pInhibition of chicken calpain II by proteins of the cystatin superfamily and alpha 2-macroglobulin was investigated. Human liver cystatins A and B, human cystatin C, chicken cystatin and rat T-kininogen were found not to be inhibitory. Inhibition was, however, observed for bovine and rat kininogens, with Ki (inhibition constant) values of 0.8 nM and 30 nM respectively. alpha 2-Macroglobulin inhibits calpain with an initial rate constant of the order of 3 X 10(4) M-1.S-1. Calpain complexed with alpha 2-macroglobulin showed only limited reactivity towards azocasein, but reacted readily with the peptide substrate Suc-Leu-Tyr-4-methyl-7-coumarylamide and with L-3-carboxy-trans-2,3-epoxypropionyl-leucylamido-(4-guanidin o)butane (E-64). The calpain in the complexes was at least partially protected from loss of activity due to autolysis. The calpain-alpha 2-macroglobulin complexes contained both the calpain subunits./p
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机译：研究了胱抑素超家族和α2-巨球蛋白对鸡钙蛋白酶II的抑制作用。发现人肝胱抑素A和B，人胱抑素C，鸡胱抑素和大鼠T激肽原没有抑制作用。但是，观察到对牛和大鼠激肽原的抑制作用，Ki（抑制常数）值分别为0.8 nM和30 nM。 alpha 2-巨球蛋白抑制钙蛋白酶的初始速率常数约为3 X 10（4）M-1.S-1。钙蛋白酶与α2-巨球蛋白复合仅显示出对偶氮酪蛋白的有限反应性，但容易与肽底物Suc-Leu-Tyr-4-甲基-7-香豆酰胺和与L-3-羧基-反式-2,3-环氧丙酰-基反应。 leucylamido-（4-胍基邻氨基苯甲酸）丁烷（E-64）。由于自溶作用，复合物中的钙蛋白酶至少部分受到保护而免受活性损失。钙蛋白酶-α2-巨球蛋白复合物包含钙蛋白酶的两个亚基。
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