SUBSTRATE SPECIFICITY OF COLLAGEN PROLINE HYDROXYLASE - HYDROXYLATION OF A SPECIFIC PROLINE RESIDUE IN BRADYKININ

In animal tissues hydroxyproline is synthesized by the enzymic hydroxylation of selected proline residues in peptide linkage by collagen proline hydroxylase. Although proline residues susceptible to hydroxylation are apparently recognized on the basis of their position in specific amino acid sequences, the requirements for recognition of such sequences by the enzyme appear to be relatively simple. Polytripeptides of the form H(Gly-Pro-Pro)nOH can serve as substrates for the hydroxylase when they attain a molecular weight of about 1000 (1, 2). Hutton et al. (3) found that 37% of the hydroxyproline synthesized in vitro is located in Gly-Pro-Hyp sequences. Bornstein (4) determined the sequence of a fragment of one of the collagen chains and showed that every hydroxyproline-containing sequence is of the form Gly-X-Hyp-Gly, where X may be Leu, Pro, Ala, or Glu. We have recently found that the peptide hormone bradykinin, H-Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg-OH, can serve as a substrate of collagen proline hydroxylase. The availability of suitably labeled forms of bradykinin has made it possible to further characterize the recognition site for collagen proline hydroxylase. © 1969.