form active tetrameric MCAD"
- term:
    id: GO:0019254
    label: carnitine metabolic process, CoA-linked
  evidence_type: IMP
  original_reference_id: PMID:16972171
  qualifier: involved_in
  review:
    summary: >-
      IMP from a clinical exercise study in MCAD-deficient patients. The phenotype observed is
      that patients accumulate octanoylcarnitine and upregulate carnitine biosynthesis to
      compensate for carnitine losses. This is an indirect, downstream metabolic consequence of
      impaired medium-chain FAO (acylcarnitine handling), not a direct enzymatic role of MCAD in
      carnitine metabolism. Per guidelines this experimental annotation is retained but demoted.
    action: KEEP_AS_NON_CORE
    reason: >-
      MCAD's link to carnitine metabolism is secondary, via accumulation/clearance of
      medium-chain acylcarnitines in deficiency, rather than a direct function.
    supported_by:
    - reference_id: PMID:16972171
      supporting_text: "Our results suggest that MCADD patients are able to increase carnitine biosynthesis during exercise to compensate for carnitine losses"
- term:
    id: GO:0033539
    label: fatty acid beta-oxidation using acyl-CoA dehydrogenase
  evidence_type: IMP
  original_reference_id: PMID:16972171
  qualifier: involved_in
  review:
    summary: >-
      IMP from the MCAD-deficiency exercise study: patients showed a substantial rise in plasma
      free fatty acids and octanoylcarnitine during exercise, indicating increased (impaired)
      FAO flux. Supports MCAD's involvement in fatty acid beta-oxidation in vivo. Core process.
    action: ACCEPT
    reason: >-
      Patient phenotype reflects MCAD's in vivo role in medium-chain fatty acid beta-oxidation.
    supported_by:
    - reference_id: PMID:16972171
      supporting_text: "A significant rise in plasma free fatty acids and octanoylcarnitine levels during exercise was seen in all patients, indicating a substantial increase in FAO during exercise"
- term:
    id: GO:0045329
    label: carnitine biosynthetic process
  evidence_type: IMP
  original_reference_id: PMID:16972171
  qualifier: involved_in
  review:
    summary: >-
      IMP linking MCAD deficiency to increased carnitine biosynthesis during exercise. As above,
      this is an indirect compensatory physiological response to acylcarnitine/carnitine
      depletion, not a direct role of MCAD in synthesizing carnitine. Retained but non-core.
    action: KEEP_AS_NON_CORE
    reason: >-
      MCAD does not synthesize carnitine; the association is an indirect compensatory response in
      patients, so it should not be treated as a core MCAD function.
    supported_by:
    - reference_id: PMID:16972171
      supporting_text: "These data suggest an increase in carnitine biosynthesis"
- term:
    id: GO:0003995
    label: acyl-CoA dehydrogenase activity
  evidence_type: IDA
  original_reference_id: PMID:19224950
  qualifier: enables
  review:
    summary: >-
      Direct annotation of the general acyl-CoA dehydrogenase activity from MCAD variant
      characterization. Correct but a broad parent of the specific medium-chain activity.
    action: KEEP_AS_NON_CORE
    reason: >-
      Correct general activity; subsumed by the specific medium-chain dehydrogenase MF.
    supported_by:
    - reference_id: PMID:19224950
      supporting_text: "Maximum activities (Vmax) and apparent substrate affinities (Km) of octanoyl-CoA oxidation were determined by Michaelis–Menten kinetics"
- term:
    id: GO:0033539
    label: fatty acid beta-oxidation using acyl-CoA dehydrogenase
  evidence_type: IDA
  original_reference_id: PMID:19224950
  qualifier: involved_in
  review:
    summary: >-
      Direct annotation from MCAD variant characterization establishing the enzyme's role in the
      acyl-CoA dehydrogenase step of beta-oxidation, with loss-of-function variants causing MCADD.
