Identification of [hydroxyproline3]-bradykinin released from human plasma and plasma protein Cohn's fraction IV-4 by trypsin

Aside from bradykinin (BK), a novel kinin, Hydroxyproline3]-bradykinin ( Hyp3]-BK), was isolated from the reaction mixture of human plasma and plasma protein Cohn's fraction IV-4 with trypsin. The liberated kinins were isolated based on procedures which we previously described for the isolation of Hyp3]-lysyl-bradykinin ( Hyp3]-Lys-BK) formed by kallikrein. The ratio of the amounts of two kinins thus formed from human plasma protein Cohn's fraction IV-4 were Hyp3]-BK 25 +/- 4% and BK 75 +/- 4%, similarly to that of Hyp3]-Lys-BK and Lys-BK, formed by kallikrein, but it varied by persons. The isolation of Hyp3]-BK and Hyp3]-Lys-BK suggests that a novel kininogen containing hydroxyproline in the third position of the bradykinin sequence in human plasma protein, possibly undergone post-translational modifications.