id: P11511
gene_symbol: CYP19A1
product_type: PROTEIN
status: INITIALIZED
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: >-
  CYP19A1 (aromatase; cytochrome P450 19A1; P-450AROM; estrogen synthase; EC 1.14.14.14) is a
  microsomal, endoplasmic-reticulum-membrane heme-thiolate cytochrome P450 monooxygenase that
  catalyzes the rate-limiting, committed step of estrogen biosynthesis: the aromatization of C19
  androgens to C18 estrogens. In three sequential oxidations, each consuming one molecule of O2 and
  one of NADPH supplied via cytochrome P450 reductase (POR), it removes the C19 angular methyl group
  and aromatizes the steroid A-ring, converting androst-4-ene-3,17-dione (androstenedione) to estrone
  and testosterone to 17beta-estradiol; the first two steps are C19-methyl hydroxylations (19-hydroxy
  then 19-oxo/aldehyde) and the third, unique step is A-ring aromatization with C1-beta hydrogen
  abstraction, C10-C19 bond cleavage, and release of formic acid. The heme iron is axially
  coordinated by a conserved cysteine thiolate, and membrane anchoring via the hydrophobic
  N-terminal segment is required to give lipophilic steroid substrates access to the active site.
  Aromatase is the only vertebrate enzyme that makes estrogens from androgens. It is expressed via
  tissue-specific alternative promoters in the gonads (ovarian granulosa cells, testis), placenta,
  adipose tissue, brain, skin fibroblasts, and bone. Loss of function causes aromatase deficiency
  (virilization, tall stature from unfused epiphyses, and osteoporosis), whereas gain/overexpression
  causes aromatase excess syndrome (gynecomastia and precocity); aromatase is the pharmacological
  target of aromatase-inhibitor therapy (letrozole, anastrozole, exemestane) for estrogen-dependent
  breast cancer. Minor secondary activities include 2-hydroxylation of estrone and oxidation of
  dihydrotestosterone to 19-nor products.
existing_annotations:
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: is_active_in
  review:
    summary: >-
      Aromatase is a microsomal cytochrome P450 that resides in the endoplasmic reticulum, so the
      ER localization is correct. This is a phylogenetic (IBA) annotation consistent with the
      more precise experimental ER-membrane annotations.
    action: ACCEPT
    reason: >-
      Correct compartment; the endoplasmic reticulum membrane (GO:0005789) is the more precise
      location and is the core CC annotation, but the ER parent term is also accurate.
    supported_by:
    - reference_id: PMID:19129847
      supporting_text: >-
        structure of this enzyme of the endoplasmic reticulum membrane
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        Endoplasmic reticulum membrane
- term:
    id: GO:0008585
    label: female gonad development
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: >-
      Estrogen produced by ovarian aromatase is required for normal ovarian follicle development and
      female reproductive function; aromatase deficiency causes multicystic ovaries and delayed
      puberty. This IBA developmental annotation is biologically supported but reflects a downstream
      physiological consequence of estrogen synthesis rather than the enzyme's core molecular role.
    action: KEEP_AS_NON_CORE
    reason: >-
      Accurate but non-core: it captures the developmental/physiological outcome of estrogen
      biosynthesis in the ovary rather than aromatase's catalytic function; retained as non-core.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        aromatase deficiency
- term:
    id: GO:0032355
    label: response to estradiol
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: >-
      Aromatase synthesizes 17beta-estradiol; it is the enzyme that produces estradiol rather than a
      protein whose activity is a cellular response to estradiol. This IBA "response to estradiol"
      term appears to be an over-propagation from the phylogenetic family and does not describe
      aromatase's own function.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      "Response to estradiol" mischaracterizes the direction of the relationship: CYP19A1 is the
      biosynthetic source of estradiol, not a downstream responder. Over-annotated via IBA
      propagation across the aromatase/P450 group.
    propagation_review:
      root_cause: TERM_SCOPING_PROBLEM
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        A cytochrome P450 monooxygenase that catalyzes the conversion
- term:
    id: GO:0070330
    label: aromatase activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: enables
  review:
    summary: >-
      Aromatase activity is the defining, phylogenetically conserved molecular function of CYP19A1
      and is the single most informative core MF term. This IBA is strongly corroborated by multiple
      experimental (EXP/IDA) annotations.
