Prolyl-4-Hydroxylase Alpha Polypeptide III (P4Ha3)

P4HA3 encodes a component of prolyl 4-hydroxylase, a key enzyme in collagen synthesis composed of two identical alpha subunits and two beta subunits. P4HA3 has all residues necessary to bind the peptide substrate, to coordinate Fe(2+) and the 2-oxoglutarate cosubstrate, and for enzymatic activity. Processed P4HA3 contains 525 amino acids and shares 91% and 94% amino acid identity with rat and mouse P4ha3, respectively, and 35% and 37% identity with P4HA1 and P4HA2, respectively. Northern blot analysis detected a 2.7-kb P4HA3 transcript. Highest expression was in placenta, adult liver, and fetal skin, with lower levels in fetal liver, lung, and muscle. RT-PCR detected P4HA3 expression in all tissues examined, with highest expression in placenta and fetal kidney, liver, and lung. Expression of P4HA3 was much lower than that of P4HA1.