Glutamate-dehydrogenase inactivation by reduced nicotinamide-adenine dinucleotide phosphate

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Abstract
A disproportionate increase in glutamatedehydrogenase activity with increasing concentration of the enzyme has been found, together with a disproportionate decrease in the alanine-dehydrogenase activity of crystalline glutamate dehydrogenase, demonstrating that aggregation influences activity. Rapid induced inactivation of glutamate dehydrogenase by NADPH, which is markedly dependent on salt concentration, pH and temperature, occurs at nearly physiological conditions: The preparations inactivated by NADPH exhibit less stability to denaturation by urea and digestion by trypsin. The inactivation by NADPH is remarkably potentiated by diethylstilboestrol and there is parallel inactivation of the crystalline glutamate dehydrogenase for both glutamate-and alanine-dehydrogenase activities. An increase in titratable SH groups and a change in rotatory power from dextro to laevo follows inactivation of glutamate dehydrogenase by NADPH.