    action: ACCEPT
    reason: >-
      Core molecular function of the gene product, conserved across the aromatase clade and directly
      demonstrated experimentally in human enzyme.
    supported_by:
    - reference_id: PMID:2848247
      supporting_text: >-
        catalyzed the aromatization of androstenedione, testosterone, and 16 alpha-hydroxyandrostenedione
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        A cytochrome P450 monooxygenase that catalyzes the conversion
- term:
    id: GO:0004497
    label: monooxygenase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: >-
      Monooxygenase activity is a correct but very general parent of the specific aromatase activity
      (GO:0070330) that CYP19A1 enables; aromatase is a cytochrome P450 monooxygenase.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      InterPro-derived general term that is an ancestor of the specific, experimentally supported MF
      GO:0070330; over-general for the core function.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        A cytochrome P450 monooxygenase that catalyzes the conversion
- term:
    id: GO:0005506
    label: iron ion binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: >-
      As a heme-thiolate cytochrome P450, aromatase binds a heme prosthetic group whose iron is
      catalytically essential (axially coordinated by Cys437). Iron ion binding is a correct
      cofactor-level MF, supporting but secondary to aromatase activity.
    action: ACCEPT
    reason: >-
      Correct cofactor function (heme iron) demonstrated in the crystal structure; secondary to the
      core catalytic MF.
    supported_by:
    - reference_id: PMID:19129847
      supporting_text: >-
        consists of a haem group and a polypeptide chain of 503 amino-acid residues
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        Name=heme; Xref=ChEBI:CHEBI:30413
- term:
    id: GO:0005789
    label: endoplasmic reticulum membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: >-
      Aromatase is a multi-pass endoplasmic reticulum membrane (microsomal) protein; the UniProt
      SubCell mapping to ER membrane is correct and matches the experimental localization.
    action: ACCEPT
    reason: >-
      Correct core cellular component, consistent with the experimental (EXP/TAS) ER-membrane
      annotations.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        Endoplasmic reticulum membrane
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        Multi-pass membrane protein
- term:
    id: GO:0006703
    label: estrogen biosynthetic process
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  qualifier: involved_in
  review:
    summary: >-
      Estrogen biosynthetic process is the core biological process for aromatase, which performs the
      committed, rate-limiting step converting androgens to estrogens. This ARBA electronic
      annotation is correct and matches the Reactome TAS annotation of the same term.
    action: ACCEPT
    reason: >-
      Core BP: aromatase is the terminal, committed enzyme of estrogen biosynthesis.
    supported_by:
    - reference_id: PMID:19129847
      supporting_text: >-
        the only enzyme in vertebrates known to catalyse the biosynthesis of all oestrogens from androgens
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        A cytochrome P450 monooxygenase that catalyzes the conversion
- term:
    id: GO:0008209
    label: androgen metabolic process
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  qualifier: involved_in
  review:
    summary: >-
      Aromatase consumes C19 androgens (androstenedione, testosterone) as substrates, so it
      participates in androgen metabolism. This is accurate but describes the substrate side of the
      reaction; the productive biological role is estrogen biosynthesis.
    action: KEEP_AS_NON_CORE
    reason: >-
      Substrate-level metabolic term; accurate but secondary to the estrogen biosynthetic process
      that represents the enzyme's core role.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        A cytochrome P450 monooxygenase that catalyzes the conversion
- term:
    id: GO:0016705
    label: oxidoreductase activity, acting on paired donors, with incorporation or
      reduction of molecular oxygen
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: >-
      This is a broad oxidoreductase parent describing the general P450 monooxygenase chemistry
      (incorporation/reduction of O2). It is a correct ancestor of the specific aromatase activity
      but is over-general for the core function.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      General InterPro-derived class; an ancestor of GO:0070330 (aromatase activity) that is already
      annotated experimentally.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        A cytochrome P450 monooxygenase that catalyzes the conversion
- term:
    id: GO:0016712
    label: oxidoreductase activity, acting on paired donors, with incorporation or
      reduction of molecular oxygen, reduced flavin or flavoprotein as one donor,
      and incorporation of one atom of oxygen
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  qualifier: enables
  review:
    summary: >-
      This term describes the EC 1.14.14.- class of monooxygenases using a reduced flavoprotein
      (cytochrome P450 reductase) as the electron donor, which correctly matches the aromatase
      reaction mechanism. However it is a general parent of the specific aromatase activity.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      Correct EC-level parent (P450 monooxygenase using flavoprotein/POR as donor) but over-general;
      the specific MF GO:0070330 is annotated with experimental evidence.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        A cytochrome P450 monooxygenase that catalyzes the conversion
- term:
    id: GO:0020037
    label: heme binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: >-
      Aromatase is a heme-thiolate cytochrome P450; heme binding is a correct, structurally
      confirmed cofactor MF supporting catalysis. Secondary to the core aromatase activity.
