Characterization of the proteolytic activity firmly attached to yeast phoshoenolpyruvate carboxykinase

Incubation of partially purified yeast phosphoenolpyruvate carboxykinase (ATP:oxaloacetate carboxy-lyase (transphosphorylating), EC 4.1.1.49) with 5% mercaptoethanol and 0.01% sodium dodecyl sulfate at 37 degrees C results in degradation of the enzyme. The degradation can be partially prevented by addition of proteinase B inhibitor 2 or phenylmethylsulfonyl fluoride, an inhibitor of proteinase B and carboxypeptidase Y. The degradation can be completely inhibited by addition of proteinase B inhibitor 2 together with pepstatin, and inhibitor of proteinase A. Thus it appears that proteolytic activities are firmly attached to phosphoenolpyruvate carboxykinase and are identical with the yeast proteinases A and B. The latter conclusion was supported by experiments using the pure yeast proteinases.