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Abstract
Asparaginase II activity in Saccharomyces cerevisiae can be derepressed in stationary phase cells by nitrogen starvation in the presence of an energy source. We have found that high activity of this enzyme is present in early-exponential phase cells even in the presence of abundant nitrogen. In growing cells that contain high asparaginase II activity, further derepression by nitrogen results in the rapid appearance of additional activity. Rapid loss of activity occurs as cultures begin to emerge from exponential growth. Synthesis of protein is required just before loss of activity occurs. Supplementing cultures with l-asparagine or l-glutamine strongly affects the kinetics of loss of activity. Mutation in ASP2 or ASP3, which results in inability to derepress this enzyme in stationary phase cells, also prohibits the development of the enzyme in exponentially growing cells.
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