Determination of Liver Microsomal Glucose-6-Phosphatase *

A procedure for the determination of liver microsomal glucose-6-phosphatase is described. Homogenization and ultracentrifrigation were used to prepare a precipitate whose character was defined by monitoring the desired enzyme activity which serves as a marker. Activity of the enzyme was determined by means of a sensitive colorimetric reaction for the product, inorganic phosphate. Non-enzymatic hydrolysis problems with the substrate are minimized in this procedure by the masking action of citrate. The final heteropoly blue color appears to be considerably sensitized by interaction of phosphomolybdous ion with arsenite. The stability of the relatively labile enzyme was ensured by chelating any metals present with ethylene diamine tetraacetic acid. The overall results obtained by the procedure appear to be useful as an aid in the diagnosis of Type I glycogenosis, a glycogen storage disease called Von Gierke’s disease