Isolation and identification of hydroxyproline analogues of bradykinin in human urine

Hydroxyproline (Hyp) analogues of bradykinin and lysyl-bradykinin, in which the third residue of bradykinin, proline, is replaced by hydroxyproline, were isolated from human urine. Their amino acid sequences were confirmed by both amino acid and sequence analyses, and also by comparison of their chromatographic behavior with that of synthetic peptides. The possibility that Lys-Ala3-bradykinin, isolated by Mindroiu et al. [(1986) J. Biol. Chem. 261, 7407-7411] from human urine, was actually Lys-Hyp3-bradykinin is discussed.