Schöpp W, Aurich H
Biochem J. 1976 Jul 1;157(1):15-22. doi: 10.1042/bj1570015.
Kinetic studies of yeast alcohol dehydrogenase with NAD+ and ethanol, hexanol or decanol as substrates invariably result in non-linear Lineweaver-Burk plots if the alcohol is the variable substrate. The kinetic coefficients determined from secondary plots are consistent with an 'equilibrium random-order' mechanism for extremely low alcohol concentrations and for all alcohols, the transformation of the ternary complexes being the rate-limiting step of the reaction. This mechanism also applies to long-chain substrates at high concentrations, whereas the rate of the ethanol-NAD+ reaction at high ethanol concentrations is determined by the dissociation of the enzyme-NADH complex. The dissociation constants for the enzyme-NAD+ complex and for the enzyme-alcohol complexes obtained from the kinetic quotients satisfactorily correspond to the dissociation constants obtained by use of other techniques. It is suggested that the non-linear curves may be attributed to a structural change in the enzyme itself, caused by the alcohol.
如果以醇类作为可变底物，用NAD⁺以及乙醇、己醇或癸醇作为底物对酵母乙醇脱氢酶进行动力学研究时，所得的Lineweaver - Burk图总是呈非线性。对于极低的醇浓度以及所有醇类，由二级图确定的动力学系数与“平衡随机顺序”机制一致，三元复合物的转化是反应的限速步骤。该机制也适用于高浓度的长链底物，而在高乙醇浓度下乙醇 - NAD⁺反应的速率由酶 - NADH复合物的解离决定。从动力学商获得的酶 - NAD⁺复合物和酶 - 醇复合物的解离常数与通过其他技术获得的解离常数令人满意地相符。有人认为，非线性曲线可能归因于醇类引起的酶自身结构变化。
