THE SACCHAROMYCES-CEREVISIAE ACETYL-COENZYME-A SYNTHETASE ENCODED BY THE ACS1 GENE, BUT NOT THE ACS2-ENCODED ENZYME, IS SUBJECT TO GLUCOSE CATABOLITE INACTIVATION

In Saccharomyces cerevisiae, the structural genes ACS1 and ACS2 each e ncode an isoenzyme of acetyl-CoA synthetase (ACS; EC 6.2.1.1). Involve ment of glucose catabolite repression in regulation of the two isoenzy mes was investigated by following ACS activity after glucose pulses (1 00 mM) to ethanol-limited chemostat cultures. In wild-type S. cerevisi ae and in an isogenic strain in which ACS2 had been disrupted, ACS act ivity decreased after a glucose pulse. No such inactivation was observ ed in a strain in which ACS1 was disrupted. Western blots demonstrated that the ACS1 product, but not the ACS2 product, was degraded after a glucose pulse. Inactivation kinetics of the ACS1 product resembled th ose of isocitrate lyase.