    action: ACCEPT
    reason: >-
      Correct cofactor binding demonstrated in the crystal structure (heme with axial Cys437);
      supporting/secondary function.
    supported_by:
    - reference_id: PMID:19129847
      supporting_text: >-
        consists of a haem group and a polypeptide chain of 503 amino-acid residues
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        Name=heme; Xref=ChEBI:CHEBI:30413
- term:
    id: GO:0070330
    label: aromatase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: enables
  review:
    summary: >-
      Automated (UniProt RHEA/EC 1.14.14.14) assignment of the correct core molecular function,
      aromatase activity, consistent with the experimental annotations.
    action: ACCEPT
    reason: >-
      Correct core MF from EC/RHEA mapping; redundant with experimental copies but valid.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        A cytochrome P450 monooxygenase that catalyzes the conversion
- term:
    id: GO:0101021
    label: estrogen 2-hydroxylase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000116
  qualifier: enables
  review:
    summary: >-
      Aromatase displays a minor 2-hydroxylase activity toward estrone (producing 2-hydroxyestrone),
      demonstrated biochemically. This RHEA-mapped MF is a genuine but secondary/minor activity, not
      the core function.
    action: KEEP_AS_NON_CORE
    reason: >-
      Real secondary catalytic activity (estrone 2-hydroxylation) but minor relative to the core
      androgen-aromatization function.
    supported_by:
    - reference_id: PMID:22773874
      supporting_text: >-
        the 2-hydrogen from estrone
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        Also displays 2-hydroxylase activity
- term:
    id: GO:0001541
    label: ovarian follicle development
  evidence_type: IDA
  original_reference_id: PMID:30541132
  qualifier: involved_in
  review:
    summary: >-
      In primary human cumulus granulosa cells, FSH together with oocyte-secreted factors (GDF9/
      BMP15) induces CYP19A1 expression and estradiol production, linking aromatase to follicle
      development and maturation. This is a physiological/developmental role driven by estrogen
      synthesis rather than the core molecular function.
    action: KEEP_AS_NON_CORE
    reason: >-
      Experimentally supported physiological role in the ovarian follicle; retained as non-core
      because it reflects the downstream developmental consequence of aromatase-driven estrogen
      production.
    supported_by:
    - reference_id: PMID:30541132
      supporting_text: >-
        These effects translate into an increase in estradiol production
    - reference_id: PMID:30541132
      supporting_text: >-
        the oocyte have the capacity to regulate the expression of aromatase
- term:
    id: GO:0006703
    label: estrogen biosynthetic process
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-193144
  qualifier: involved_in
  review:
    summary: >-
      Reactome traceable annotation to estrogen biosynthesis, the core biological process of
      aromatase (committed, rate-limiting step converting androgens to estrogens).
    action: ACCEPT
    reason: >-
      Core BP, consistent with the ARBA IEA annotation of the same term and with the enzyme's
      catalytic role.
