Hydroxylated kininogens and kinins.

Hydroxyprolyl-3-bradykinin was identified in the digest of purified human high molecular weight (H) kininogen with plasma kallikrein. Hydroxyproline was not detected in the heavy and light chains portions of H kininogen, although they include three possible sites for hydroxylation of proline by proline hydroxylase. The content of hydroxyprolyl-3-bradykinin in H kininogen from individual plasmas varied from 14% to 64% of total kinin. The present results and our previous results indicate that only kinin moity in H kininogen from human and monkey plasmas has been partially hydroxylated post-translationally by proline-4-hydroxylase.