Yamauchi T, Sekihara S, Ohsako S
Department of Neurochemistry, Tokyo Metropolitan Institute for Neuroscience, Japan.
Brain Res. 1991 Feb 15;541(2):198-205. doi: 10.1016/0006-8993(91)91019-w.
Calcium/calmodulin-dependent protein kinase II (CaM kinase II) is composed of two distinct but related subunits, alpha and beta, in various ratios. To investigate the physiological significance of this variation, we have studied the effect of autophosphorylation of CaM kinase II isoforms purified from forebrain and cerebellum on the activity, and analyzed their endogenous protein substrates. Autophosphorylation of two kinases resulted in the appearance of Ca2(+)-independent activity and the substrate specificity of the Ca2(+)-independent form differed from that of the Ca2(+)-dependent, non-phosphorylated form of the enzyme. Increased phosphorylation of two kinases resulted in a decrease in the enzyme activity. The decrease in the enzyme activity of forebrain CaM kinase II was larger than that of cerebellar kinase. Phosphorylated forms of two kinases were less stable than the non-phosphorylated forms, and the phosphorylated form of forebrain kinase was less stable than that of cerebellar kinase. Many endogenous protein substrates of respective CaM kinase II were found in both soluble and particulate fractions of forebrain and cerebellum using gel electrophoresis. Although the major protein substrates of CaM kinase II were almost the same in forebrain and cerebellum, some of the endogenous protein substrates of respective CaM kinase II were found to be different in both soluble and particulate fractions of forebrain and cerebellum.
钙/钙调蛋白依赖性蛋白激酶II（CaM激酶II）由两种不同但相关的亚基α和β以不同比例组成。为了研究这种变异的生理意义，我们研究了从前脑和小脑中纯化的CaM激酶II亚型的自身磷酸化对其活性的影响，并分析了它们的内源性蛋白质底物。两种激酶的自身磷酸化导致出现了不依赖Ca2+的活性，且不依赖Ca2+形式的底物特异性不同于依赖Ca2+的、未磷酸化形式的酶。两种激酶磷酸化程度的增加导致酶活性降低。前脑CaM激酶II的酶活性降低幅度大于小脑激酶。两种激酶的磷酸化形式比未磷酸化形式更不稳定，且前脑激酶的磷酸化形式比小脑激酶的更不稳定。使用凝胶电泳在前脑和小脑的可溶性和颗粒部分均发现了各自CaM激酶II的许多内源性蛋白质底物。尽管前脑和小脑中CaM激酶II的主要蛋白质底物几乎相同，但在前脑和小脑的可溶性和颗粒部分均发现各自CaM激酶II的一些内源性蛋白质底物有所不同。
