TY - JOUR
T1 - Electrostatic and steric contributions to regulation at the active site of isocitrate dehydrogenase
AU - Dean, Antony M.
AU - Koshland, Daniel E.
PY - 1990/8/31
Y1 - 1990/8/31
N2 - The isocitrate dehydrogenase of Escherichia coli is regulated by covalent modification at the active site rather than, as expected, at an allosteric site. As a means of evaluating the mechanism of regulation, the kinetics of the substrate, 2R,3S-isocitrate, and a substrate analog, 2R-malate, were compared for the native, phosphorylated, and mutant enzymes. Phosphorylation decreases activity by more than a factor of 106 for the true substrate, but causes minor changes in the activity of the substrate analog. The kinetic results indicate that electrostatic repulsion and steric hindrance between the phosphoryl moiety and the γ carboxyl group of 2R,3S-isocitrate are the major causes of the inactivation, with a lesser contribution from the loss of a hydrogen bond.
AB - The isocitrate dehydrogenase of Escherichia coli is regulated by covalent modification at the active site rather than, as expected, at an allosteric site. As a means of evaluating the mechanism of regulation, the kinetics of the substrate, 2R,3S-isocitrate, and a substrate analog, 2R-malate, were compared for the native, phosphorylated, and mutant enzymes. Phosphorylation decreases activity by more than a factor of 106 for the true substrate, but causes minor changes in the activity of the substrate analog. The kinetic results indicate that electrostatic repulsion and steric hindrance between the phosphoryl moiety and the γ carboxyl group of 2R,3S-isocitrate are the major causes of the inactivation, with a lesser contribution from the loss of a hydrogen bond.
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M3 - Article
C2 - 2204110
AN - SCOPUS:0025002460
SN - 0036-8075
VL - 249
SP - 1044
EP - 1046
JO - Science
JF - Science
IS - 4972
ER -