Some properties of an alcohol dehydrogenase partially purified from baker's yeast grown without added zinc

Abstract

Alcohol dehydrogenase was partially purified from yeast (Saccharomyces cerevisiae) grown in the presence of 20 .mu.M-MnSO4 without added An2+ and from yeast grown in the presence of 1.8 .mu.M-MnSO4 and 15 .mu.M-ZnSO4. The enzyme from yeast grown with added Zn2+ has the same properties as the crystalline enzyme from commercial supplies of baker''s yeast. The enzyme from yeast grown without added An2+ has quite different properties. It has a mol. wt. [molecular weight] in the region of 72,000 and an s20,w of 5.8S. The values can be compared with a mol.wt. of 141,000 and an s20,w of 7.6S for the crystalline enzyme. ADP-ribose, a common impurity in commercial samples of NAD+, is a potent competitive inhibitor of the new enzyme (Ki = 0.5 .mu.M), but is not so for the crystalline enzyme. The observed maximum rate of ethanol oxidation at p 7.05 and 25.degree. C was decreased 12-fold by the presence of 0.06 mol of inhibitor/mol of NAD+ when using the enzyme from Zn2+-deficient yeast, but with crystalline enzyme the maximum rate was essentiallyu unchanged by this concentration of inhibitor. The kinetic characteristics for the 2 enzymes with ethanol, butan-1-o1, acetaldehyde and butyraldehyde as substrates are markedly different. These kinetic defferences are discussed in relation to the mechanism of catalysis for the enzyme from Zn2+-deficient yeast.