    supported_by:
    - reference_id: PMID:19129847
      supporting_text: >-
        the only enzyme in vertebrates known to catalyse the biosynthesis of all oestrogens from androgens
- term:
    id: GO:0016125
    label: sterol metabolic process
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-211976
  qualifier: involved_in
  review:
    summary: >-
      Aromatase acts on C19 androgens and produces C18 estrogens, which are steroid hormones, not
      sterols; aromatase does not metabolize sterols (e.g. cholesterol). Sterol metabolic process is
      an over-broad/imprecise grouping for this enzyme.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      Estrogens and their androgen substrates are steroids but not sterols; the reaction belongs to
      steroid/estrogen biosynthesis, so this sterol-metabolism grouping is an over-annotation.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        A cytochrome P450 monooxygenase that catalyzes the conversion
- term:
    id: GO:0005789
    label: endoplasmic reticulum membrane
  evidence_type: EXP
  original_reference_id: PMID:2973313
  qualifier: located_in
  review:
    summary: >-
      The original cloning and immunochemical characterization of human placental aromatase
      established it as a microsomal (ER-membrane) cytochrome P450. Experimental support for the
      core cellular location.
    action: ACCEPT
    reason: >-
      Experimentally supported core cellular component (ER/microsome membrane).
    supported_by:
    - reference_id: PMID:19129847
      supporting_text: >-
        structure of this enzyme of the endoplasmic reticulum membrane
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        Microsome membrane
- term:
    id: GO:0070330
    label: aromatase activity
  evidence_type: EXP
  original_reference_id: PMID:27702664
  qualifier: enables
  review:
    summary: >-
      Recombinant human aromatase and its R264C/R264H variants were characterized by steady-state
      kinetics of androgen-to-estrogen conversion, directly demonstrating aromatase activity.
    action: ACCEPT
    reason: >-
      Direct experimental support for the core molecular function.
    supported_by:
    - reference_id: PMID:27702664
      supporting_text: >-
        The cytochrome P450 aromatase is involved in the last step of sex hormones biosynthesis by converting androgens into estrogens
- term:
    id: GO:0070330
    label: aromatase activity
  evidence_type: EXP
  original_reference_id: PMID:2848247
  qualifier: enables
  review:
    summary: >-
      The full-length human aromatase cDNA expressed in nonsteroidogenic COS-1 cells catalyzed the
      aromatization of androstenedione, testosterone, and 16-alpha-hydroxyandrostenedione, and was
      inhibited by known aromatase inhibitors, directly demonstrating aromatase activity.
    action: ACCEPT
    reason: >-
      Direct experimental support for the core molecular function; establishes that a single
      polypeptide catalyzes the multi-step aromatization.
    supported_by:
    - reference_id: PMID:2848247
      supporting_text: >-
        catalyzed the aromatization of androstenedione, testosterone, and 16 alpha-hydroxyandrostenedione
    - reference_id: PMID:2848247
      supporting_text: >-
        the several steps involved in the aromatization reaction appear to be catalyzed by a single polypeptide chain
- term:
    id: GO:0101021
    label: estrogen 2-hydroxylase activity
  evidence_type: EXP
  original_reference_id: PMID:22773874
  qualifier: enables
  review:
    summary: >-
      Guengerich and colleagues showed experimentally that P450 19A1 removes the 2-hydrogen from
      estrone (2-hydroxylation), a genuine but minor secondary activity distinct from the core
      androgen-aromatization function.
    action: KEEP_AS_NON_CORE
    reason: >-
      Experimentally demonstrated but minor/secondary catalytic activity toward estrone.
    supported_by:
    - reference_id: PMID:22773874
      supporting_text: >-
        the 2-hydrogen from estrone
- term:
    id: GO:0008395
    label: steroid hydroxylase activity
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-193060
  qualifier: enables
  review:
    summary: >-
      Steroid hydroxylase activity is a correct general parent describing the first two (C19
      hydroxylation) steps of the aromatase reaction, but it is over-general relative to the
      specific aromatase activity (GO:0070330).
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      General MF parent of the specific, experimentally supported aromatase activity; over-general
      for the core function.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        Catalyzes three successive
- term:
    id: GO:0008395
    label: steroid hydroxylase activity
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-193143
  qualifier: enables
  review:
    summary: >-
      Duplicate Reactome annotation of the general steroid hydroxylase parent (for the testosterone
      -> estradiol reaction); over-general relative to aromatase activity.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      General MF parent; the specific aromatase activity (GO:0070330) is the informative core term.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        Catalyzes three successive
- term:
    id: GO:0008395
    label: steroid hydroxylase activity
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-5601849
  qualifier: enables
  review:
    summary: >-
      Duplicate Reactome annotation of the general steroid hydroxylase parent (defective-aromatase
      pathway); over-general relative to the specific aromatase activity.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      General MF parent; superseded for the core function by the specific GO:0070330.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        Catalyzes three successive
- term:
    id: GO:0006710
    label: androgen catabolic process
  evidence_type: IDA
  original_reference_id: PMID:26482249
  qualifier: involved_in
  review:
    summary: >-
      In human adipocytes, osteopontin induces aromatase, which consumes testosterone to produce
      estradiol; from the substrate perspective the androgen is catabolized. This is accurate as the
      substrate side of aromatization but is secondary to the productive estrogen-biosynthesis role.
