SYNTHETIC POLYPEPTIDES AS SUBSTRATES AND INHIBITORS OF COLLAGEN PROLINE HYDROXYLASE

The synthetic polypeptide ([3,4-3H-Pro]-Gly-Pro)n can be hydroxylated by collagen proline hydroxylase. The affinity of the enzyme for the substrate increases with increasing molecular weight of substrate over the range 1300-8000. The data indicate that maximal affinity should be observed with a polypeptide of molecular weight considerably greater than 8000. Poly-L-proline II and (Pro-Gly-Pro)n appear to be com petitive inhibitors of the hydroxylation reaction. The series of oligopeptides, (Glv Pro-Ala)n, (Gly-Pro-MePro)n, (Pro-Gly-Pro)n, and (Pro-Gly-FPro)nPro, were tested for inhibition of hydroxylation over the range n = 1 to n = 4. Inhibition is first observed at n = 2 and for these short oligopeptides is maximal between n = 3 and n = 4. Secondary structure appears to be less important than primary structure in determining whether a peptide will be an inhibitor of the hydroxylase. It is suggested that in a polypeptide chain a specific sequence of 6-9 amino acids is required to identify an appropriate prolyl residue for hydroxylation. Among a series of proline derivatives tested, only 4-fluoro, 3- and 4-methylproline inhibited the hydroxylase. © 1968.