The hepatic glucose-6-phosphatase system in Ehrlich-ascites-tumour-bearing mice.
To examine the effects of the presence of Ehrlich ascites tumours on both the catalytic unit and the substrate/product translocase components of the glucose-6-phosphatase system in vivo, we isolated microsomes from the livers of control and tumour-bearing mice. Samples were analysed immunochemically for the quantity of catalytic unit, stabilizing protein and translocases T2 and T3 proteins. In comparison experiments, a variety of kinetic studies were performed. The most striking findings in tumour-bearing mice were: a 2.5-fold increase in the quantity of translocase T2 protein; increases in the Km and Vmax. for glucose 6-phosphate phosphohydrolase; and a decrease in the Km value for carbamoyl phosphate (carbamoyl-P) of carbamoyl-P:glucose phosphotransferase, all with intact microsomes. The percentage latency at Vmax. decreased for PPi phosphohydrolase and for glucose 6-phosphate phosphohydrolase, but was unaffected for carbamoyl-P:glucose phosphotransferase. These observations support a tumour-related increase in translocase T2 capacity in vivo, as it transports Pi from the microsomal lumen to the medium and carbamoyl-P or PPi from the medium to the microsomal lumen.
Lucius
R W
RW
Department of Biochemistry and Molecular Biology, Ireland Research Laboratory, University of North Dakota School of Medicine, Grand Forks 58202.
Waddell
I D
ID
Burchell
A
A
Nordlie
R C
RC
D000818:Animals; D017920:Antiporters; D002286:Carcinoma, Ehrlich Tumor / Q000201:enzymology*; D005952:Glucose-6-Phosphatase / Q000378:metabolism*; D007150:Immunohistochemistry; D007700:Kinetics; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D008862:Microsomes, Liver / Q000201:enzymology*; D009004:Monosaccharide Transport Proteins; D010770:Phosphotransferases / Q000378:metabolism
D017920:Antiporters; D009004:Monosaccharide Transport Proteins; C503532:Slc37a4 protein, mouse; C111261:glucose 6-phosphate(transporter); D010770:Phosphotransferases; D005952:Glucose-6-Phosphatase