Carbamyl phosphate: Glucose phosphotransferase activity of hepatic microsomal glucose 6-phosphatase at physiological pH

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Evidence is presented indicating that classical hepatic microsomal D-glucose 6-phosphate phosphohydrolase (EC 3.1.3.9) possesses potent carbamyl phosphate: glucose phosphotransferase activity. Unlike phosphotransferase activity of this enzyme observed with nucleotides, phosphoenolpyruvate, or to a less pronounced extent inorganic pyrophosphate as phosphoryl donors, activity with carbamyl phosphate remains high even at pH 7.0 and 7.5. For example, at the latter pH in the presence of deoxycholate glucose 6-phosphate production with 10 mM carbamyl phosphate and 180 mM D-glucose is approximately double the rate of hydrolysis of 10 mM glucose 6-phosphate. A physiologically significant synthetic role for this phosphotransferase is suggested.