Effects of Yeast Proteinase A, Proteinase B and Carboxypeptidase Y on Yeast Phosphofructokinase

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Abstract
A crude yeast extract containing phosphofructokinase with proteinase A, proteinase B or carboxypeptidase Y was incubated. Proteinase B and carboxypeptidase Y did not change the activity of phosphofructokinase during incubation. Incubation with proteinase A resulted in a 40-100% activation; continued incubation led to an inactivation of the enzyme. Addition of allosteric effectors did not change the activation or inactivation process. The activated phosphofructokinase was not changed with respect to pH optimum and ATP inhibition. Molecular weight determinations of phosphofructokinase in crude extracts in the presence of inhibitors of proteinase A indicated a MW of 700,000. Without inhibitors of proteinase A, the MW was 600,000, while after 40-100% activation by proteinase A, a MW of 500,000 was obtained. The activity profile of proteinase A in density gradients indicated that this enzyme is bound to a variety of cellular proteins.

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