      Core process.
    action: ACCEPT
    reason: >-
      MCAD carries out the acyl-CoA dehydrogenase step of beta-oxidation; loss causes disease.
    supported_by:
    - reference_id: PMID:19224950
      supporting_text: "MCAD is a member of the acyl-CoA dehydrogenase (ACAD) family of flavoproteins, which catalyzes the first step of the mitochondrial β-oxidation of medium-chain fatty acids"
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IDA
  original_reference_id: PMID:19224950
  qualifier: enables
  review:
    summary: >-
      Annotation reflecting MCAD's homotetrameric assembly (the study analyzed oligomerization and
      showed WT elutes as a tetramer, with disease variants failing to assemble). The
      "identical protein binding" term captures self-association but does not describe MCAD's
      catalytic activity. The homotetramer is the quaternary structure underlying catalysis, and
      its disease relevance is direct: the most common MCAD-deficiency mutation K304E acts by
      misfolding/assembly failure (PMID:1902818, PMID:19224950).
    action: KEEP_AS_NON_CORE
    reason: >-
      Self-association into the homotetramer is real, functionally required, and disease-relevant
      (assembly-defective variants such as K304E cause MCAD deficiency), so it is retained as a
      non-core assembly property rather than marked over-annotated. "identical protein binding" is
      not itself an informative catalytic MF — the core function is the medium-chain acyl-CoA
      dehydrogenase activity that the tetramer enables. Kept consistent with the parallel
      obligate-oligomer annotation on ACADVL GO:0042802, which is likewise KEEP_AS_NON_CORE.
    supported_by:
    - reference_id: PMID:19224950
      supporting_text: "Wild-type MCAD was eluted in the tetrameric form with an almost negligible amount of aggregates"
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: TAS
  original_reference_id: PMID:1731887
  qualifier: located_in
  review:
    summary: >-
      Traceable-author annotation to mitochondrion from the MCAD gene-structure paper. Consistent
      with experimental localization; less specific than matrix.
    action: KEEP_AS_NON_CORE
    reason: >-
      Mitochondrial localization is correct; matrix is the precise core compartment.
    supported_by:
    - reference_id: PMID:1902818
      supporting_text: "Demonstration of intra-mitochondrial mature MCAD indistinguishable in size (42.5-kDa) from control MCAD"
- term:
    id: GO:0003995
    label: acyl-CoA dehydrogenase activity
  evidence_type: IMP
  original_reference_id: PMID:2393404
  qualifier: enables
  review:
    summary: >-
      IMP linking the common K329E (K304E) mutation to loss of MCAD acyl-CoA dehydrogenase
      function. Correct activity (general parent of the medium-chain term). The study established
      the prevalent disease mutation.
    action: KEEP_AS_NON_CORE
    reason: >-
      Correct general activity supported by loss-of-function; the specific medium-chain term is
      the informative core MF.
    supported_by:
    - reference_id: PMID:2393404
      supporting_text: "A single A to G nucleotide replacement which resulted in lysine329-to-glutamic acid329 substitution of the MCAD protein was identified in all cultures"
- term:
    id: GO:0006635
    label: fatty acid beta-oxidation
  evidence_type: IMP
  original_reference_id: PMID:2393404
  qualifier: involved_in
  review:
    summary: >-
      IMP from identification of the common MCAD-deficiency mutation, which impairs medium-chain
      fatty acid beta-oxidation in patients. Core process annotation.
    action: ACCEPT
    reason: >-
      Loss of MCAD (K304E) disrupts fatty acid beta-oxidation, supporting this core process.
    supported_by:
    - reference_id: PMID:2393404
      supporting_text: "Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is one of the most common recessively inherited metabolic diseases in man"
core_functions:
- description: >-
    MCAD catalyzes the FAD-dependent, ETF-coupled alpha,beta-dehydrogenation of medium-chain
    acyl-CoA esters (optimum hexanoyl-/octanoyl-CoA, broadly C4-C12), the first and committed
    step of each cycle of mitochondrial fatty acid beta-oxidation, producing the corresponding
    trans-2-enoyl-CoA. This is the defining molecular function of the enzyme.
