The enzymic hydroxylation of protocollagen models

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Abstract
1. Synthetic polymers of l-prolyl-l-prolylglycine of defined chain length, (Pro-Pro-Gly)n, were found to be substrates for the enzyme protocollagen–proline hydroxylase, with optimum chain length n=5. Boiling the polymer (Pro-Pro-Gly)15 increased its activity as a substrate but had no effect on (Pro-Pro-Gly)5. 2. Protection of both or one of the N- and C-terminal groups made (Pro-Pro-Gly)3 a better substrate, and collagenase digestion of hydroxylated tert.-pentyloxy-carbonyl-(Pro-Pro-Gly)3 benzyl ester indicated that the central prolyl residues were the major points of hydroxylation. 3. The results suggest that the long-chain peptides are optimum substrates but that a triple-stranded structure is inhibitory for hydroxylation.