Malliopoulou T B, Rakitzis E T, Malliopoulou V A
Department of Biological Chemistry, University of Athens Medical School, Greece.
J Enzyme Inhib. 1990;4(1):27-34. doi: 10.3109/14756369009030385.
The rate of rhodanese inactivation by 2,4,6-trinitrobenzenesulphonate is increased in the presence of diethylbarbiturate in the reaction medium. A "rate saturation effect" indicates the formation of a rhodanese-diethylbarbiturate complex, prior to modification-induced enzyme inactivation. The dissociation constant of this complex is 19.0 mM. Diethylbarbiturate has no effect on the trinitrophenylation rate of the free amino groups of rhodanese. When rhodanese modification, in the presence of diethylbarbiturate in the reaction medium, is carried out by the use of a 2,4,6-trinitrobenzenesulphonate concentration much lower than the concentration of rhodanese modifiable amino groups, reaction stoichiometry indicates that 3 to 5 moles of rhodanese are rendered inactive for each mole of 2,4,6-trinitrobenzenesulphonate utilized. This finding indicates the existence of a chain-reaction type mechanism of rhodanese inactivation.
在反应介质中存在二乙巴比妥酸盐的情况下，2,4,6-三硝基苯磺酸盐使硫氰酸酶失活的速率会增加。“速率饱和效应”表明在修饰诱导的酶失活之前，形成了硫氰酸酶-二乙巴比妥酸盐复合物。该复合物的解离常数为19.0 mM。二乙巴比妥酸盐对硫氰酸酶游离氨基的三硝基苯化速率没有影响。当在反应介质中存在二乙巴比妥酸盐的情况下，使用比硫氰酸酶可修饰氨基浓度低得多的2,4,6-三硝基苯磺酸盐浓度对硫氰酸酶进行修饰时，反应化学计量表明，每利用1摩尔2,4,6-三硝基苯磺酸盐，有3至5摩尔硫氰酸酶会失活。这一发现表明存在硫氰酸酶失活的连锁反应型机制。