  molecular_function:
    id: GO:0070991
    label: medium-chain fatty acyl-CoA dehydrogenase activity
  directly_involved_in:
  - id: GO:0033539
    label: fatty acid beta-oxidation using acyl-CoA dehydrogenase
  - id: GO:0051793
    label: medium-chain fatty acid catabolic process
  locations:
  - id: GO:0005759
    label: mitochondrial matrix
  supported_by:
  - reference_id: PMID:1970566
    supporting_text: "The wild-type enzyme is a yellow protein due to the content of stoichiometric FAD and had a specific activity which is 50% of MCADH purified from pig kidney"
  - reference_id: PMID:8823175
    supporting_text: "The catalytically essential glutamate residue that initiates catalysis by abstracting the substrate alpha-hydrogen as H+ is located at position 376 (mature MCADH numbering) on loop JK in medium chain acyl-CoA dehydrogenase (MCADH)"
  - reference_id: PMID:3597357
    supporting_text: "The products of SCA dehydrogenase/butyryl-CoA, MCA dehydrogenase/octanoyl-CoA, and IV dehydrogenase/isovaleryl-CoA reactions were identified as crotonyl-CoA, 2-octenoyl-CoA, and 3-methylcrotonyl-CoA"
- description: >-
    Cofactor binding required for catalysis. Each MCAD subunit binds one non-covalently
    associated FAD, the redox cofactor that accepts the two electrons removed from the
    acyl-CoA substrate before passing them to ETF; FAD is essential for activity and gives the
    holoenzyme its characteristic yellow color.
  molecular_function:
    id: GO:0050660
    label: flavin adenine dinucleotide binding
  directly_involved_in:
  - id: GO:0006635
    label: fatty acid beta-oxidation
  locations:
  - id: GO:0005759
    label: mitochondrial matrix
  supported_by:
  - reference_id: PMID:1970566
    supporting_text: "The wild-type enzyme is a yellow protein due to the content of stoichiometric FAD"
  - reference_id: PMID:3597357
    supporting_text: "UV/visual spectra, fluorescence spectra, and other evidence indicated that each contains 1 mol of FAD per subunit"
proposed_new_terms: []
suggested_questions:
- question: >-
    What is the in vivo contribution of MCAD to the oxidation of the C12-C14 chain-length range,
    given the overlap with VLCAD/ACAD9, and does this overlap modulate MCAD-deficiency phenotype
    severity across tissues?
- question: >-
    Does reversible lysine acetylation (and SIRT3-mediated deacetylation) of MCAD meaningfully
    regulate medium-chain FAO flux in vivo, or is it a low-stoichiometry modification of limited
    physiological consequence?
suggested_experiments:
- description: >-
    Quantitative substrate-profiling of purified recombinant human MCAD across C4-C16 saturated
    and unsaturated acyl-CoAs using the ETF-coupled assay, to define the precise chain-length
    boundaries and rank-order efficiency that justify the medium-chain vs long-chain MF
    annotations and to test whether the C14/C16 RHEA-derived long-chain annotations are
    physiologically meaningful.
- description: >-
    Tissue-resolved subcellular fractionation plus super-resolution imaging in heart, liver, and
    cerebellar neurons to confirm that MCAD signal in non-canonical compartments (axon, nucleus,
    membrane fractions) is wholly accounted for by mitochondrial matrix localization.
references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO terms
  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:0000052
  title: Gene Ontology annotation based on curation of immunofluorescence data
  findings: []
- id: GO_REF:0000054
  title: Gene Ontology annotation based on curation of intracellular localizations of expressed
    fusion proteins in living cells
  findings: []
- id: GO_REF:0000107
  title: Automatic transfer of experimentally verified manual GO annotation data to orthologs
    using Ensembl Compara
  findings: []
- id: GO_REF:0000116
  title: Automatic Gene Ontology annotation based on Rhea mapping
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:16020546
  title: Human acyl-CoA dehydrogenase-9 plays a novel role in the mitochondrial beta-oxidation
    of unsaturated fatty acids.
  findings:
  - statement: >-
      Used by GOA to support MCAD mitochondrial matrix/membrane localization; the paper's primary
      subject is the paralog ACAD9 and its dimeric, membrane-associated character.
    supporting_text: "Submitochondrial fractionation studies found native ACAD-9 to be associated with the mitochondrial membrane"
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified. This is the ACAD9 characterization paper, not an MCAD study; it is the
      cited support for MCAD's matrix/membrane GO localizations but only informs MCAD indirectly.
      Used here only for localization context.
- id: PMID:16972171
  title: Prolonged moderate-intensity exercise without and with L-carnitine supplementation
    in patients with MCAD deficiency.
  findings:
  - statement: >-
      In MCAD-deficient patients, exercise raised plasma free fatty acids and octanoylcarnitine
      (indicating increased FAO flux) and patients increased carnitine biosynthesis to compensate
      for carnitine losses.
    supporting_text: "A significant rise in plasma free fatty acids and octanoylcarnitine levels during exercise was seen in all patients, indicating a substantial increase in FAO during exercise"
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified clinical study. Supports MCAD's in vivo FAO role; the carnitine-process
      annotations it underpins are indirect compensatory physiology, not direct MCAD functions.
