Effects of 3-mercaptopicolinic acid and a derivative of chlorogenic acid (S-3483) on hepatic and islet glucose-6-phosphatase activity

Glucose-6-phosphatase activity was measured in hepatic microsomes and in pancreatic islets from ob/ob mice. In hepatic microsomes vanadate, phlorizin, 3-mercaptopicolinic acid and a derivative of chlorogenic acid (S-3483) inhibited the translocase activity of the enzyme, vanadate in addition inhibited hydrolase activity. In islets, vanadate inhibited both components of the enzyme, phlorizin inhibited only hydrolase activity while 3-mercaptopicolinic acid and compound S-3483 were without effect. Similarly, when islets were incubated with (H2O)-H-3 and unlabeled glucose, the incorporation of' H-3 into medium glucose was inhibited by vanadate and phlorizin, but not by 3-mercaptopicolinic acid and S-3483. These findings suggest that, as with glucokinase, different isoenzymes of glucose-6-phosphatase are present in islets and liver. (C) 1998 Elsevier Science B.V. All rights reserved.