    action: KEEP_AS_NON_CORE
    reason: >-
      Reflects consumption/catabolism of androgen substrate; accurate but non-core relative to
      estrogen biosynthesis.
    supported_by:
    - reference_id: PMID:26482249
      supporting_text: >-
        cOPN more effectively than full-length OPN upregulated aromatase mRNA in adipocytes and significantly increased aromatase protein level and estradiol production
- term:
    id: GO:0070330
    label: aromatase activity
  evidence_type: IDA
  original_reference_id: PMID:26482249
  qualifier: enables
  review:
    summary: >-
      Human adipocytes with induced aromatase converted supplied testosterone to estradiol, directly
      demonstrating aromatase activity in a physiological cell context.
    action: ACCEPT
    reason: >-
      Direct experimental support for the core molecular function in human adipocytes.
    supported_by:
    - reference_id: PMID:26482249
      supporting_text: >-
        the estrogen-synthesizing enzyme aromatase
    - reference_id: PMID:26482249
      supporting_text: >-
        cOPN more effectively than full-length OPN upregulated aromatase mRNA in adipocytes and significantly increased aromatase protein level and estradiol production
- term:
    id: GO:2000866
    label: positive regulation of estradiol secretion
  evidence_type: IDA
  original_reference_id: PMID:26482249
  qualifier: involved_in
  review:
    summary: >-
      Osteopontin-induced aromatase increased estradiol production/secretion by human adipocytes.
      Aromatase enables estradiol output, so its induction positively influences estradiol
      secretion; this is a downstream physiological effect rather than the enzyme's molecular
      function.
    action: KEEP_AS_NON_CORE
    reason: >-
      Physiological/regulatory outcome of aromatase activity; accurate but non-core.
    supported_by:
    - reference_id: PMID:26482249
      supporting_text: >-
        cOPN more effectively than full-length OPN upregulated aromatase mRNA in adipocytes and significantly increased aromatase protein level and estradiol production
- term:
    id: GO:0005789
    label: endoplasmic reticulum membrane
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-5601849
  qualifier: located_in
  review:
    summary: >-
      Reactome traceable annotation to the ER membrane, the core cellular location of the microsomal
      aromatase.
    action: ACCEPT
    reason: >-
      Correct core cellular component; consistent with experimental ER-membrane localization.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        Endoplasmic reticulum membrane
- term:
    id: GO:0005789
    label: endoplasmic reticulum membrane
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-193060
  qualifier: located_in
  review:
    summary: >-
      Duplicate Reactome annotation to the ER membrane (androstenedione -> estrone reaction context);
      correct core location.
    action: ACCEPT
    reason: >-
      Correct core cellular component.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        Endoplasmic reticulum membrane
- term:
    id: GO:0005789
    label: endoplasmic reticulum membrane
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-193143
  qualifier: located_in
  review:
    summary: >-
      Duplicate Reactome annotation to the ER membrane (testosterone -> estradiol reaction context);
      correct core location.
    action: ACCEPT
    reason: >-
      Correct core cellular component.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        Endoplasmic reticulum membrane
- term:
    id: GO:0005789
    label: endoplasmic reticulum membrane
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9707353
  qualifier: located_in
  review:
    summary: >-
      Duplicate Reactome annotation to the ER membrane (aromatase-inhibitor binding context); correct
      core location.
    action: ACCEPT
    reason: >-
      Correct core cellular component.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        Endoplasmic reticulum membrane
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: IDA
  original_reference_id: GO_REF:0000054
  qualifier: located_in
  review:
    summary: >-
      LIFEdb fluorescent-fusion localization to the endoplasmic reticulum, consistent with the
      established microsomal ER-membrane localization of aromatase.
