id: O15460
gene_symbol: P4HA2
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: >-
  P4HA2 (prolyl 4-hydroxylase subunit alpha-2) is one of three catalytic
  alpha-subunit isoforms of collagen prolyl 4-hydroxylase (C-P4H), an
  endoplasmic reticulum-lumenal enzyme. The active enzyme is an alpha2-beta2
  heterotetramer in which the beta subunit is P4HB (protein disulfide
  isomerase, PDI) acting as a structural and ER-retention subunit; the two
  alpha-2 chains carry the catalytic sites. As a 2-oxoglutarate- and
  Fe(II)-dependent dioxygenase, P4HA2 catalyzes the post-translational
  formation of trans-4-hydroxy-L-proline in -Xaa-Pro-Gly- sequences of
  procollagen (and other proteins), consuming 2-oxoglutarate and O2 and
  producing succinate and CO2. 4-Hydroxyproline is essential for the folding
  and thermal stability of the collagen triple helix. The active-site iron is
  coordinated by a 2-His-1-carboxylate facial triad, and L-ascorbate (vitamin
  C) is required as a cofactor to maintain the iron in the reduced Fe(II)
  state. The type II tetramer contributes a substantial fraction of total
  prolyl 4-hydroxylase activity in human cells, is expressed in heart,
  placenta, lung and pancreas, and does not co-assemble with the type I
  (P4HA1) alpha subunit into mixed tetramers. Variants in P4HA2 cause autosomal
  dominant nonsyndromic high myopia (MYP25), consistent with a role in scleral
  collagen and extracellular matrix.
alternative_products:
- name: IIb
  id: O15460-1
- name: IIa
  id: O15460-2
  sequence_note: VSP_004506
existing_annotations:
- term:
    id: GO:0004656
    label: procollagen-proline 4-dioxygenase activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: enables
  review:
    summary: Phylogenetic inference of the core collagen prolyl 4-hydroxylase activity, conserved across the P4HA family (P4HA1/2/3 and orthologs). This is the defining molecular function of P4HA2.
    action: ACCEPT
    reason: Core molecular function; concordant with direct experimental (IDA, PMID:9211872), TAS and IEA evidence and EC 1.14.11.2.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: Catalyzes the post-translational formation of 4-hydroxyproline in -Xaa-Pro-Gly- sequences in collagens and other proteins.
- term:
    id: GO:0016222
    label: procollagen-proline 4-dioxygenase complex
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: part_of
  review:
    summary: P4HA2 is part of the prolyl 4-hydroxylase complex, the alpha2-beta2 heterotetramer formed with P4HB (PDI). Phylogenetic inference is consistent with the experimentally documented tetramer.
    action: ACCEPT
    reason: Correct complex; P4HA2 assembles with P4HB into the catalytic C-P4H heterotetramer, the cellular form of the enzyme.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: Heterotetramer of two alpha-2 chains and two beta chains (P4HB)
- term:
    id: GO:0004656
    label: procollagen-proline 4-dioxygenase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: enables
  review:
    summary: Electronic assignment of the core dioxygenase activity (RHEA:18945, EC 1.14.11.2), redundant with the experimental IDA annotation.
    action: ACCEPT
    reason: Correct core molecular function; concordant with experimental evidence.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: EC=1.14.11.2
- term:
    id: GO:0005506
    label: iron ion binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: P4HA2 binds one Fe(2+) ion per subunit via a 2-His-1-carboxylate facial triad (His430, Asp432, His501) in the Fe2OG dioxygenase domain; iron binding is essential for the dioxygenase chemistry.
    action: ACCEPT
    reason: Accurate cofactor and active-site chemistry directly supported by the UniProt cofactor line and metal-binding residues; integral to the catalytic mechanism.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: Binds 1 Fe(2+) ion per subunit.
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: located_in
  review:
    summary: Electronic assignment of ER localization, consistent with the documented ER-lumenal residence of the enzyme.
    action: ACCEPT
    reason: Correct compartment; concordant with the UniProt subcellular location and the HPA IDA ER annotation.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.'
