title: Differential sensitivities to glucose and galactose repression of gluconeogenic and respiratory enzymes from Saccharomyces cerevisiae.
abstract: The synthesis of isocitrate lyase was induced by the presence of ethanol in the chemostat reaching a specific activity of 200 mU X mg-1 at this induced state. In glucose-limited, derepressed cells, 20 mU X mg-1 were detected and under repressed conditions isocitrate lyase activity was not detected. The sensitivity of gluconeogenic enzymes: cytoplasmic malate dehydrogenase; fructose 1,6-bisphosphatase and isocitrate lyase as well as the mitochondrial enzymes NADH dehydrogenase and succinate cytochrome c oxidase to glucose and galactose repression were studied in chemostat cultures. Our results show that galactose was less effective as a repressor than glucose. Malate dehydrogenase was completely inactivated by glucose, whereas galactose only produced a 78% decrease of specific activity. Fructose 1,6-bisphosphatase and isocitrate lyase were completely inactivated by both sugars but at different rate. Glucose produced an 85% decrease of specific activity of the mitochondrial enzymes whereas galactose only decrease an 67%.
mesh_terms: D003470:Culture Media; D004790:Enzyme Induction; D004794:Enzyme Repression; D000431:Ethanol / Q000032:analysis; D006597:Fructose-Bisphosphatase / Q000096:biosynthesis; D005690:Galactose / Q000494:pharmacology*; D005943:Gluconeogenesis; D005947:Glucose / Q000494:pharmacology*; D007522:Isocitrate Lyase / Q000096:biosynthesis*; D008291:Malate Dehydrogenase / Q000096:biosynthesis; D008928:Mitochondria / Q000201:enzymology; D009245:NADH Dehydrogenase / Q000096:biosynthesis; D007652:Oxo-Acid-Lyases / Q000096:biosynthesis*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013384:Succinate Cytochrome c Oxidoreductase / Q000096:biosynthesis
chemical_list: D003470:Culture Media; D000431:Ethanol; D013384:Succinate Cytochrome c Oxidoreductase; D008291:Malate Dehydrogenase; D009245:NADH Dehydrogenase; D006597:Fructose-Bisphosphatase; D007652:Oxo-Acid-Lyases; D007522:Isocitrate Lyase; D005947:Glucose; D005690:Galactose