Regulation of glutaminase B in Escherichia coli. II. Modulaltion of activity by carbosylate and borate ions.

Glutaminase B is both activated and inhibited by L-glutamate, the product of the reaction. The activation process is time- and temperature-dependent. Activation by L-glutamate alters the Vmax, So.5, and shape of the substrate saturation curve. The activation decays as a first order process with time after separation of L-glutamate from glutaminase B. L-Glutamate inhibits both glutaminase B and the glutamate-activated enzyme. Like L-glutamate, borate activates and inhibits glutaminase B. Inhibition of the enzyme by glutamine and glutamate analogs is also examined and similarities between the glutamate activation and activation by warming at 23 degrees are noted.