    action: ACCEPT
    reason: >-
      Correct compartment; ER membrane (GO:0005789) is the more precise core location.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        Endoplasmic reticulum membrane
- term:
    id: GO:0020037
    label: heme binding
  evidence_type: IDA
  original_reference_id: PMID:19129847
  qualifier: enables
  review:
    summary: >-
      The crystal structure of human placental aromatase directly demonstrates a bound heme group
      (iron coordinated by Cys437), confirming heme binding as an essential cofactor function.
    action: ACCEPT
    reason: >-
      Direct structural evidence for heme binding; supporting/secondary to the core catalytic MF.
    supported_by:
    - reference_id: PMID:19129847
      supporting_text: >-
        The residues in aromatase involved in haem coordination are Arg 115
    - reference_id: PMID:19129847
      supporting_text: >-
        consists of a haem group and a polypeptide chain of 503 amino-acid residues
- term:
    id: GO:0070330
    label: aromatase activity
  evidence_type: IDA
  original_reference_id: PMID:19129847
  qualifier: enables
  review:
    summary: >-
      Aromatase purified from term human placenta was highly active toward androstenedione and its
      structure captured with the natural substrate, supporting aromatase activity (the enzyme
      catalyzing androgen-to-estrogen conversion).
    action: ACCEPT
    reason: >-
      Experimental/structural support for the core molecular function.
    supported_by:
    - reference_id: PMID:19129847
      supporting_text: >-
        aromatase converts androstenedione, testosterone and 16alpha-hydroxytestosterone to oestrone
- term:
    id: GO:0016712
    label: oxidoreductase activity, acting on paired donors, with incorporation or
      reduction of molecular oxygen, reduced flavin or flavoprotein as one donor,
      and incorporation of one atom of oxygen
  evidence_type: TAS
  original_reference_id: PMID:1371509
  qualifier: enables
  review:
    summary: >-
      General EC 1.14.14.- oxidoreductase parent describing P450-monooxygenase chemistry using a
      flavoprotein electron donor (POR). Correct at the class level but over-general relative to the
      specific aromatase activity.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      Over-general EC-class parent of GO:0070330; the specific MF is the informative core term.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        A cytochrome P450 monooxygenase that catalyzes the conversion
- term:
    id: GO:0009055
    label: electron transfer activity
  evidence_type: TAS
  original_reference_id: PMID:2848247
  qualifier: enables
  review:
    summary: >-
      Electron transfer activity (GO:0009055) is the function of electron-carrier/shuttle proteins.
      Aromatase is the terminal cytochrome P450 oxygenase: it RECEIVES two electrons from NADPH via
      cytochrome P450 reductase (POR) to activate O2, but it is not itself an electron carrier. The
      P450 monooxygenase reaction is captured by aromatase/monooxygenase MF terms, and the cited
      1988 cloning paper does not establish an electron-transfer-carrier function for the enzyme.
    action: REMOVE
    reason: >-
      Mischaracterizes aromatase as an electron carrier; it is a heme-thiolate monooxygenase that
      accepts electrons from POR rather than transferring electrons as a shuttle. Demonstrably wrong
      MF for a terminal P450 oxygenase.
    supported_by:
    - reference_id: PMID:19129847
      supporting_text: >-
        coupling with its redox partner cytochrome P450 reductase
    - reference_id: PMID:1371509
      supporting_text: >-
        Of the enzymes participating in the electron transport system of placental microsomes
- term:
    id: GO:0019825
    label: oxygen binding
  evidence_type: TAS
  original_reference_id: PMID:2848247
  qualifier: enables
  review:
    summary: >-
      Molecular oxygen is a co-substrate activated at the heme iron during each aromatase oxidation
      step. However, oxygen binding (GO:0019825) is typically reserved for O2-carrier/storage
      proteins (e.g. hemoglobin); for a monooxygenase, O2 activation is subsumed by the
      monooxygenase/aromatase MF terms, making this an over-annotation.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      O2 is a reaction co-substrate rather than a carried ligand; the catalytic use of O2 is captured
      by the monooxygenase/aromatase MF terms.
