[Binding by glutamate dehydrogenase of 14C from bicarbonate buffer]

Different levels of carbon dioxide (10,20, 40, 80, mM) at pH 6.7, 7.3, 7.6 and 8.5 of incubation media were studied for their effect on the intensity of binding of 14C from bicarbonate buffer by crystalline NAD(P)+-dependent glutamate dehydrogenase from the bovine liver. The effect of a variety of substrates and effectors on this process is investigated. The intensity of the radioactive label binding is shown to increase with pH of the incubation medium and carbon dioxide concentration in it. When acidifying the medium (up to pH 6.5) the enzyme under study does not bind 14C. The preincubation of the enzyme with pyridoxal-5-phosphate decreases considerably the intensity of the label binding with the protein. On the basis of these data a conclusion is drawn about the interaction of CO2 with free amino groups of the enzyme molecule by the type of the carbamate formation. GTP and NADH inhibit this process as well.