Salamino F, Passalacqua M, Patrone M, Viotti P L, Sparatore B
Institute of Biological Chemistry, University of Genoa, Italy.
Biochem Int. 1990 Aug;21(5):901-8.
Murine erythroleukemia cells contain a single type of calpain classified, on the basis of its calcium requirement, as a type I proteinase. The enzyme is practically inactive at concentrations of calcium below 10 microM and expresses maximal activity in the presence of 0.12-0.15 mM Ca2+. The affinity for Ca2+ cannot be reduced by exposure of the enzyme to conditions known to promote autoproteolysis of calpain. Expression of catalytic activity at lower concentrations of Ca2+, is promoted by the interaction with phospholipid vesicles or plasma membranes. Conditions that promote activation of calpain, induce also the self-inactivation of the enzyme. During terminal differentiation of murine erythroleukemia cells induced by HMBA, the intracellular level of calpain activity undergoes significative reduction. Similar decrease in calpain activity progressively occurs during the loss of sensitivity to HMBA as a result of density growth arrest.
小鼠红白血病细胞含有一种钙蛋白酶，根据其对钙的需求分类，属于I型蛋白酶。该酶在钙浓度低于10微摩尔时几乎无活性，在0.12 - 0.15毫摩尔钙离子存在时表现出最大活性。将该酶暴露于已知能促进钙蛋白酶自蛋白水解的条件下，其对钙离子的亲和力不会降低。与磷脂囊泡或质膜的相互作用可促进在较低钙浓度下催化活性的表达。促进钙蛋白酶激活的条件也会诱导该酶的自我失活。在HMBA诱导的小鼠红白血病细胞终末分化过程中，钙蛋白酶活性的细胞内水平显著降低。由于密度生长停滞导致对HMBA敏感性丧失的过程中，钙蛋白酶活性也会逐渐出现类似的下降。
