Procollagen-Proline Dioxygenase. Procollagen Prolyl 4-Hydroxylase . 4-Hydroxylase, Procollagen Prolyl . Dioxygenase, Procollagen-Proline . Hydroxylase, Protocollagen Prolyl . Procollagen Proline Dioxygenase . Procollagen Prolyl 4 Hydroxylase . Prolyl 4-Hydroxylase, Procollagen . Prolyl Hydroxylase, Protocollagen . Protocollagen Prolyl Hydroxylase . A mixed-function oxygenase that catalyzes the hydroxylation of a prolyl-glycyl containing peptide, usually in PROTOCOLLAGEN, to a hydroxyprolylglycyl-containing-peptide. The enzyme utilizes molecular OXYGEN with a concomitant oxidative decarboxylation of 2-oxoglutarate to SUCCINATE. The enzyme occurs as a tetramer of two alpha and two beta subunits. The beta subunit of procollagen-proline dioxygenase is identical to the enzyme PROTEIN DISULFIDE-ISOMERASES. . 1.00