| Category | Summary | Key evidence (cite first-author year) | URL | Publication date |
|---|---|---|---|---|
| Identity/Names | Human **P3H2** corresponds to **LEPREL1** (also called Leprecan-like protein 1), one of three vertebrate prolyl 3-hydroxylase isoenzymes; it belongs to the leprecan family and contains a C-terminal 2-oxoglutarate-dependent dioxygenase catalytic domain. Literature distinguishes it from paralogs **P3H1/LEPRE1** and **P3H3/LEPREL2**, which is important because substrate specificities differ. (pqac-00000001, pqac-00000009, pqac-00000011) | Marini 2007; Gjaltema 2017 | https://doi.org/10.4161/cc.6.14.4474 ; https://doi.org/10.1080/10409238.2016.1269716 | 2007-07 ; 2017-01 |
| Enzymatic reaction | P3H2 is a **prolyl 3-hydroxylase** that catalyzes formation of **3-hydroxyproline (3Hyp)** on collagen chains, hydroxylating proline residues in collagenous Gly-X-Y motifs; reviews and primary studies identify collagen IV as its main physiological substrate. (pqac-00000000, pqac-00000002, pqac-00000004, pqac-00000020, pqac-00000021) | Pasanen 2011; Aypek 2022; Salo & Myllyharju 2021; Montgomery 2018 | https://doi.org/10.1172/jci147253 ; https://doi.org/10.1111/exd.14197 ; https://doi.org/10.1074/jbc.ra117.000406 | 2011 ; 2022-05 ; 2021-10 ; 2018-04 |
| Cofactors | As a member of the **2-oxoglutarate/Fe(II)-dependent dioxygenase** family, P3H2 requires **Fe2+**, **2-oxoglutarate**, **O2**, and **ascorbate** for catalysis, consistent with the catalytic chemistry of collagen hydroxylases. (pqac-00000004, pqac-00000005, pqac-00000010, pqac-00000018) | Pasanen 2011; Onursal 2023; Fonsén 2007 | https://doi.org/10.1101/2023.06.28.546985 | 2011 ; 2023-06 ; 2007 |
| Substrate specificity | Evidence supports **collagen IV** as the principal substrate of P3H2. Recombinant/enrichment studies place P3H2 in basement-membrane-rich tissues and show greater activity on peptide substrates representing **type IV collagen** hydroxylation sites than on type I collagen sites; type IV collagen is likely the major substrate, though P3H2 may also modify other collagens to a lesser extent. (pqac-00000000, pqac-00000003, pqac-00000004, pqac-00000021, pqac-00000023) | Pasanen 2011; Montgomery 2018; Salo & Myllyharju 2021; Pignata 2021 | https://doi.org/10.1074/jbc.ra117.000406 ; https://doi.org/10.1111/exd.14197 ; https://doi.org/10.3390/ijms22083896 | 2011 ; 2018-04 ; 2021-10 ; 2021-04 |
| Subcellular localization | P3H2 is reported as **endoplasmic reticulum (ER)-localized**, with some evidence also noting ER/Golgi network localization; family-level evidence indicates ER-association/ER-retention features for prolyl 3-hydroxylases. In podocytes and endothelial cells, localization is consistent with a secretory-pathway collagen-modifying enzyme. (pqac-00000000, pqac-00000002, pqac-00000011, pqac-00000013) | Marini 2007; Pignata 2021; Aypek 2022 | https://doi.org/10.4161/cc.6.14.4474 ; https://doi.org/10.3390/ijms22083896 ; https://doi.org/10.1172/jci147253 | 2007-07 ; 2021-04 ; 2022-05 |
| Biological role/pathways | P3H2 functions in the **collagen biosynthesis/post-translational modification pathway** for basement membranes, especially the **glomerular basement membrane (GBM)** and vascular basement membrane. By generating 3Hyp on collagen IV, it influences collagen IV organization and interactions with binding partners such as **nidogens 1/2** and **glycoprotein VI**; it is also induced by **VEGF-A/VEGFR2/p38 MAPK** signaling in endothelial cells, linking collagen IV modification to angiogenesis. (pqac-00000003, pqac-00000007, pqac-00000012, pqac-00000022) | Montgomery 2018; Pignata 2021; Aypek 2022 | https://doi.org/10.1074/jbc.ra117.000406 ; https://doi.org/10.3390/ijms22083896 ; https://doi.org/10.1172/jci147253 | 2018-04 ; 2021-04 ; 2022-05 |
| Key phenotypes/disease links | Loss or mutation of P3H2/LEPREL1 is linked to **ocular disease** (autosomal-recessive high myopia with early cataract/vitreoretinal degeneration) and to **renal disease** including **thin basement membrane nephropathy (TBMN)** and **focal segmental glomerulosclerosis (FSGS)**. In the kidney, podocyte-specific loss causes thinner GBM with progressive **microhematuria** and **microalbuminuria**; in human pedigrees, truncating variants have been reported. (pqac-00000007, pqac-00000017, pqac-00000021, pqac-00000022, pqac-00000023) | Tekin 2013; Aypek 2022; Montgomery 2018; Pignata 2021; Salo & Myllyharju 2021 | https://doi.org/10.1172/JCI65853 ; https://doi.org/10.1172/jci147253 ; https://doi.org/10.1074/jbc.ra117.000406 ; https://doi.org/10.3390/ijms22083896 ; https://doi.org/10.1111/exd.14197 | 2013-05 ; 2022-05 ; 2018-04 ; 2021-04 ; 2021-10 |
| Therapeutic/real-world applications | P3H2 currently has **no established approved therapy** directly targeting it, but experimental work suggests translational potential in **anti-angiogenic therapy**: P3H2 knockdown reduced pathological angiogenesis in a laser-induced choroidal neovascularization model. In nephrology, P3H2 is emerging as a **disease gene and GBM modifier** relevant to diagnosis/mechanistic interpretation of TBMN/FSGS. (pqac-00000007, pqac-00000022) | Pignata 2021; Aypek 2022 | https://doi.org/10.3390/ijms22083896 ; https://doi.org/10.1172/jci147253 | 2021-04 ; 2022-05 |
| Key quantitative data | Reported quantitative details include: **P3H2 modifies ~10–15 proline residues per 1000 amino acids in collagen IV**, whereas **P3H1 modifies ~1 per 1000 aa in collagen I**; type IV collagen α1 chain contains about **15 3Hyp residues**; VEGF-A-stimulated HUVEC RNA-seq identified **459 differentially expressed genes** including P3H2; myopia affects **>25%** of adults in Western Europe/America and **>70%** in some urban East Asian populations, while **high myopia** affects about **1–3%** of the population. A human renal pedigree described a **c.1213C>T** nonsense variant causing premature truncation. (pqac-00000012, pqac-00000023, pqac-00000017, pqac-00000007) | Pignata 2021; Salo & Myllyharju 2021; Tekin 2013; Aypek 2022 | https://doi.org/10.3390/ijms22083896 ; https://doi.org/10.1111/exd.14197 ; https://doi.org/10.1172/JCI65853 ; https://doi.org/10.1172/jci147253 | 2021-04 ; 2021-10 ; 2013-05 ; 2022-05 |


*Table: This table summarizes the core functional annotation of human P3H2/LEPREL1 (UniProt Q8IVL5), including enzymatic activity, localization, substrates, disease links, and quantitative findings. It condenses the most relevant supported evidence for rapid reference in the final report.*