Abstract: Glutamate dehydrogenase(GDH) is present mainly in mitochondria in higher plants and catalyses both the amination of a-oxoglutamate, with NADH as the electron donor, and the deamination of glutamate to ammonia and a-oxoglutamate, with NAD+ as the electron receptor. The NAD (H)-GDH, with a molecular weight of 255-258kD, is composed of six subunits of a and b in different ratios to form seven isoenzymes. The enzyme seems to function in assimilation of ammonia under stress conditions such as high temperature, in senescence and other abnormalities. It also functions in higher plants to direct carbon skeletons into the citric acid cycle under conditions of carbon stress.