Striking susceptibility of a kinin-yielding pentadeca-peptide to tryptic hydrolysis |
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Authors: | Eline S. Prado Misako U. Sampaio F. Galembeck A.C.M. Paiva |
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Affiliation: | Department of Biochemistry and Pharmacology Escola Paulista de Medicina C.P. 20.372, 01000 Sa?o Paulo, S.P., Brazil |
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Abstract: | Hydrolysis of Lys-Arg-Pro-Gly-Phe-Ser-Pro-Phe-Arg-Ser-Val-Gln-Val-Ser by trypsin (EC 3.4.21.4) yields lysyl-bradykinin by rupture of the Arg-Ser bond. The kcat/Km value found for this hydrolysis was 1.4 × 1010 M?1 × sec?1, which is 10?5-fold higher than that obtained for the hydrolysis of bradykinyl-Ser-Val-Gln-Val-Ser. This effect was abolished by acetylation of the lysine amino groups of the pentadecapeptide. Contrarywise, the esterolytic activity of trypsin on bradykinin methyl ester was the same as in lysyl-bradykinin methyl ester. The high susceptibility of Lys-bradykinyl-Ser-Val-Gln-Val-Ser to trypsin catalysis is striking because: a) it constitutes the first example that an amino acid residue distant from the bond split may enhance trypsin catalysis; b) this pentadecapeptide is the best synthetic substrate so far described for trypsin and c) the value of kcat/Km for its hydrolysis is unusually high for proteases. |
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