Bosron W F, Crabb D W, Li T K
Pharmacol Biochem Behav. 1983;18 Suppl 1:223-7. doi: 10.1016/0091-3057(83)90175-2.
Since alcohol dehydrogenase (ADH) catalyzes the rate-limiting step for ethanol metabolism, knowledge of the steady-state kinetics of ADH in liver is fundamental to the understanding of the pharmacokinetics of ethanol elimination. Accordingly, we have determined the kinetic properties of purified ADH isoenzymes in rat and human liver. At low ethanol concentrations, rat liver ADH obeys the Theorell-Chance mechanism and the equation predicts that activity in vivo is limited below Vmax mainly by NADH inhibition. At ethanol concentrations above 10 mM, substrate inhibition, consistent with the formation a dead-end ADH-NADH-ethanol complex, also becomes a rate-limiting factor. ADH activity, calculated from this equation and the concentrations of substrates and products present in liver during ethanol oxidation, agrees well with ethanol elimination rates measured in vivo. With human liver ADH, large differences are observed in the kinetic properties of 5 homodimeric isoenzymes: gamma 1 gamma 1 and gamma 2 gamma 2 exhibit negative cooperativity for ethanol saturation, while alpha alpha, beta 1 beta 1 and beta ind beta ind obey Michaelis-Menten kinetics. At pH 7.5, Km values for ethanol and Vmax values range 0.048 mM and 9 min-1 for beta 1 beta 1 to 64 mM and 560 min-1 for beta ind beta ind, respectively. Therefore, individuals with different ADH phenotypes should display different ethanol elimination profiles.
由于乙醇脱氢酶（ADH）催化乙醇代谢的限速步骤，了解肝脏中ADH的稳态动力学是理解乙醇消除药代动力学的基础。因此，我们已经确定了大鼠和人肝脏中纯化的ADH同工酶的动力学特性。在低乙醇浓度下，大鼠肝脏ADH遵循Theorell-Chance机制，该方程预测体内活性在Vmax以下主要受NADH抑制的限制。在乙醇浓度高于10 mM时，底物抑制（与形成无活性的ADH-NADH-乙醇复合物一致）也成为限速因素。根据该方程以及乙醇氧化过程中肝脏中存在的底物和产物浓度计算出的ADH活性，与体内测得的乙醇消除率非常吻合。对于人肝脏ADH，在5种同二聚体同工酶的动力学特性上观察到很大差异：γ1γ1和γ2γ2对乙醇饱和表现出负协同性，而αα、β1β1和βindβind遵循米氏动力学。在pH 7.5时，乙醇的Km值和Vmax值分别从β1β1的0.048 mM和9 min-1到βindβind的64 mM和560 min-1不等。因此，具有不同ADH表型的个体应表现出不同的乙醇消除曲线。
