A kinetic study of the pH effect on the allosteric properties of pyruvate kinase from Phycomyces blakesleeanus.
This paper reports the pH-dependence of the allosteric kinetics of Phycomyces blakeseeanus pyruvate kinase with phosphoenol pyruvate and Mg2+ ions in the presence and in the absence of fructose 1,6-bisphosphate (allosteric activator) and L-alanine (allosteric inhibitor). Hydrogen ions increase the affinity of the inhibitory binding sites for phosphoenol pyruvate and Mg2+ ions. Assuming partial conformational states of high and low affinity for inhibitory binding sites, the data presented are in good agreement with the predictions postulated by the two-state concerted-symmetry model of Monod, Wyman, and Changeux. Fructose-1,6-bisphosphate and L-alanine show opposite effects on the interactions of phosphoenol pyruvate and Mg2+ ions with their respective catalytic and inhibitory binding sites. At pH 6.0, the regulation of the Phycomyces pyruvate kinase activity by the concentrations of phosphoenol pyruvate and Mg2+ ions is controlled mainly by L-alanine.
de Arriaga
D
D
Departmento de Bioqúimica y Biologia Molecular, Universidad de León, Spain.
Busto
F
F
del Valle
P
P
Soler
J
J
D000409:Alanine / Q000378:metabolism; D000495:Allosteric Site; D005635:Fructosediphosphates / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D009090:Mucorales / Q000201:enzymology*; D010728:Phosphoenolpyruvate / Q000378:metabolism; D010800:Phycomyces / Q000201:enzymology*; D011770:Pyruvate Kinase / Q000378:metabolism*
D005635:Fructosediphosphates; D010728:Phosphoenolpyruvate; D011770:Pyruvate Kinase; D008274:Magnesium; C029063:fructose-1,6-diphosphate; D000409:Alanine