- term:
    id: GO:0005788
    label: endoplasmic reticulum lumen
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: Subcellular-location vocabulary mapping to ER lumen, the precise compartment in which the soluble C-P4H tetramer acts on procollagen.
    action: ACCEPT
    reason: Correct and more specific than ER; matches the UniProt subcellular location.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.'
- 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: General dioxygenase parent term capturing the O2-incorporating oxidoreductase chemistry of the 2-oxoglutarate/Fe(II)-dependent reaction.
    action: ACCEPT
    reason: Correct parent of the specific procollagen-proline 4-dioxygenase activity; accurately describes the enzyme oxidoreductase class.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: Reaction=L-prolyl-[collagen] + 2-oxoglutarate + O2 = trans-4-hydroxy-L-prolyl-[collagen] + succinate + CO2
- term:
    id: GO:0031418
    label: L-ascorbic acid binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: L-ascorbate (vitamin C) is a required cofactor that maintains the active-site iron in the reduced Fe(2+) state; ascorbate binding is a documented property of the enzyme.
    action: ACCEPT
    reason: Accurate cofactor binding directly supported by the UniProt cofactor line; mechanistically integral to sustained catalysis.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: Name=L-ascorbate
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:30021884
  qualifier: enables
  review:
    summary: High-throughput crosslinking mass spectrometry (histone interaction landscapes in intact nuclei) capturing P4HA2 interactions with P4HB (the beta subunit of the tetramer) and P4HA1 (the paralogous alpha isoform). The bare protein binding term is uninformative.
    action: KEEP_AS_NON_CORE
    reason: Records real IntAct captures (P4HB, P4HA1) but bare protein binding is uninformative per curation guidelines; the meaningful P4HB interaction is better represented by the complex annotation.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: 'O15460; P07237: P4HB'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:33961781
  qualifier: enables
  review:
    summary: BioPlex/dual proteome-scale interactome screen capturing P4HA2 interactions with P4HB and KIF7. Bare protein binding term is uninformative.
    action: KEEP_AS_NON_CORE
    reason: High-throughput interactome capture; P4HB is the genuine beta subunit but bare protein binding adds no functional specificity, and the KIF7 capture has no established biological meaning for an ER-lumenal enzyme.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: 'O15460; P07237: P4HB'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:35271311
  qualifier: enables
  review:
    summary: OpenCell endogenous-tagging interactome capturing a P4HA2-KIF7 (Q2M1P5) interaction. Bare protein binding term is uninformative.
    action: KEEP_AS_NON_CORE
    reason: High-throughput capture of an interaction without established functional relevance to the collagen-hydroxylation role of P4HA2; bare protein binding is uninformative.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: 'O15460; Q2M1P5: KIF7'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:40205054
  qualifier: enables
  review:
    summary: Multimodal cell-maps interactome capturing P4HA2 interactions with P4HB, P4HA1 and KIF7. Bare protein binding term is uninformative.
    action: KEEP_AS_NON_CORE
    reason: High-throughput interactome capture; the P4HB/P4HA1 captures are consistent with known biology but bare protein binding is uninformative per curation guidelines.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: 'O15460; P13674: P4HA1'
- term:
    id: GO:0016222
    label: procollagen-proline 4-dioxygenase complex
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: part_of
  review:
    summary: Ortholog-based electronic transfer of membership in the prolyl 4-hydroxylase complex, consistent with the experimentally documented alpha2-beta2 tetramer.
    action: ACCEPT
    reason: Correct complex membership; redundant with the IBA complex annotation and the UniProt subunit description.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: Heterotetramer of two alpha-2 chains and two beta chains (P4HB)
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: IDA
  original_reference_id: GO_REF:0000052
  qualifier: located_in
  review:
    summary: Direct immunofluorescence (HPA) evidence for ER localization of P4HA2, consistent with its ER-lumenal site of action.
    action: ACCEPT
    reason: IDA-supported ER localization agrees with the UniProt subcellular location.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.'