    supported_by:
    - reference_id: PMID:19129847
      supporting_text: >-
        each step requiring 1 mol of O(2), 1 mol of NADPH, and coupling with its redox partner cytochrome P450 reductase
- term:
    id: GO:0006694
    label: steroid biosynthetic process
  evidence_type: TAS
  original_reference_id: PMID:2848247
  qualifier: involved_in
  review:
    summary: >-
      Steroid biosynthetic process is a correct but general parent of the specific estrogen
      biosynthetic process (GO:0006703) that aromatase performs; estrogens are steroid hormones.
    action: KEEP_AS_NON_CORE
    reason: >-
      Accurate general BP; the specific estrogen biosynthetic process is the informative core BP.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        Steroid hormone biosynthesis
- term:
    id: GO:0016020
    label: membrane
  evidence_type: TAS
  original_reference_id: PMID:2848247
  qualifier: located_in
  review:
    summary: >-
      Aromatase is a membrane protein, but "membrane" is an over-general cellular component; the
      specific and correct location is the endoplasmic reticulum (microsome) membrane (GO:0005789).
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      Over-general CC; superseded by the specific ER-membrane annotations.
    supported_by:
    - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
      supporting_text: >-
        Multi-pass membrane protein
core_functions:
- description: >-
    Aromatase activity (EC 1.14.14.14): as a microsomal heme-thiolate cytochrome P450 monooxygenase,
    CYP19A1 catalyzes the committed, rate-limiting step of estrogen biosynthesis, aromatizing C19
    androgens to C18 estrogens (androstenedione -> estrone; testosterone -> 17beta-estradiol) via
    three sequential O2/NADPH-dependent oxidations (two C19-methyl hydroxylations followed by A-ring
    aromatization with C10-C19 cleavage and formate release), receiving electrons from cytochrome
    P450 reductase (POR).
  molecular_function:
    id: GO:0070330
    label: aromatase activity
  directly_involved_in:
  - id: GO:0006703
    label: estrogen biosynthetic process
  locations:
  - id: GO:0005789
    label: endoplasmic reticulum membrane
  supported_by:
  - reference_id: PMID:2848247
    supporting_text: >-
      catalyzed the aromatization of androstenedione, testosterone, and 16 alpha-hydroxyandrostenedione
  - reference_id: PMID:19129847
    supporting_text: >-
      the only enzyme in vertebrates known to catalyse the biosynthesis of all oestrogens from androgens
  - reference_id: file:human/CYP19A1/CYP19A1-uniprot.txt
    supporting_text: >-
      A cytochrome P450 monooxygenase that catalyzes the conversion
- description: >-
    Heme binding: aromatase is a heme-thiolate cytochrome P450 whose heme prosthetic group (iron
    axially coordinated by Cys437) is essential for O2 activation and catalysis; heme/iron binding is
    the supporting cofactor function underpinning the monooxygenase reaction.
  molecular_function:
    id: GO:0020037
    label: heme binding
  locations:
  - id: GO:0005789
    label: endoplasmic reticulum membrane
  supported_by:
  - reference_id: PMID:19129847
    supporting_text: >-
      consists of a haem group and a polypeptide chain of 503 amino-acid residues
  - reference_id: PMID:19129847
    supporting_text: >-
      The residues in aromatase involved in haem coordination are Arg 115
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: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      PAN-GO/GO_Central phylogenetic annotations; the aromatase-activity and ER IBA calls correctly
      capture conserved function, while "response to estradiol" is an over-propagation.
- 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:0000054
  title: Gene Ontology annotation based on curation of intracellular localizations
    of expressed fusion proteins in living cells
  findings: []
- id: GO_REF:0000116
  title: Automatic Gene Ontology annotation based on Rhea mapping
  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:1371509
  title: Biochemical and molecular genetic analyses on placental aromatase (P-450AROM)
    deficiency.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Abstract-only cache; first molecular characterization of an aromatase-deficiency splicing
      mutation, confirming loss of aromatase activity (<0.3% of normal) and microsomal context.
- id: PMID:19129847
  title: Structural basis for androgen specificity and oestrogen synthesis in human
    aromatase.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Full text available; the crystal structure (PDB 3EQM) directly supports heme binding, ER-
      membrane localization, POR electron donation, and the androgen-specific aromatase mechanism.
