Activation of rat-liver microsomal glucose 6-phosphatase, inorganic pyrophosphatase and inorganic pyrophosphate-glucose phosphotransferase by hydroxyl ion.

Abstract

Abstract 1. 1. OH- has been shown to produce a 2- to 3-fold increase in the apparent activity in vitro of rat-liver microsomal glucose 6-phosphatase (EC 3.1.3.9) and the related enzymatic activities, inorganic pyrophosphatase, inorganic pyrophosphate-glucose phosphotransferase and adenosine-5′-triphosphate-glucose phosphotransferase. 2. 2. Optimal activation is achieved by pre-treatment of liver microsomes with ammonium or amino acid buffers at pH 9.5–9.8. Inactivation is observed above pH 10. 3. 3. This activation is as great or greater than that produced by deoxycholate or Triton X-100 treatment and the thermal instability introduced by these reagents is avoided. 4. 4. Alteration of the microsomal membranes by treatment with base is accompanied by a decrease in turbidity but does not result in a solubilization of the enzyme. The essential protein-lipid binding is apparently retained and the enzyme, so treated, is relatively stable at 30°. 5. 5. NH4OH pretreatment of microsomes results in a lowering of the apparent Michaelis constant for glucose 6-phosphatase, similar to that caused by digitonin, deoxycholate and Triton X-100.