米根霉乙醇脱氢酶粗酶液的特性研究

Properties of Alcohol Dehydrogenase (ADH) Preparation from Rhizopus oryzae

米根霉细胞中乙醇脱氢酶(ADH)催化丙酮酸向乙醇支路的转化,导致丙酮酸向乳酸转化通量减少,降低了乳酸转化率。本文初步从米根霉菌丝体中提取制备ADH粗酶液,并研究其酶学特性,结果表明,ADH粗酶液体系反应的最适温度为25℃,温度高于30℃将降低ADH活力。ADH催化体系pH值对其活力有很大影响,最适pH值在7.5左右,高于或低于此值,反应速度均很快下降。在反应体系中添加0.1μmol的EDTA、Mg2+、Ca2+或Zn2+,对该酶都有一定的抑制作用。ADH以乙醛为底物的米氏常数Km为6.90×10-4mol/L。

Alcohol dehydrogenase （ADH） ofRhizopus oryzae is a kind of intracellular enzyme, it catalyzes the transformation of pyruvate to ethanol, which resulting in a decrease of pyruvate flux to target product of L-lactic acid. In this study, the crude ADH preparation was obtained from mycelium ofRhizopus oryzae As 3.3461 and its properties were investigated. The results indicated that the optimum reaction temperature of ADH is 25℃, its activity decreased rapidly when temperature was above 30℃. The pH value of reaction solution also had a marked influence on ADH activity, the optimum pH was 7.5. Addition of Lumol EDTA, Mg^2＋, Ca^2＋ or Zn^2＋ to reaction solution could reduce the activity of ADH. The Kn constant of ADH based on the substrata of acetaldehyde was 6.90× 10^-4mol/L.