微量热法研究PCMB对精氨酸酶的抑制作用

Studies on the Inhibiting Action of PCMB to Arginase Using Microcalorimetry

利用微量热法研究了对－氯汞苯甲酸（ＰＣＭＢ）对精氨酸的酶促水解反应的抑制作用，确定它属于竞争性不可逆抑制剂，在２９８．１５Ｋ和ｐＨ为９．４时ＰＣＭＢ与精氨酸酶作用的二级速度常数ｋ＋０＝９２．１７Ｌ／（ｍｏｌ·ｓ）．同时用ＰＣＭＢ作为修饰剂探讨了精氨酸酶的活性中心性质，推测该水解酶至多含有３个与酶活性有关的半胱氨酸残基，但这些残基不属于精氨酸酶的活性中心。

Microcalorimetry was used to study the inhibiting action of p-chloromer curibenzoic acid(PCMB)to L-arginine hydrolysis with arginase, PCMB was determined as a competitive irreversible inhibitor and the second-order rate constant of the reaction between PCMB and arginase was k+0=92. 17 L/(mol· s)at 298.15 K and pH 9.4.The properties of the active site of arginase were investigated by using PCMB as a modifying agent.The results of chemical modification reveal that arginase contains 3 reactive cysteinyl residues at most but these residues do not belong to the active site of arginase. The modification of 3 cysteinyl residues by PCMB led to～50%inhibition of arginase activity.