- id: PMID:1731887
  title: Structural organization and regulatory regions of the human medium-chain acyl-CoA
    dehydrogenase gene.
  findings:
  - statement: >-
      Describes the genomic organization and regulatory regions of the human ACADM gene;
      supports mitochondrial localization (TAS).
    supporting_text: "Structural organization and regulatory regions of the human medium-chain acyl-CoA dehydrogenase gene"
- id: PMID:1902818
  title: 'Molecular characterization of medium-chain acyl-CoA dehydrogenase (MCAD) deficiency:
    identification of a lys329 to glu mutation in the MCAD gene, and expression of inactive
    mutant enzyme protein in E. coli.'
  findings:
  - statement: >-
      Established the K329E (K304E) mutation as causative of MCAD deficiency and showed the
      mutant enzyme is inactive due to failure to form active tetramers, while mature MCAD is
      intra-mitochondrial.
    supporting_text: "mutant MCAD, which was demonstrated to be inactive, probably because of the inability to form active tetrameric MCAD"
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified. Direct genetic and biochemical evidence for MCAD function and the
      tetramer-assembly requirement; underpins multiple core annotations.
- id: PMID:19224950
  title: Protein misfolding is the molecular mechanism underlying MCADD identified in newborn
    screening.
  findings:
  - statement: >-
      Recombinant human MCAD is a homotetramer; disease variants (including K304E) cause
      misfolding/aggregation and loss of function. Defines MCAD's domain architecture and
      octanoyl-CoA kinetics.
    supporting_text: "Wild-type MCAD was eluted in the tetrameric form with an almost negligible amount of aggregates"
  - statement: >-
      MCAD is an ACAD-family flavoprotein that catalyzes the first step of mitochondrial
      beta-oxidation of medium-chain fatty acids.
    supporting_text: "MCAD is a member of the acyl-CoA dehydrogenase (ACAD) family of flavoproteins, which catalyzes the first step of the mitochondrial β-oxidation of medium-chain fatty acids"
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified, full text available. Strong support for MCAD molecular function,
      homotetrameric quaternary structure, and the misfolding loss-of-function disease mechanism.
- id: PMID:1970566
  title: Characterization of wild-type and an active site mutant of human medium chain acyl-CoA
    dehydrogenase after expression in Escherichia coli.
  findings:
  - statement: >-
      Recombinant human MCAD is a yellow flavoprotein with stoichiometric FAD; the active-site
      glutamate (Glu376 mature numbering) is the catalytic proton-abstracting base, its mutation
      abolishing activity.
    supporting_text: "The wild-type enzyme is a yellow protein due to the content of stoichiometric FAD and had a specific activity which is 50% of MCADH purified from pig kidney"
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified. Establishes MCAD catalytic activity, FAD content, and the catalytic-base
      mechanism; primary support for the core MF and FAD-binding functions.
- id: PMID:21237683
  title: Identification and characterization of new long chain acyl-CoA dehydrogenases.
  findings:
  - statement: >-
      Characterized the human ACAD family in cerebellum; MCAD was localized to the molecular
      layer and axons of specific neurons, supporting medium-chain dehydrogenase activity and
      neuronal expression.
    supporting_text: "MCAD in the molecular layer and axons of specific neurons"
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified. Primary subject is ACAD10/ACAD11/ACAD9, but MCAD is directly assayed and
      mapped; supports the EXP MF annotation and the (non-core) axon localization.
- id: PMID:21630459
  title: Proteomic characterization of the human sperm nucleus.
  findings:
  - statement: >-
      High-throughput sperm-nucleus proteome in which MCAD was detected; preparation explicitly
      depleted of mitochondria, making the nuclear detection most consistent with residual
      contamination for a matrix enzyme.
    supporting_text: "sperm nuclei were obtained through CTAB treatment and isolated to over 99.9% purity without any tail fragments, acrosome or mitochondria"
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified. Supports the HDA nucleus annotation, which is over-annotated for a
      mitochondrial matrix enzyme; included for completeness.