- term:
    id: GO:0004656
    label: procollagen-proline 4-dioxygenase activity
  evidence_type: IDA
  original_reference_id: PMID:9211872
  qualifier: enables
  review:
    summary: Direct experimental characterization of the purified human type II (P4HA2) enzyme tetramer demonstrating procollagen-proline 4-dioxygenase activity. This is the core molecular function.
    action: ACCEPT
    reason: Core molecular function with direct experimental (IDA) support; the purified (alpha-II)2-beta2 tetramer hydroxylates collagen prolines.
    supported_by:
    - reference_id: PMID:9211872
      supporting_text: Prolyl 4-hydroxylase (proline hydroxylase, EC 1.14.11.2) catalyzes the formation of 4-hydroxyproline in collagens.
- term:
    id: GO:0005788
    label: endoplasmic reticulum lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-1650808
  qualifier: located_in
  review:
    summary: Reactome curation placing the prolyl 4-hydroxylase reaction in the ER lumen (collagen biosynthesis pathway).
    action: ACCEPT
    reason: Correct compartment; redundant with the UniProt subcellular location and the IEA/IDA ER annotations.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.'
- term:
    id: GO:0005788
    label: endoplasmic reticulum lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9918779
  qualifier: located_in
  review:
    summary: Reactome curation of proline hydroxylase activity in the ER lumen (here in a viral polyprotein-maturation context); the compartment assignment is correct.
    action: ACCEPT
    reason: Correct ER-lumenal compartment; redundant with stronger localization evidence.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.'
- term:
    id: GO:0009055
    label: electron transfer activity
  evidence_type: TAS
  original_reference_id: PMID:9211872
  qualifier: enables
  review:
    summary: P4HA2 is a 2-oxoglutarate/Fe(II)-dependent dioxygenase; although its chemistry is redox-based and ascorbate-dependent, GO:0009055 (electron transfer activity) denotes electron-carrier function in electron transport chains and is a poor fit. The cited paper characterizes the dioxygenase, not an electron-carrier activity.
    action: MARK_AS_OVER_ANNOTATED
    reason: Over-interpretation of the redox/ascorbate chemistry of the enzyme; the informative molecular function is the dioxygenase activity (GO:0004656 / GO:0016705), not electron transfer/carrier activity.
    supported_by:
    - reference_id: PMID:9211872
      supporting_text: Prolyl 4-hydroxylase (proline hydroxylase, EC 1.14.11.2) catalyzes the formation of 4-hydroxyproline in collagens.
- term:
    id: GO:0004656
    label: procollagen-proline 4-dioxygenase activity
  evidence_type: TAS
  original_reference_id: PMID:9211872
  qualifier: enables
  review:
    summary: Author-asserted procollagen-proline 4-dioxygenase activity for the type II enzyme, redundant with the IDA annotation from the same study.
    action: ACCEPT
    reason: Correct core molecular function; concordant with the experimental IDA annotation and EC 1.14.11.2.
    supported_by:
    - reference_id: PMID:9211872
      supporting_text: Prolyl 4-hydroxylase (proline hydroxylase, EC 1.14.11.2) catalyzes the formation of 4-hydroxyproline in collagens.
core_functions:
- description: Catalytic alpha subunit of collagen prolyl 4-hydroxylase that, as part of the alpha2-beta2 heterotetramer with P4HB (PDI), catalyzes 2-oxoglutarate- and Fe(II)-dependent 4-hydroxylation of proline residues in -Xaa-Pro-Gly- sequences of procollagen in the ER lumen, a modification essential for collagen triple-helix stability.
  molecular_function:
    id: GO:0004656
    label: procollagen-proline 4-dioxygenase activity
  locations:
  - id: GO:0005788
    label: endoplasmic reticulum lumen
  in_complex:
    id: GO:0016222
    label: procollagen-proline 4-dioxygenase complex
  supported_by:
  - reference_id: PMID:9211872
    supporting_text: Prolyl 4-hydroxylase (proline hydroxylase, EC 1.14.11.2) catalyzes the formation of 4-hydroxyproline in collagens. The vertebrate enzyme is an alpha2beta2 tetramer, the beta subunit of which is identical to protein disulfide-isomerase (PDI, EC 5.3.4.1).
  - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
    supporting_text: Heterotetramer of two alpha-2 chains and two beta chains (P4HB)
proposed_new_terms:
- proposed_name: peptidyl-proline 4-hydroxylation to 4-hydroxy-L-proline
  proposed_definition: The hydroxylation of peptidyl-proline to peptidyl-4-hydroxy-L-proline catalyzed by P4HA2 as part of collagen biosynthesis (corresponds to the existing term GO:0018401).
  justification: No biological-process annotation is currently present in GOA. The core activity of P4HA2 directly accomplishes peptidyl-proline 4-hydroxylation as part of collagen biosynthesis; existing terms GO:0019471 (peptidyl-proline hydroxylation), GO:0018401 (peptidyl-proline hydroxylation to 4-hydroxy-L-proline) and GO:0032964 (collagen biosynthetic process) would appropriately capture the biological process and should be added rather than newly coined.
  supported_by:
  - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
    supporting_text: Catalyzes the post-translational formation of 4-hydroxyproline in -Xaa-Pro-Gly- sequences in collagens and other proteins.
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:0000107
  title: Automatic transfer of experimentally verified manual GO annotation data to orthologs using Ensembl Compara
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:30021884
  title: Histone Interaction Landscapes Visualized by Crosslinking Mass Spectrometry in Intact Cell Nuclei.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: PubMed-verified crosslinking-MS study; source of IntAct protein binding captures with P4HB and P4HA1. Not focused on P4HA2 function.
- id: PMID:33961781
  title: Dual proteome-scale networks reveal cell-specific remodeling of the human interactome.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: PubMed-verified BioPlex interactome; source of protein binding captures (P4HB, KIF7). High-throughput, not P4HA2-specific.
- id: PMID:35271311
  title: 'OpenCell: Endogenous tagging for the cartography of human cellular organization.'
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: PubMed-verified OpenCell interactome; source of the P4HA2-KIF7 protein binding capture. High-throughput, not P4HA2-specific.
- id: PMID:40205054
  title: Multimodal cell maps as a foundation for structural and functional genomics.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: PubMed-verified multimodal cell-maps interactome; source of protein binding captures (P4HB, P4HA1, KIF7). High-throughput, not P4HA2-specific.
- id: PMID:38654109
  title: P4HA2 activates mTOR via hydroxylation and targeting P4HA2-mTOR inhibits lung adenocarcinoma cell growth.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: 'PubMed-verified (Jin et al., Oncogene 2024). Reports a non-canonical, non-collagen substrate for P4HA2: it binds mTOR directly and hydroxylates the conserved Pro2341 in the mTOR kinase domain, activating mTOR kinase, increasing mTOR stability/substrate recognition and downstream S6K/AKT signaling; a non-hydroxylatable mTOR P2341A mutant reduces lung adenocarcinoma growth. Suggests a cytoplasmic/extra-ER signaling role distinct from the canonical ER-lumenal collagen-hydroxylase function. Notable new mechanism not in the prior review; not elevated to a core annotation here pending independent confirmation.'
- id: PMID:38909089
  title: P4HA2 hydroxylates SUFU to regulate the paracrine Hedgehog signaling and promote B-cell lymphoma progression.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: 'PubMed-verified (Li et al., Leukemia 2024). Reports a second non-canonical P4HA2 substrate: upon Hedgehog activation P4HA2 forms a complex with KIF7, relocalizes to the primary cilium tip, and hydroxylates SUFU, inhibiting SUFU and amplifying Hedgehog signaling; P4HA2 loss impedes B-cell lymphoma progression. Provides a biological rationale for the otherwise-uninformative high-throughput P4HA2-KIF7 interactome captures (PMID:33961781, PMID:35271311, PMID:40205054). New mechanism not in the prior review; non-core pending independent confirmation.'
- id: PMID:38857058
  title: P4HA2 promotes tumor progression and is transcriptionally regulated by SP1
    in colorectal cancer.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: 'PubMed-verified (Dang et al., Cancer Biol Ther 2024; DOI 10.1080/15384047.2024.2361594).
      Provides promoter-level mechanistic evidence that the transcription factor SP1
      binds the P4HA2 promoter (ChIP) and activates its transcription in colorectal
      cancer; P4HA2 overexpression promotes proliferation and EMT, with AGO1 implicated
      as a downstream effector. Upstream transcriptional-regulation context (non-core
      for the catalytic annotation) that complements the hypoxia/HIF induction axis.'
