2-氯汞-4-硝基苯酚对人肌肌酸激酶巯基的修饰

本文用含汞试剂MNP修饰人肌肌酸激酶,结果表明,人肌肌酸激酶有6个可反应巯基。MNP首先修饰了一对与活力无关的非必需巯基,增大MNP摩尔比,则进一步修饰另外四个与活性有关的巯基。修饰酶的差吸收光谱、荧光光谱表明这三对巯基的微环境各不相同。其中第二对巯基很可能是位于活性部位的必需巯基,而第三对巯基则是由于第二对巯基,也就是必需巯基,被修饰后,微区构象发生改变而暴露出来的。比较MNP修饰人肌肌酸激酶、鸡胸脯肌肌酸激酶、兔肌肌酸激酶的结果,探讨了MNP对肌酸激酶的修饰以及人肌肌酸激酶可反应巯基的化学微环境。

Thiol Groups of Creatine Kinase From Human Muscle Are Modified by 2-Chloromercuri-4-nitrophenol

When the dimeric enzyme creatine kinase from human muscle was treated with organomercurial, MNP, six SH groups per enzyme molecule able to be modified by MNP were found.Among them,four thiol groups which led to the loss of activity were modified by MNP later than two nonessential ones.Ultraviolet difference spectra and fluoresence spectra of the modified enzymes showed that the microenvironments of three pairs SH groups were different.The second pair of SH groups were probably the essential groups situated in the active sites.After the modification of the Second pair of SH groups, the third pair were exposed as the conformation changes had occurred in the microenvironment.The result showed that with the rapid reaction on the essential SH groups, MNP could inactivate the enzyme completely.It was also worth to notice that a pair of nonessential SH groups situated on the surface were very sensitive to MNP, Compared the results of human creatine kinase,chicken breast creatine kinase and rabbit muscle creatine kinase that were modified by MNP, the modification of creatine kinase by MNP and the microenvironment of the reactive thiol groups were discussed.