Comparative reactivity of carbamyl phosphate and glucose 6-phosphate with the glucose-6-phosphatase of intact microsomes.
The ability of glucose 6-phosphate and carbamyl phosphate to serve as substrates for glucose-6-phosphatase (D-glucose-6-phosphate phosphohydrolase; EC 3.1.3.9) of intact and disrupted microsomes from rat liver was compared at pH 7.0. Results support carbamyl phosphate and glucose 6-phosphate as effective substrates with both. Km values for carbamyl phosphate and glucose 6-phosphate were greater with intact than with disrupted microsomes, but Vmax values were higher with the latter. The substrate translocase-catalytic unit concept of glucose-6-phosphatase function is thus confirmed. The Km values for 3-O-methyl-D-glucose and D-glucose were larger when determined with intact than with disrupted microsomes. This observation is consistent with the involvement of a translocase specific for hexose substrate as a rate-influencing determinant in phosphotransferase activity of glucose-6-phosphatase.
D019325:3-O-Methylglucose; D000818:Animals; D002219:Carbamates / Q000378:metabolism*; D002221:Carbamyl Phosphate / Q000378:metabolism*; D002458:Cell Fractionation; D005952:Glucose-6-Phosphatase / Q000378:metabolism*; D019298:Glucose-6-Phosphate; D005958:Glucosephosphates / Q000378:metabolism*; D007700:Kinetics; D008757:Methylglucosides / Q000378:metabolism; D008862:Microsomes, Liver / Q000201:enzymology*; D051381:Rats; D013379:Substrate Specificity
D002219:Carbamates; D005958:Glucosephosphates; D008757:Methylglucosides; D019325:3-O-Methylglucose; D019298:Glucose-6-Phosphate; D002221:Carbamyl Phosphate; D005952:Glucose-6-Phosphatase