- id: PMID:41096640
  title: Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer
    Progression via Both Canonical and Non-Canonical Mechanisms.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: 'PubMed-verified review (Hironaka & Xiong, Int J Mol Sci 2025; DOI
      10.3390/ijms26199371). Reviews C-P4H structure/function, the alpha2-beta2/PDI
      tetramer, ER localization, Fe(II)/2-oxoglutarate/O2/ascorbate chemistry, and
      both canonical (collagen deposition) and non-canonical (signaling-protein hydroxylation,
      stemness, hypoxia, metabolism) cancer mechanisms of the C-P4HA alpha subunits.
      Family-level/secondary review context corroborating the core enzymology and
      the emerging non-canonical-substrate findings (mTOR/SUFU); not primary evidence.'
- id: PMID:32969070
  title: Prolyl and lysyl hydroxylases in collagen synthesis.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: 'PubMed-verified authoritative review (Salo & Myllyharju, Exp Dermatol 2021). Comprehensive review of collagen prolyl 4-hydroxylases (including P4HA1/2/3), 3-hydroxylases and lysyl hydroxylases, covering enzymology, the alpha2-beta2/PDI tetramer, ER localization, biological function and disease. Supports the core enzymatic/complex/localization framing of P4HA2; also notes no collagen-hydroxylase inhibitor is yet in clinical use (in contrast to HIF-PHD inhibitors).'
- id: PMID:9211872
  title: Cloning of the human prolyl 4-hydroxylase alpha subunit isoform alpha(II) and characterization of the type II enzyme tetramer. The alpha(I) and alpha(II) subunits do not form a mixed alpha(I)alpha(II)beta2 tetramer.
  findings:
  - statement: The human type II prolyl 4-hydroxylase is an (alpha-II)2-beta2 tetramer with P4HB/PDI as the beta subunit and catalyzes formation of 4-hydroxyproline in collagens (EC 1.14.11.2).
    reference_section_type: ABSTRACT
  - statement: The alpha(I) and alpha(II) subunits do not co-assemble into a mixed alpha(I)alpha(II)beta2 tetramer; the type II enzyme is kinetically similar to type I except for a much higher Ki for poly(L-proline).
    reference_section_type: ABSTRACT
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Definitive characterization of human P4HA2; establishes the catalytic activity, cofactors and the alpha2-beta2 tetramer with P4HB. Anchors the IDA/TAS activity annotations.
- id: Reactome:R-HSA-1650808
  title: Prolyl 4-hydroxylase converts collagen prolines to 4-hydroxyprolines
  findings: []
- id: Reactome:R-HSA-9918779
  title: Proline hydroxylases hydroxylate Polyprotein
  findings: []
- id: file:human/P4HA2/P4HA2-uniprot.txt
  title: UniProt entry O15460 (P4HA2_HUMAN), Prolyl 4-hydroxylase subunit alpha-2
  findings:
  - statement: ER-lumenal 2-oxoglutarate/Fe(II)-dependent dioxygenase (EC 1.14.11.2) that 4-hydroxylates collagen prolines; alpha2-beta2 heterotetramer with P4HB; binds Fe(2+) and L-ascorbate; variants cause high myopia (MYP25).
    reference_section_type: OTHER
suggested_questions:
- question: Do the type I (P4HA1) and type II (P4HA2) collagen prolyl 4-hydroxylases have distinct procollagen substrate or tissue preferences that explain why P4HA2 deficiency manifests primarily as scleral/ocular (high myopia) rather than systemic connective-tissue disease?
- question: Does the high-throughput KIF7 interaction reflect a genuine extra-catalytic role for P4HA2, or is it an incidental interactome capture?
suggested_experiments:
- description: Reconstitute the recombinant (alpha-II)2-beta2 tetramer and measure steady-state kinetics on defined procollagen peptide substrates, comparing P4HA2 with P4HA1 to define isoenzyme-specific substrate preferences.
- description: Knock out or knock down P4HA2 in scleral fibroblasts and quantify collagen 4-hydroxyproline content, triple-helix thermal stability and ECM deposition to test the mechanistic link to high myopia.
- description: Express the MYP25 variants (e.g. E291K) and assay protein abundance, tetramer assembly with P4HB, and residual dioxygenase activity to clarify the loss-of-function mechanism.