COENZYME-DEPENDENT ALCOHOL DEHYDROGENASES IN CANDIDA-GUILLIERMONDII Y4

Candida guilliermondii Y4 is capable of synthesizing two different alcohol dehydrogenases. ADH1 is constitutive on different carbon sources under shaking or settling conditions and its activity is prominent on gel electrophoresis. ADH2 is only synthesized under shaking condition. Two types of mutants were isolated using an allyl alcohol selection technique. ADH1-deficient mutants had 2.7% ADH activity of the wild type, while ADH2-deficient mutants had an ADH activity as high as that of the wild-type ADH activity. The alcohol dehydrogenases of the mutants differ from those of the wild type in their relative oxidation rates of alcohols. ADH1 appears to possess a functional role mainly in the production of ethanol from acetaldehyde, while ADH2 functions mainly in the oxidation of ethanol to acetaldehyde. However, both enzymes seem to be capable of carrying out the reverse reactions, since mutants lacking either of them still grew satisfactorily on different carbon sources.