Affiliation:
1. Institut für Mikrobiologie, Technische Hochschule Darmstadt, D-6100 Darmstadt, Federal Republic of Germany
Abstract
Saccharomyces cerevisiae
mutants unable to grow and ferment glucose have been isolated. Of 45 clones isolated, 25 had single enzyme defects of one of the following activities: phosphoglucose isomerase (
pgi
), phosphofructokinase (
pfk
), triosephosphate isomerase (
tpi
), phosphoglycerate kinase (
pgk
), phosphoglyceromutase (
pgm
), and pyruvate kinase (
pyk
). Phosphofructokinase activities in crude extracts of the
pfk
mutant were only 2% of the wild-type level. However, normal growth on glucose medium and normal fermentation of glucose suggested either that the mutant enzyme was considerably more active in vivo or, alternatively, that 2% residual activity was sufficient for normal glycolysis. All other mutants were moderately to strongly inhibited by glucose. Unusually high concentrations of glycolytic metabolites were observed before the reaction catalyzed by the enzyme which was absent in a given mutant strain when incubated on glucose. This confirmed at the cellular level the location of the defect as determined by enzyme assays. With
adh
(lacks all three alcohol dehydrogenase isozymes) and
pgk
mutants, accumulation of the typical levels of hexosephosphates was prevented when respiration was blocked with antimycin A. A typical feature of all glycolytic mutants described here was the rapid depletion of the intracellular adenosine 5′-triphosphate pool after transfer to glucose medium. No correlation of low or high levels of fructose-1,6-bisphosphate with the degree of catabolite repression and inactivation could be found. This observation does not support the concept that hexose metabolites are directly involved in these regulatory mechanisms in yeast.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
155 articles.
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