Mutational analysis of malate pathways in Schizosaccharomyces pombe

Schizosaccharomyces pombe is of interest to wine-makers because, unlike the Saccharomyces cerevisiae wine yeasts, it efficiently metabolizes all level s of malic acid found in grape musts. To determine the metabolic pathway fo r malate metabolism in Sch. pombe, a mutational analysis was performed usin g a selection system which isolated 154 mutants that were unable to utilize malic acid. The mutants were in three complementation groups which corresp onded to alleles and activities for malate dehydrogenase, malic enzyme and malate transport respectively. Under anaerobic conditions Sch. pombe fermen ts malic acid by using a malate transport, malic enzyme, pyruvate decarboxy lase, alcohol dehydrogenase pathway (a malo-ethanolic fermentation) but und er aerobic conditions malate is both fermented to ethanol and to a much les ser extent, respired as a TCA cycle intermediate. Alleles were mapped genet ically and the locations were confirmed by chromoblotting. Malic enzyme and malate transport alleles were cloned by complementation and the proteins h ave been purified and partially characterized. (C) 1998 Canadian Institute of Food Science and Technology. Published by Elsevier Science Ltd. All righ ts reserved.