钙调素参与玉米线粒体琥珀酸脱氢酶活性的调节

经DEAE C-32柱纯化的玉米(Zea mays L.)线粒体琥珀酸脱氢酶(SDH),用NAD激酶(NADK)法测定时,无钙调素(CaM)活性,说明不存在游离CaM;而用ELISA法测定总CaM时,却可检测到CaM。纯化的SDH加热处理后,能激活NADK,可能加热释放出游离CaM。纯化SDH的电泳分析表明,天然聚丙烯酰胺凝胶电泳(PAGE)只显示1条主带;而SDS-PAGE则出现67.0kD、30.0kD、16.7kD 3条带,前两条带与SDH的大、小亚基分子量一致,第三条带与CaM电泳迁移率一致。上述结果说明CaM可能与SDH处于结合状态,而且其活性受CaM调节。

CALMODULEV AND THE REGULATION OF SUCCINATE DEHYDROGENASE ACTIVITY IN THE MITOCHONDRIA OF ZEA MAYS

Succinate dehydrogenase (SDH) was purified by DEAE C-32 chromatography from the mitochondrial fraction of com (Zea mays L.) Free calmodulin (CaM) could not be detected in the purified SDH with the method based on the ability of SDH to stimulate NAD kinase, but it still contained some CaM when measured with the ELISA method. Purified SDH could stimulate NAD kinase only after heating to release free CaM. Plain polyacrylamide gel electrophoresis (PAGE) of the purified SDH revealed only one peptide band,but three peptide bands were shown on SDS-PAGE, their molecular weight being 67.0 kD, 30.0 kD, 16.7 kD respectively. The 67.0 kD and 30.0 kD pep-tides corresponded to the large and small molecular subunit of SDH respectively. The Rf value of the 16.7 kD peptide band was identical to the standard CaM in the SDS-PAGE. From all the above evidence , the authors suggested that CaM might exert its function of SDH regulation in a binding state with the SDH molecule.