Factors affecting the level and activity of pyruvate kinase from Coprinus lagopus sensu Buller.

The specific activity of Coprinus lagopus pyruvate kinase is high under conditions of glycolysis but low under conditions of gluconeogenesis. Only a single form of the enzyme was detectable, the properties of which resemble in a number of respects those of the allosteric forms of pyruvate kinase. These properties include co-operative interactions with phosphoenolpyruvate (PEP), ATP and fructose I ,6-diphospate. Fructose I ,6-diphosphate (FDP) almost completely reverses the inhibitory effects of ATP. The decrease in substrate co-operativity in the presence of FDP, the allosteric activator and the increase in ATP co-operativity in the presence of activator suggests the enzyme can be classed as a ‘K-system’ allosteric protein. The regulatory properties of Coprinus Zagopus pyruvate kinase (ATP-pyruvate phosphotransferase, EC 2.7. I .40) are discussed in relation to differences in allosteric pyruvate kinases from other sources.