Prolyl hydroxylase activity in tissue homogenates of annelids from deep sea hydrothermal vents

Tissue homogenates of the deep sea annelids Alvinella caudata and Alvinella pompejana were found to contain enzyme activity resembling vertebrate prolyl 4-hydroxylase. The release of 3H2O from [3,4-(3)H]proline labeled, under-hydroxylated chicken protocollagen type I depended on the presence of the cofactors 2-oxoglutarate, ascorbate, Fe2+ and O2. The release of 3H2O could be inhibited by the prolyl 4-hydroxylase inhibitors zinc, 2,2'-dipyridyl, 3,4-dihydroxybenzoic acid and pyridine-2,4-dicarboxylate, as well as by the synthetic peptide (Pro-Pro-Gly)10. This synthetic peptide could also serve as substrate, because it enhanced the decarboxylation of 2-oxo[5-(14)C]glutarate. Alvinella prolyl hydroxylase appeared to be related to type II vertebrate enzyme because of its lack of affinity for poly (L-proline) and resistance to inactivation by an irreversible peptide inhibitor of chicken prolyl 4-hydroxylase. Maximal enzyme activity was observed in solutions with less than 10% oxygen saturation. By contrast, chicken enzyme was most active at saturating oxygen concentrations. Further data suggest that the Alvinella enzymes are able to accept the 2-oxo acids pyruvate, oxaloacetate and 2-oxoadipinate as substitutes of the cosubstarate 2-oxoglutarate. The data explain the high hydroxylation of Alvinella collagens despite the low oxygen concentrations around hydrothermal vents.