Summary: The soil yeast was grown in continuous culture on a minimal medium containing phenol or glucose, or both. The utilization rate of the carbon substrate and the specific activities of catechol 1,2-dioxygenase (EC, pyruvate kinase (EC, alanine aminotransferase (EC and aspartate aminotransferase (EC were determined. Both substrates were utilized simultaneously, the rate of glucose utilization being much higher than that of phenol. Basal activity of catechol 1,2-dioxygenase [3-5 mU (mg protein)] was found in glucose-grown cells. High glucose concentrations (20 g I) did not prevent the induction of phenol metabolism as reflected in the derepression of catechol 1,2-dioxygenase and the consumption of phenol. However, glucose partially repressed the overall phenol metabolism when was grown on phenol together with glucose: phenol utilization and catechol 1,2-dioxygenase activity were reduced by 60% and 75% respectively. Complete derepression of catechol 1,2-dioxygenase did not occur until the glucose was depleted. Catechol 1,2-dioxygenase was repressed, but not inactivated, by glucose, as judged from the wash-out profile during transition from growth on phenol to growth on glucose. Pyruvate kinase activity was about twice as high in glucose-grown cells as in phenol-grown cells, and the level of the enzyme during growth on glucose was unaffected by the presence of phenol. Aspartate aminotransferase activity was higher in cells grown with phenol, or phenol together with glucose, than in cells grown on glucose alone. Alanine aminotransferase activity increased only when both substrates were present.


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