Eisses K T, Schoonen W G, Aben W, Scharloo W, Thörig G E
Mol Gen Genet. 1985;199(1):76-81. doi: 10.1007/BF00327513.
Until recently the alcohol dehydrogenase of Drosophila melanogaster was thought to act only in the first step of primary alcohol oxidation, producing an aldehyde. Instead, acetic acid is the main product of a two-step process. A rapid procedure was developed for the isolation and purification of two allozymes. The thermostability of the purified enzymes was found to be very different, t 1/2 at 35 degrees C, being 45 min and 130 min for ADH-F and ADH-71k respectively. The kinetic parameters of ethanol oxidation by the two purified allozymes were determined within physiological substrate and coenzyme ranges. The use of artificial electron acceptors has a notable influence on the ethanol oxidation: the apparent Michaelis constants increase; the oxidation rate with ADH-71k increases, whereas it decreases with ADH-F. Purified ADH is shown to be able to catalyze the oxidation of acetaldehyde solely in the presence of NAD+, and PMS and MTT as artificial electron acceptors. From the kinetic data the relative in vivo oxidation rates of ethanol by both ADH allozymes were calculated. ADH-F turned out to be somewhat less effective (30%-40%) than ADH-71k. The physiological consequences of these differences are discussed.
直到最近，人们还认为黑腹果蝇的乙醇脱氢酶仅在伯醇氧化的第一步起作用，生成醛。相反，乙酸是一个两步过程的主要产物。开发了一种快速程序用于两种同工酶的分离和纯化。发现纯化酶的热稳定性差异很大，在35℃下，ADH-F和ADH-71k的半衰期分别为45分钟和130分钟。在生理底物和辅酶范围内测定了两种纯化同工酶氧化乙醇的动力学参数。使用人工电子受体对乙醇氧化有显著影响：表观米氏常数增加；ADH-71k的氧化速率增加，而ADH-F的氧化速率降低。纯化的ADH仅在存在NAD+以及作为人工电子受体的PMS和MTT时，才能催化乙醛的氧化。根据动力学数据计算了两种ADH同工酶在体内乙醇的相对氧化速率。结果表明，ADH-F的效率比ADH-71k略低（30%-40%）。讨论了这些差异的生理后果。
