Murachi T
Department of Clinical Science and Laboratory Medicine, Kyoto University Faculty of Medicine.
Rinsho Byori. 1990 Apr;38(4):337-46.
Calpain is a Ca2(+)-dependent cysteine endopeptidase and calpastatin is a calpain-specific endogenous inhibitor protein. Both calpain and calpastatin are very widely distributed in various animal tissues and cells. Low (microM) Ca2(+)-requiring calpain I and high (mM) Ca2(+)-requiring calpain II are known to exist. Calpain consists of one heavy (80 kDa) and one light (30 kDa) subunit. The heavy subunits of calpains I and II are different genetic products, whereas the light subunits are the same for both calpains I and II. Molecular cloning as well as protein sequencing revealed that the heavy subunit has four domains, while the light subunit has two domains. The carboxyl terminal domain of each subunit is a calmodulin-like domain, whereas the catalytic site is located in domain 2 of the heavy subunit. Calpastatin has four internally repetitive inhibitory domains. A single domain, or even a truncated 27-mer fragment thereof, possesses inhibitory activity against calpains. Calpain shows a rather broad substrate specificity. It can cleave various enzymes, and cytoskeletal, membrane and receptor proteins. Calpain-catalyzed activation of protein kinase C and transglutaminase may represent a few of the physiological functions of calpain, but a great many other functions can be assigned as well to calpain. Immunohistochemical studies revealed very wide but quite diverse distribution of calpains I and II and calpastatin among various tissues and cells. The expression of the genes for calpain and calpastatin is found to be modulated by retrovirus (HTLV-I) infection to T-lymphocytes. The physiological significance of the calpain and calpastatin system is yet to be elucidated, and accumulating information definitely suggested the role of calpain/calpastatin in health and disease.
钙蛋白酶是一种依赖Ca2(+)的半胱氨酸内肽酶，而钙蛋白酶抑制蛋白是一种钙蛋白酶特异性内源性抑制蛋白。钙蛋白酶和钙蛋白酶抑制蛋白在各种动物组织和细胞中分布非常广泛。已知存在需要低（微摩尔）Ca2(+)的钙蛋白酶I和需要高（毫摩尔）Ca2(+)的钙蛋白酶II。钙蛋白酶由一个重（80 kDa）亚基和一个轻（30 kDa）亚基组成。钙蛋白酶I和II的重亚基是不同的基因产物，而钙蛋白酶I和II的轻亚基是相同的。分子克隆以及蛋白质测序表明，重亚基有四个结构域，而轻亚基有两个结构域。每个亚基的羧基末端结构域是一个钙调蛋白样结构域，而催化位点位于重亚基的结构域2中。钙蛋白酶抑制蛋白有四个内部重复的抑制结构域。单个结构域，甚至其截短的27聚体片段，都具有对钙蛋白酶的抑制活性。钙蛋白酶显示出相当广泛的底物特异性。它可以切割各种酶、细胞骨架、膜和受体蛋白。钙蛋白酶催化的蛋白激酶C和转谷氨酰胺酶的激活可能代表了钙蛋白酶的一些生理功能，但也可以赋予钙蛋白酶许多其他功能。免疫组织化学研究表明，钙蛋白酶I和II以及钙蛋白酶抑制蛋白在各种组织和细胞中的分布非常广泛但相当多样。发现钙蛋白酶和钙蛋白酶抑制蛋白的基因表达受逆转录病毒（HTLV-I）感染T淋巴细胞的调节。钙蛋白酶和钙蛋白酶抑制蛋白系统的生理意义尚待阐明，而不断积累的信息明确提示了钙蛋白酶/钙蛋白酶抑制蛋白在健康和疾病中的作用。
