Anti-prolyl 3-hydroxylase family member 4 (inactive) antibodies are used for the immunodetection of the protein encoded by the P3H4 gene. In humans, the canonical protein has a reported length of 437 amino acid residues and a mass of 50.4 kDa. Its subcellular localization is in the ER. It is notably expressed in fibroblasts. A member of the Leprecan protein family, it is reported to be part of a complex composed of PLOD1, P3H3 and P3H4 that catalyzes hydroxylation of lysine residues in collagen alpha chains and is required for normal assembly and cross-linking of collagen fibrils. Post-translational modifications have been described, including glycosylation. Other names for this target antigen include NO55, NOL55, SC65, endoplasmic reticulum protein SC65, leprecan-like 4, and LEPREL4. Gene orthologs have been identified in the mouse, rat, bovine, frog, chimpanzee and chicken species.