Purification and partial characterization of the enzyme for the hydroxylation of proline in protocollagen
Academic Article
Overview
Identity
Additional Document Info
Other
View All
Overview
abstract
A 200-fold purification was obtained for the enzyme which hydroxylates proline residues in protocollagen, the polypeptide precursor of collagen. Essentially all of the enzymic activity was recovered in the soluble protein fraction of chick embryo homogenates. Ferrous iron, ascorbate, and -ketoglutarate were cofactors for the reaction with purified enzyme. The enzyme did not hydroxylate free proline, and it did not hydroxylate either the tripeptide, glycyl-l-prolyl-l-proline, or poly-l-proline II with a molecular weight of about 15,000. The synthetic polytripeptide, (14C-l-prolylglycyl-l-prolyl)n, with a molecular weight of about 4000 was hydroxylated, and the results indicated that the enzyme is specific for proline in the second position after glycine, the position in which the hydroxyproline in collagen is found. A 30-fold purified preparation of the enzyme also hydroxylated lysine residues in protocollagen, and the cofactor requirements were similar to those for the hydroxylation of proline-labeled protocollagen. The question of whether a single enzyme performs both hydroxylations was not resolved, but the general characteristics of the enzyme or enzymes suggest that it might be appropriate to call them protocollagen hydroxylases. 1967.
