败血症大鼠心肌肌浆网phospholamban蛋白磷酸酶活性的变化

ALTERATION OF PHOSPHOLAMBAN PHOSPHATASE ACTIVITY ASSOCIATED WITH CARDIAC SARCOPLASMIC RETICULUM DURING SEPSIS IN RATS

用ＤＥＡＥ－Ｓｅｐｈａｃｅｌ层析法部分纯化了大鼠心肌肌浆网ｐｈｏｓｐｈｏｌａｍｈａｎ（ＰＬＢ）蛋白磷酸酶（ＰＰａｓｅ），并证明其是ＰＰａｓｅ－１。在ＳＤＳ－ＰＡＧＥ电泳放射自显影上证明，ＥＳ大鼠心肌ＳＲ部分纯化的ＰＬＢＰＰａｓｅ对底物（３２Ｐ－磷酸化酶ａ和３２Ｐ－ＳＲ）的去磷酸化作用明显减弱；ＬＳ大鼠该部分纯化的ＰＰａｓｅ对底物的去磷酸化作用和健康大鼠相比未见明显变化。测定败血症大鼠心肌ＳＲ及其部分纯化的ＰＬＢＰＰａｓｅ活性的结果表明，ＥＳ大鼠该酶活性明显降低；但ＬＳ大鼠该酶活性无显著变化。上述结果在该部分纯化ＰＰａｓｅ的底物浓度（酶浓度、时间）－酶反应速度曲线及酶抑制曲线和激活曲线上也同时被充分证明。进一步研究证实，ＥＳ大鼠该部分纯化的ＰＬＢＰＰａｓｅ对底物的亲合力降低（Ｋｍ升高），酶最大反应速度（Ｖｍａｘ）下降；ＬＳ大鼠该部分纯化的ＰＰａｓｅ对底物的亲合力和Ｖｍａｘ与健康对照组大鼠相似未见明显变化。上述结果表明，ＥＳ大鼠心肌ＳＲ部分纯化的ＰＬＢＰＰａｓｅ活性明显降低；ＬＳ大鼠该酶活性无显著变化。

In the present study, rat cardiac sarcoplasmic reticulum(SR) phospholamban (PLB) phosphatase was partially purified by chromatography on DEAE-Sephacel.This PLB phosphatase was indentical to phosphatase-1.It was shown on electrophoresis of SDS-PAGE autoradiography that the PLB phosphatase in rats during early sepsis(ES)depressed dephosphorylation of substrates (32P-phosphorylase a and 32P-SR). However,dephosphorylation of the substrates by the partially purified phosphatase during late sepsis (LS) was same as that in control rats. The partially purified PLB phosphatase activity in ES rats was significantly decreased, but showed no change in LS rats. The results above were confirmed by a studing of the substrate concentration (enzyme concentration,time) -enzyme reaction velocity curve in showing that both affinity and maximum initial velocity (Vmax) of the phosphatase in the ES rats were decreased, but had no change in those in the LS rats.