Abstract
We investigated the ADP-ribosylation of bradykinin by hen liver nuclear ADP-ribosyltransferase. Two Arg residues of the peptide were modified by this enzyme. Arg1 was preferentially modified as compared to Arg9; the Vmax/Km for Arg1 was 3 times higher than that for Arg9. These results were given support by data observed in experiments with des-Arg1 and des-Arg9 bradykinin; the Vmax/Km for des-Arg9 bradykinin was 3 times that for des-Arg1 bradykinin. ADP-ribosylation suppressed the biological activity of bradykinin, as related to both binding and contractile activities. The extent of ADP-ribosylation-induced suppression of both activities was higher in the case of the modification of Arg1 than that of Arg9. In view of the observation of ADP-ribosyltransferase activity in skeletal, cardiac, and smooth muscles (Soman, G. et al. (1984) Biochem. Biophys. Res. Commun. 120, 973-980; Shimoyama, M. et al. (1987) in The 8 th International Symposium on ADP-Ribosylation, Texas, abstract p. 13), bradykinin functioning in the contraction of smooth muscle may be modified in this way in vivo.
