Activation of microsomal glucose-6-phosphatase and associated pyrophosphatase and pyrophosphate-glucose phosphotransferase activities of human liver by aluminum oxide

A new microtechnique for the analysis of the human hepatic microsomal glucose-6-phosphatase system

A microtechnique has been developed which enables a complete kinetic analysis of the human hepatic microsomal glucose-6-phosphatase system to be carried out in microsomes isolated from very small liver samples. Complete or partial deficiencies of any of the proteins of the glucose-6-phosphatase system resulting in Type 1a, 1b, 1c or 1d glycogen storage disease can be therefore be diagnosed using hepatic needle biopsy samples, whereas previous methods of diagnosis needed large wedge biopsy samples requiring laparotomy.

Glucose-6-phosphatase activity in liver and blood platelets of two patients with glycogen storage disease type I

Glucose-6-phosphatase (G-6-Pase) activity in liver and blood platelets of two patients with glycogen storage disease (GSD) type I is described. Both patients had a reduced activity of G-6-Pase in liver. The km value for glucose 6-phosphate (G-6-P) of residual activity in liver of both patients was similar to that of control liver. We could not demonstrate any reduced activity of platelet G-6-Pase in the patients. Platelet G-6-Pase with our assay method seems to represent a nonspecific phosphatase activity. Our observation suggests that it is necessary to examine platelet G-6-Pase of many other patients with GSD type I to confirm that G-6-Pase deficiency can be diagnosed by enzyme assay performed on blood platelets.

Effect of potassium on human and rat liver glucose-6-phosphatase

Potassium chloride concentrations of 100-150 mM were shown to inhibit (20-40%) human and rat liver microsomal glucose-6-phosphatase when the substrate was reduced to physiological concentration. When the enzyme was solubilized by treatment of microsomes with A12O3 the inhibition could be observed at greater substrate concentrations. Since potassium deprivation is associated with hyperglycemia in both animals and man, these observations may have physiological significance.