- id: PMID:22773874
  title: Oxidation of dihydrotestosterone by human cytochromes P450 19A1 and 3A4.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: >-
      Abstract-only cache; supports the minor secondary activities (estrone 2-hydroxylation and DHT
      oxidation to 19-nor products) rather than the core function.
- id: PMID:26482249
  title: Osteopontin promotes aromatase expression and estradiol production in human
    adipocytes.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: >-
      Abstract-only cache; supports aromatase activity in human adipocytes and its induction driving
      estradiol production/secretion (adipose expression, breast-cancer relevance).
- id: PMID:27702664
  title: Impact of R264C and R264H polymorphisms in human aromatase function.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Abstract-only cache; kinetic characterization of recombinant human aromatase and R264 variants
      directly supports aromatase activity (last step of sex-hormone biosynthesis).
- id: PMID:2848247
  title: Isolation of a full-length cDNA insert encoding human aromatase system cytochrome
    P-450 and its expression in nonsteroidogenic cells.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Abstract-only cache; expression in nonsteroidogenic COS-1 cells showed a single polypeptide
      catalyzes aromatization of androstenedione/testosterone (core MF). It does not establish the
      "electron transfer activity" MF that is attributed to it.
- id: PMID:2973313
  title: 'Cloning of a complete cDNA encoding human aromatase: immunochemical identification
    and sequence analysis.'
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Abstract-only cache; original cloning/immunochemical identification of human placental
      aromatase establishing it as a microsomal (ER-membrane) P450.
- id: PMID:30541132
  title: Oocyte-Secreted Factors Synergize With FSH to Promote Aromatase Expression
    in Primary Human Cumulus Cells.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: >-
      Full text available; supports regulation of CYP19A1 expression by FSH + GDF9/BMP15 in human
      cumulus cells and its role in follicular estradiol production.
- id: Reactome:R-HSA-193060
  title: CYP19A1 hydroxylates ANDST to E1
  findings: []
- id: Reactome:R-HSA-193143
  title: CYP19A1 hydroxylates TEST to EST17b
  findings: []
- id: Reactome:R-HSA-193144
  title: Estrogen biosynthesis
  findings: []
- id: Reactome:R-HSA-211976
  title: Endogenous sterols
  findings: []
- id: Reactome:R-HSA-5601849
  title: Defective CYP19A1 does not convert ANDST to E1
  findings: []
- id: Reactome:R-HSA-9707353
  title: CYP19A1 binds Aromatase inhibitors
  findings: []
- id: file:human/CYP19A1/CYP19A1-uniprot.txt
  title: UniProtKB P11511 CYP19A1 (CP19A_HUMAN) record
  findings:
  - statement: >-
      UniProt describes aromatase as a cytochrome P450 monooxygenase that converts C19 androgens
      (androstenedione, testosterone) to C18 estrogens (estrone, 17beta-estradiol) via three
      successive oxidations using O2 and NADPH through cytochrome P450 reductase; it binds heme,
      localizes to the endoplasmic reticulum/microsome membrane as a multi-pass membrane protein, is
      widely expressed (brain, placenta, adipose, gonads), and its loss/gain causes aromatase
      deficiency / aromatase excess syndrome.
    reference_section_type: OTHER
suggested_questions:
- question: >-
    Beyond the well-characterized estrogen-biosynthetic role, do the minor activities (estrone
    2-hydroxylation; dihydrotestosterone oxidation to 19-nor products) have a demonstrable in vivo
    physiological function, e.g. in local androgen homeostasis?
- question: >-
    How does PKA/PKG phosphorylation of aromatase modulate its activity in vivo across the different
    tissue-specific expression contexts (placenta, adipose, brain, gonad)?
suggested_experiments:
- description: >-
    Tissue-specific conditional knockout / promoter-specific expression studies to quantify the
    contribution of each alternative promoter (placental, adipose, brain, gonadal) to circulating
    versus local estrogen pools.
- description: >-
    Reconstituted-membrane kinetic assays with defined POR (and cytochrome b5) stoichiometry to
    dissect how redox-partner availability governs the three sequential oxidation steps and the
    minor 2-hydroxylase activity.