Glutamine synthetase : II. The intracellular localization in the rat liver

Abstract

The intracellular distribution of glutamine synthetase (-glutamate: ammonia ligase (ADP), EC 6.3.1.2) in normal and regenerating rat livers has been studied. The distribution of the enzyme activity in liver in these two situations is similar. The highest enzyme activity occurred in the microsome fraction, which comprised about one half of the activity in liver. Although most of the enzyme activity was identified with the particulate fractions, most of the free glutamine in liver was found in the soluble fraction.In the microsome fraction, the enzyme was associated with the vesicles, and the ribonucleoprotein particles contained no significant activity. NaCl in concentrations less than that of physiological saline caused solubilization of the enzyme from the vesicles. The evidence indicates that the enzyme was attached to the outer surface of the vesicular membrane in the microsome fraction, and that it was probably attached also to the surface of the nuclear and mitochondrial membranes.