- id: PMID:2393404
  title: Identification of a common mutation in patients with medium-chain acyl-CoA dehydrogenase
    deficiency.
  findings:
  - statement: >-
      Identified the prevalent K329E (K304E) MCAD mutation present in ~91% of mutant alleles,
      establishing it as the common cause of MCAD deficiency.
    supporting_text: "A single A to G nucleotide replacement which resulted in lysine329-to-glutamic acid329 substitution of the MCAD protein was identified in all cultures"
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified. Foundational genetics of MCAD deficiency; supports the core FAO/activity
      annotations via loss-of-function.
- id: PMID:25416781
  title: Human METTL20 is a mitochondrial lysine methyltransferase that targets the β subunit
    of electron transfer flavoprotein (ETFβ) and modulates its activity.
  findings:
  - statement: >-
      MCAD is one of the ETF-dependent dehydrogenases; methylation of ETFβ by METTL20 reduces
      ETF's ability to receive electrons from MCAD, confirming MCAD operates via ETF in
      beta-oxidation.
    supporting_text: "METTL20-mediated methylation of ETFβ in vitro reduced its ability to receive electrons from the medium chain acyl-CoA dehydrogenase and the glutaryl-CoA dehydrogenase"
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified, full text available. Primary subject is METTL20/ETFβ; MCAD is used as a
      model ETF-coupled dehydrogenase, supporting its ETF-dependent FAO process annotation.
- id: PMID:34800366
  title: Quantitative high-confidence human mitochondrial proteome and its dynamics in cellular
    context.
  findings:
  - statement: >-
      MCAD was identified in the high-confidence human mitochondrial proteome (MitoCoP),
      confirming mitochondrial localization.
    supporting_text: "defined a mitochondrial high-confidence proteome of >1,100 proteins (MitoCoP)"
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified, full text available. High-throughput confirmation of mitochondrial
      localization.
- id: PMID:3597357
  title: Purification and properties of short chain acyl-CoA, medium chain acyl-CoA, and
    isovaleryl-CoA dehydrogenases from human liver.
  findings:
  - statement: >-
      Purified human liver MCAD is a homotetramer with 1 FAD per subunit that converts
      octanoyl-CoA to 2-octenoyl-CoA using ETF as electron acceptor.
    supporting_text: "The products of SCA dehydrogenase/butyryl-CoA, MCA dehydrogenase/octanoyl-CoA, and IV dehydrogenase/isovaleryl-CoA reactions were identified as crotonyl-CoA, 2-octenoyl-CoA, and 3-methylcrotonyl-CoA"
  - statement: >-
      Each of the purified dehydrogenases is a homotetramer (native MW ~178,000 for MCAD) using
      ETF or PMS as electron acceptor.
    supporting_text: "They all utilized electron transfer flavoprotein (ETF) or phenazine methosulfate (PMS) as an electron acceptor"
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified. Classic biochemical characterization of native human liver MCAD;
      establishes homotetramer, FAD content, ETF coupling, and reaction product.
- id: PMID:8823175
  title: 'Medium-long-chain chimeric human Acyl-CoA dehydrogenase: medium-chain enzyme with
    the active center base arrangement of long-chain Acyl-CoA dehydrogenase.'
  findings:
  - statement: >-
      The catalytic base of MCAD is Glu376 (mature numbering) on loop JK; its position
      (versus Glu255 on helix G in LCAD/IVD) is a key determinant of chain-length specificity,
      with native MCAD peaking at hexanoyl/octanoyl-CoA.
    supporting_text: "The catalytically essential glutamate residue that initiates catalysis by abstracting the substrate alpha-hydrogen as H+ is located at position 376 (mature MCADH numbering) on loop JK in medium chain acyl-CoA dehydrogenase (MCADH)"
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified. Defines MCAD active-site base and the structural basis of medium-chain
      specificity; primary support for core MF.
- id: Reactome:R-HSA-109341
  title: dehydrogenation of 4-cis-decenoyl-CoA to form 2-trans-4-cis-decadienoyl-CoA
  findings: []
- id: Reactome:R-HSA-1989745
  title: Expression of ACADM
  findings: []
- id: Reactome:R-HSA-77338
  title: Octanoyl-CoA+FAD => trans-Oct-2-enoyl-CoA+FADH2
  findings: []
- id: Reactome:R-HSA-77345
  title: Decanoyl-CoA+FAD => trans-Dec-2-enoyl-CoA+FADH2
  findings: []