SOME PROPERTIES OF AN ALCOHOL-DEHYDROGENASE PARTIALLY PURIFIED FROM BAKERS-YEAST GROWN WITHOUT ADDED ZINC

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.