Molecular weight of microsomal glucose-6-phosphatase of rat and human liver

Abstract

Salt-washed and unwashed and aluminum oxide treated microsomes of human liver, and washed microsomes of liver of normally fed, 1 day fasted and alloxan diabetic rats were subjected to polyacrylamide gel electrophoresis in presence of sodium dodecylsulfate and urea. Unwashed and aluminum oxide treated microsomes showed several protein bands, but salt-washed microsomes gave only one major protein band. This major protein band which appeared in all the preparations showed glucose-6- P activity on incubation of the electrophoresed gel with the substrate and subsequent staining with ammonium sulfide. Molecular weight of this protein was estimated to be 63,000 ± 6,800. Glucose-6- P and pyrophosphatase activities were measured after subjecting lyophilized microsomes, aluminum oxide treated supernatant and residue fractions of human and rat liver to ionizing radiation in vacuo at different doses (Mrads). There was no significant difference between either the surviving fraction of glucose-6- P and pyrophosphatase activities or among the different preparations of human and rat liver at a given radiation dose. Computer analysis of the pooled data gave a value of 9.16 Mrads for 37% survival of the activity which corresponds to a molecular weight of 70,000.