Multiple forms of alcohol dehydrogenase in Saccharomyces cerevisiae

Multiple forms of alcohol dehydrogenase (ADH; E.C. 1.1.1.1.) called ADH-1, -2, -3, and -4 have been demonstrated by starch gel electrophoresis in a haploid strain of Saccharomyces cerevisiae. Two alcohol dehydrogenases, ADH-2 and ADH-4, were purified. The two enzymes can be distinguished from each other by starch gel electrophoresis, substrate specificity, heat stability and Km values for ethanol, acetaldehyde, NAD, and NADH2. ADH-2 oxidizes n-propanol and n-butanol at a faster rate than ethanol. The synthesis of ADH-2 was repressed by glucose. ADH-4, which was identified with the classical yeast alcohol dehydrogenase, was synthesized constitutively. Evidence is presented for the argument that the classical alcohol dehydrogenase functions mainly, during fermentation and ADH-2 participates in formation of carbohydrates from ethanol. The results suggest that ADH-3 is a hybrid form of ADH-2 and ADH-4. The isolation and properties of mutants of S. cerevisiae deficient in one or more forms of alcohol dehydrogenase are described. A mutant, A63-14, deficient in ADH-2 and ADH-3, is shown to produce glycerol at a faster rate than the parent strain. A secondary mutant from A63-14 was isolated in which the synthesis of ADH-2 was less repressible by glucose.