The members of this family are eukaryotic proteins, and include all three isoforms of the prolyl 4-hydroxylase alpha subunit. This enzyme (EC:1.14.11.2) is important in the post-translational modification of collagen, as it catalyses the formation of 4-hydroxyproline. In vertebrates, the complete enzyme is an alpha2-beta2 tetramer; the beta-subunit is identical to protein disulphide isomerase [1-4]. The function of the N-terminal region featured in this family does not seem to be known.

1: Cloning, baculovirus expression, and characterization of a second mouse prolyl 4-hydroxylase alpha-subunit isoform: formation of an alpha 2 beta 2 tetramer with the protein disulfide-isomerase/beta subunit. Helaakoski T, Annunen P, Vuori K, MacNeil IA, Pihlajaniemi T, Kivirikko KI; Proc Natl Acad Sci U S A 1995;92:4427-4431. PMID:7753822

2: Identification and characterization of a third human, rat, and mouse collagen prolyl 4-hydroxylase isoenzyme. Kukkola L, Hieta R, Kivirikko KI, Myllyharju J; J Biol Chem 2003;278:47685-47693. PMID:14500733

3: Prolyl 4-hydroxylase: molecular cloning and the primary structure of the alpha subunit from chicken embryo. Bassuk JA, Kao WW, Herzer P, Kedersha NL, Seyer J, DeMartino JA, Daugherty BL, Mark GE 3rd, Berg RA; Proc Natl Acad Sci U S A 1989;86:7382-7386. PMID:2552442

4: Prolyl 4-hydroxylase alpha-related proteins in Drosophila melanogaster: tissue-specific embryonic expression of the 99F8-9 cluster. Abrams EW, Andrew DJ; Mech Dev 2002;112:165-171. PMID:11850189