Sokolov N N, Nikolaev A Ia
Biokhimiia. 1976 Apr;41(4):727-31.
It has been demonstrated that the activity of asparaginase A from Ps. fluorescens AG is completely inhibited by 10(-4) M p-chloromercurybenzoate and by 70-85% by Zn2+, Ca2+ and Cu2+ (2.10(-2) M). Iodoacetate, iodoacetamide, N-ethylimide of maleic acid and 5,5'-dithiobis-(2-nitrobenzoic acid) do not decrease the enzyme activity. Dithiothreitol and beta-mercaptoethanol reactivate the enzyme. L-asparagine, the substrate of asparaginase, protects the enzyme in a large degree against the inhibitory action of p-chloromercurybenzoate. p-chloromercurybenzoate induces a sharp increase in the asparaginase inactivation rate at acidic (6.5--5.5) and alkaline (7.5-8.5) values of pH. The enzyme modification by p-chloromercurybenzoate does not change the Km value for L-asparagine, but decreases Vmax. Thus it may be assumed, that asparaginase from Ps. fluorescens AG contains sulfhydryl groups essential for the enzyme activity.
已证明，荧光假单胞菌AG的天冬酰胺酶A的活性可被10⁻⁴M对氯汞苯甲酸完全抑制，被2.10⁻²M的Zn²⁺、Ca²⁺和Cu²⁺抑制70 - 85%。碘乙酸、碘乙酰胺、马来酸N - 乙基酰亚胺和5,5'-二硫代双（2 - 硝基苯甲酸）不会降低该酶的活性。二硫苏糖醇和β - 巯基乙醇可使该酶重新激活。天冬酰胺酶的底物L - 天冬酰胺在很大程度上保护该酶免受对氯汞苯甲酸的抑制作用。对氯汞苯甲酸在酸性（6.5 - 5.5）和碱性（7.5 - 8.5）pH值下会导致天冬酰胺酶失活速率急剧增加。对氯汞苯甲酸对该酶的修饰不会改变L - 天冬酰胺的Km值，但会降低Vmax。因此可以假定，荧光假单胞菌AG的天冬酰胺酶含有对酶活性至关重要的巯基。
