Turnover of Yeast Fructose‐Bisphosphatase in Different Metabolic Conditions

Earlier work demonstrated that addition of glucose to yeast growing on noncarbohydrate carbon sources sharply reduces the levels of fructose bisphosphatase. This report indicates that the decrease in the levels of fructose bisphosphatase is accompanied by a parallel decrease of cross‐reacting material to specific antibody to fructose bisphosphatase. Use of the specific antibody shows that the loss of activity is irreversible and that its reappearance requires synthesis of protein de novo. The protein is highly stable during growth in ethanol (half life about 90 h). Addition of glucose increases the rate of degradation about 200‐fold. It is shown that the values of the rates of synthesis and degradation of fructose bisphosphatase vary with the metabolic situation of the yeast.