JBC, Vol. 250, Issue 15, 945-950, Aug, 1975
Phosphoenolpyruvate hydrolase activity of rabbit muscle pyruvate kinase
K. Erhard and R. C. Davis
Rabbit muscle pyruvate kinase catalyzes the hydrolysis of P-enolpyruvate at
the same active site which catalyzes the physiologically important kinase
reaction. The hydrolase activity is lower than the kinase activity by a
factor of at least 10(3). There are specific monovalent cation and divalent
cation requirements. No other cofactors are required. The relative
activation of the pyruvate kinase for the hydrolase reaction is: Ni(II)
greater than Co(II) greater than Mg(II) greater than Mn(II). This parallels
the rates of nonenzymatic hydrolysis of P-enolpyruvate (Benkovic, S.J., and
Schray, K.J. (1968) Biochemistry 7, 4097-4102). The pH rate profiles of the
hydrolase and kinase reactions activated by Ni(II) and Co(II) are similar,
suggesting common features in their mechanisms. In contrast to the kinase
reaction, the reaction velocity of the hydrolase increases at high Co(II)
concentrations indicating a second mode for hydrolysis.