Favilla R, Cavatorta P, Mazzini A, Fava A
Eur J Biochem. 1980 Feb;104(1):223-7. doi: 10.1111/j.1432-1033.1980.tb04419.x.
The results of steady-state kinetic measurements on the initial rate of the peroxidatic reaction between beta-NAD+ and hydrogen peroxide, catalyzed by horse liver alcohol dehydrogenase, at pH 7 are described. A simple sequential mechanism is deduced from graphical analysis of the data plotted according to Eadie-Augustinsson-Hofstee primary plots and the values of the true kinetic parameters KmNAD, KmH2O2 and V are estimated from the corresponding secondary plots. Ethanol has been found to compete with hydrogen peroxide for the same enzyme active site. During the catalytic process a progressive inactivation of the enzyme occurs caused by H2O2. The rate law of this process is quantitatively described at pH 7 both in the absence and in the presence of NAD+. The coenzyme has been found to protect the enzyme against inactivation by H2O2, which oxidized essential cysteine residues. The results obtained from the study of both catalytic and inactivating processes are finally rationalized on the basis of a general mechanistic scheme.
本文描述了在pH 7条件下，马肝醇脱氢酶催化β-NAD⁺与过氧化氢之间过氧化物酶反应初始速率的稳态动力学测量结果。根据Eadie-Augustinsson-Hofstee原始图绘制的数据进行图形分析，推导出一个简单的顺序机制，并从相应的二级图中估计出真实动力学参数KmNAD、KmH₂O₂和V的值。已发现乙醇与过氧化氢竞争同一个酶活性位点。在催化过程中，H₂O₂导致酶逐渐失活。该过程的速率定律在pH 7条件下，无论有无NAD⁺均进行了定量描述。已发现辅酶可保护酶免受H₂O₂的失活作用，H₂O₂会氧化必需的半胱氨酸残基。最后，基于一个通用的机制方案，对催化和失活过程的研究结果进行了合理化分析。
