title: Effects of Ca2+ and V5+ on glucose-6-phosphatase activity in rat liver microsomes: the Ca2+ effect is reversed by regucalcin.
abstract: The effect of regucalcin, a calcium-binding protein isolated from rat liver cytosol, on glucose-6-phosphatase in the microsomes of rat liver was investigated. Addition of Ca2+ up to 2.5 microM to the enzyme reaction mixture caused a significant increase of glucose-6-phosphatase activity in hepatic microsomes, while Ni2+, Zn2+, Cd2+, Cu2+, Mn2+ and Co2+ (20 microM) did not have an appreciable effect. Vanadate (V5+) markedly inhibited the enzyme activity; a significant inhibitory effect was seen at 10 microM V5+. The Ca2+-induced increase of glucose-6-phosphatase activity was reversed by the presence of regucalcin; the effect was complete at 1.0 microM of the protein. Regucalcium had no effect on the basal activity of the enzyme. Meanwhile, the inhibitory effect of V5+ (10-100 microM) on glucose-6-phosphatase was not appreciably blocked by the presence of regucalcin (up to 2.0 microM). The present data suggest that hepatic microsomal glucose-6-phosphatase is uniquely regulated by Ca2+ and V5+, of various metals, and that the Ca2+ effect is reversed by regucalcin. The present study supports the view that regucalcin plays an important role as a regulatory protein in liver cell function related to Ca2+.
authors.forename: M
authors.initials: M
authors.lastname: Yamaguchi
authors.forename: S
authors.initials: S
authors.lastname: Mori
authors.forename: Y
authors.initials: Y
authors.lastname: Suketa
mesh_terms: D000818:Animals; D002118:Calcium / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002135:Calcium-Binding Proteins / Q000502:physiology*; D002265:Carboxylic Ester Hydrolases; D005952:Glucose-6-Phosphatase / Q000037:antagonists & inhibitors*; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D015238:Sulfotransferases; D014638:Vanadates / Q000494:pharmacology*
chemical_list: D002135:Calcium-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D014638:Vanadates; D015238:Sulfotransferases; C028152:alcohol sulfotransferase; D002265:Carboxylic Ester Hydrolases; C513325:Rgn protein, rat; D005952:Glucose-6-Phosphatase; D002118:Calcium