| Feature | Evidence/notes | Key citations (title, year, DOI URL) | PaperQA citation IDs |
|---|---|---|---|
| Verified target identity | Human **P4HA2** corresponds to UniProt **O15460**, encoding the **prolyl 4-hydroxylase subunit alpha-2** alpha isoform of collagen prolyl 4-hydroxylase; belongs to the α-ketoglutarate-dependent dioxygenase family. Family-level reviews explicitly describe P4HA2 as one of the three mammalian catalytic α subunits of C-P4H. | *Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms* (2025), https://doi.org/10.3390/ijms26199371; *Comprehensive analysis revealed P4Hs as new biomarkers for prognosis and immunotherapy in head and neck cancer* (2024), https://doi.org/10.1038/s41598-024-62678-9 | (pqac-00000004, pqac-00000006) |
| Enzyme class | Collagen prolyl 4-hydroxylase (C-P4H) is a **Fe2+/2-oxoglutarate-dependent dioxygenase** that performs prolyl 4-hydroxylation during collagen biosynthesis. | *Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms* (2025), https://doi.org/10.3390/ijms26199371 | (pqac-00000005) |
| Canonical reaction catalyzed | C-P4H hydroxylates proline to **4-hydroxyproline** at the Y position of collagen **-X-Y-Gly-** repeats; this modification is required for collagen triple-helix stability and efficient secretion. | *Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms* (2025), https://doi.org/10.3390/ijms26199371; *Prolyl-4-hydroxylase α subunit 2 promotes breast cancer progression and metastasis by regulating collagen deposition* (2014), https://doi.org/10.1186/1471-2407-14-1 | (pqac-00000004, pqac-00000005) |
| Canonical substrates/motif specificity | Primary substrates are procollagen/collagen sequences containing **-X-Pro-Gly- / -X-Y-Gly-** motifs; high-affinity substrate recognition is linked to **PxGP**-type motifs. Family-level evidence indicates P4HA1 and P4HA2 differ in sequence preference across X-Pro-Gly triplets, supporting isoform-specific substrate bias rather than absolute collagen-type specificity. | *Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms* (2025), https://doi.org/10.3390/ijms26199371; *Comprehensive analysis of the effects of P4ha1 and P4ha2 deletion on post-translational modifications of fibrillar collagens in mouse skin* (2025), https://doi.org/10.3389/fcell.2025.1527839 | (pqac-00000001, pqac-00000002) |
| Required cofactors/cosubstrates | Requires **Fe2+**, **2-oxoglutarate (α-KG)**, and **O2**; **ascorbate** regenerates catalytic Fe2+. | *Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms* (2025), https://doi.org/10.3390/ijms26199371 | (pqac-00000005, pqac-00000012) |
| Reaction products | Hydroxylation of proline is coupled to conversion of α-KG and O2 into **succinate** and **CO2**. | *Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms* (2025), https://doi.org/10.3390/ijms26199371 | (pqac-00000005, pqac-00000012) |
| Key catalytic residues | Family-level structural evidence identifies catalytic metal/cofactor-binding residues corresponding to P4HA2 as **His430, Asp432, His501**. | *Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms* (2025), https://doi.org/10.3390/ijms26199371 | (pqac-00000005) |
| Cellular localization | P4HA2 functions in the **endoplasmic reticulum lumen**; the C-P4H holoenzyme is ER-localized and retained there via the P4HB/PDI **KDEL** sequence. | *Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms* (2025), https://doi.org/10.3390/ijms26199371; *Comprehensive analysis revealed P4Hs as new biomarkers for prognosis and immunotherapy in head and neck cancer* (2024), https://doi.org/10.1038/s41598-024-62678-9 | (pqac-00000004, pqac-00000006, pqac-00000012) |
| Complex composition | Active collagen prolyl 4-hydroxylase is an **α2β2 heterotetramer**; P4HA2 provides the catalytic α subunit and **P4HB/PDI** provides the β subunit. Evidence cited in reviews indicates isoforms assemble as specific α2β2 complexes rather than mixed P4HA1/P4HA2 tetramers. | *Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms* (2025), https://doi.org/10.3390/ijms26199371; *Comprehensive analysis revealed P4Hs as new biomarkers for prognosis and immunotherapy in head and neck cancer* (2024), https://doi.org/10.1038/s41598-024-62678-9 | (pqac-00000001, pqac-00000002, pqac-00000004, pqac-00000006, pqac-00000012) |
