アノイリナーゼIIの酵素化学的研究 : (IV)二次酵素反応の理論的検討

概要

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It was been reported that thiaminase II catalizes the second-order reaction. The general kinetics of the reaction, A+B→products, were therefore studied. The basic rate-equation in this study was that intoduced by Dixon and Webb, in which almost no enzymatic reaction was assumed. Though the equation was very complicated, it seemed pertinent to explain actual enzymatic reactions. Applications of this equation from its theoretical basis were discussed in this paper. The second-order enzymatic reactions were classified into the following three types : linear type, substrate-activating type and substrate-inhibitory type. These types are resulted from the modes of steady state of the reaction. In "linear steady state", EAB ternary complex is formed through EA and EB at random sequence. The reaction follows Michaelis-like relation. The types showing phenomena of both substrate-activation and substrate-inhibition are caused by "cyclic steady state". Assuming a cyclic sequence of enzymesubstrate-complex-formation in steady state as E→EA→EAB→EB→(E), the equation suggests that the reaction is activated by substrate A and is inhibited by substrate B. Methods for the determination of both the maximum velocity and the dissociating constant of EAB ternary complex were also discussed.
日本ビタミン学会の論文
1963-06-25