Multiple determinants for the high substrate specificity of an angiotensin II-forming chymase from the human heart.

摘要: Human heart chymase, a chymotrypsin-like serine proteinase that hydrolyzes the Phe8-His9 bond in angiotensin I (Ang I) to yield octapeptide hormone II II) and His-Leu, is most specific, efficient Ang II-forming enzyme described. Other mammalian chymases display much broader substrate specificity. To better define its specificity, we have mapped extended substrate-binding site of human chymase using analogs. The has preference for aromatic amino acids phenylalanine, tyrosine, tryptophan at P1 site. At S2 subsite there significant proline over hydrophobic or hydrophilic acids. There no clear S'1 S'2 subsites, but an analog containing P'1 not hydrolyzed one with P'2 poorly. An increasing reduction reactivity occurs when P position are deleted sequentially from N terminus. increase decrease length His-Leu leaving group also produces marked reactivity. No single determinant preeminently required catalysis, several factors acting synergistically appear be important. Thus, propose ideal substrates should contain structure nXaa-Pro-[Phe, Tyr, Trp]-Yaa-Yaa, where n greater than equal 6; Xaa = any acid; Yaa acid except proline. This exists neurotensin, both which good chymase. These findings indicate selection scissile by more restricted other chymases.