Liver Microsomal Glucose 6=Phosphatase, Inorganic Pyrophosphatase, and PyrophosphatsGlucose Phosphotransferase IV. EFFECTS OF ADRENALECTOMY AND CORTISONE ADlMINISTRATION ON ACTIVITIES ASSAYED IN THE ABSENCE AND PRESENCE OF DEOXYCHOLATE*

Levels of liver microsomal glucose 6-phosphatase (Reaction 1) are significantly stimulated in the diabetic or glucocorticoidtreated animal, and they are depressed after insulin administration or adrenalectomy (see, for example, References 1 to 8). This hydrolytic activity may play a physiologically significant role in the regulation of blood glucose and liver glycogen levels (1, 2, 9). Recent studies reported from our laboratory (10, 11) and by Stetten (12) and Stetten and Taft (13) indicate that inorganic pyrophosphate hydrolysis (Reaction 2) and glucose 6-phosphate synthesis via the pyrophosphate-glucose phosphotransferase reaction (Reaction 3) appear to be catalyzed by this same microsomal enzyme. The presence of nucleoside triphosphateand nucleoside diphosphate-glucose phosphotransferase activities (Reactions 4 and 5) in deoxycholate-treated rat liver microsomes and kidney homogenates is documented in Paper III of this series (14). Levels of these microsomal phosphotransferases have been found to rise in alloxan diabetes and to decrease after insulin administration (14).