| Structural/functional role in collagen biosynthesis | Hydroxylation by P4HA2 stabilizes newly synthesized collagen, enabling proper triple-helix formation, secretion, and extracellular collagen deposition; loss or inhibition reduces collagen deposition in tumor models. | *Prolyl-4-hydroxylase α subunit 2 promotes breast cancer progression and metastasis by regulating collagen deposition* (2014), https://doi.org/10.1186/1471-2407-14-1; *Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms* (2025), https://doi.org/10.3390/ijms26199371 | (pqac-00000004, pqac-00000005) |
| Non-canonical substrate: mTOR | A 2024 mechanistic study showed P4HA2 directly binds **mTOR** and hydroxylates **Pro2341**, increasing mTOR stability, substrate recognition, and downstream signaling (S6K, AKT). This supports a non-collagen signaling role for P4HA2. | *P4HA2 activates mTOR via hydroxylation and targeting P4HA2-mTOR inhibits lung adenocarcinoma cell growth* (2024), https://doi.org/10.1038/s41388-024-03032-1 | (pqac-00000008) |
| Non-canonical substrate: SUFU | A 2024 study in B-cell lymphoma reported that P4HA2 relocates with **KIF7** to the ciliary tip after Hedgehog activation and hydroxylates **SUFU**, inhibiting SUFU and amplifying paracrine Hedgehog signaling. | *P4HA2 hydroxylates SUFU to regulate the paracrine Hedgehog signaling and promote B-cell lymphoma progression* (2024), https://doi.org/10.1038/s41375-024-02313-8 | (pqac-00000009) |
| Regulation by hypoxia/HIF | Reviews and recent analyses place P4HA2 within hypoxia-responsive ECM remodeling programs; hypoxia/HIF signaling upregulates collagen hydroxylation machinery, and P4HA2 is repeatedly linked to hypoxic tumor phenotypes. | *HIFs in hypoxic regulation of the extracellular matrix: focus on little-known player HIF-3* (2024), https://doi.org/10.32604/biocell.2024.048873; *Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms* (2025), https://doi.org/10.3390/ijms26199371 | (pqac-00000002, pqac-00000001) |
| Regulation by SP1 | In colorectal cancer, **SP1** binds the P4HA2 promoter and transcriptionally activates P4HA2, providing direct promoter-level regulatory evidence. | *P4ha2 promotes tumor progression and is transcriptionally regulated by SP1 in colorectal cancer* (2024), https://doi.org/10.1080/15384047.2024.2361594 | (pqac-00000007) |
| Disease/implementation note: biomarker and target | Recent studies consistently report P4HA2 overexpression in multiple cancers and association with worse prognosis, EMT, PI3K/AKT or mTOR pathway activation, and collagen-rich tumor microenvironments; experimental inhibition or knockdown suppresses tumor phenotypes. | *P4ha2 promotes tumor progression and is transcriptionally regulated by SP1 in colorectal cancer* (2024), https://doi.org/10.1080/15384047.2024.2361594; *P4HA2 promotes proliferation, invasion, and metastasis through regulation of the PI3K/AKT signaling pathway in oral squamous cell carcinoma* (2024), https://doi.org/10.1038/s41598-024-64264-5; *P4ha2 contributes to head and neck squamous cell carcinoma progression and EMT through PI3K/AKT signaling pathway* (2024), https://doi.org/10.1007/s12032-024-02358-w; *P4HA2 activates mTOR via hydroxylation and targeting P4HA2-mTOR inhibits lung adenocarcinoma cell growth* (2024), https://doi.org/10.1038/s41388-024-03032-1 | (pqac-00000007, pqac-00000010, pqac-00000011, pqac-00000008) |


*Table: This table summarizes evidence-supported functional annotation for human P4HA2 (UniProt O15460), including its canonical collagen-prolyl hydroxylase role, cofactors, localization, complex assembly, catalytic features, and newer non-canonical substrates. It is useful as a compact reference linking each annotation item to specific literature and PaperQA citation IDs.*