CHARACTERIZATION OF PHOSPHOENOLPYRUVATE CARBOXYKINASE FROM CORYNEBACTERIUM-GLUTAMICUM

Phosphoenolpyruvate (PEP) carboxykinase is present in crude extracts o f Corynebacterium glutamicum grown on both glucose and lactate. Prepar ation of PEP carboxykinase free from interfering PEP carboxylase and o xaloacetate decarboxylase showed an absolute dependence on divalent ma nganese and IDP for activity in the oxaloacetate (OAA) formation. Othe r diphosphate nucleotides could not substitute for IDP. The enzyme act ivity displayed Michaelis-Menten kinetics for the substrates PEP, IDP, KHCO3, OAA and ITP with a K(m) of 0.7 mM, 0.4 mM, 12 mM, 1.0 mM, and 0.5 mM, respectively. At the optimum pH of 6.6, 850 nmol of OAA were f ormed per min per mg of protein. ATP inhibited PEP carboxykinase in th e OAA forming reaction for 60% at 0.1 mM, indicating that the enzyme m ainly functions in gluconeogenesis.