Studies of the effects of phenylalanine and pH on pyruvate kinase from the muscle of the sea mollusc Concholepas concholepas

Abstract

1. 1. Muscle pyruvate kinase from the mollusc Concholepas concholepas shows slight sigmoidal kinetics with phosphoenolpyruvate as substrate. The enzyme is strongly inhibited by phenylalanine. 2. 2. At low phosphoenolpyruvate concentrations, F1,6-P 2 enhances the enzyme activity. F1,6-P 2 is also able to overcome the inhibitory action by phenylalanine. 3. 3. The kinetic properties of the enzyme are independent of pH between 7.0 and 8.0 and unchanged after preincubation for 30 min at temperatures between 21 and 40°C. 4. 4. It is suggested that the levels of both phenylalanine and F1,6-P 2 would be important in the control of pyruvate kinase in vivo.