The nature of modifications by various anions of synthetic and hydrolytic activities of multifunctional glucose-6-phosphatase

Colilla, William; Johnson, W. Thomas; Nordlie, Robert C.

doi:10.1016/0005-2744(74)90134-x

Cited by 13 publications

(3 citation statements)

References 26 publications

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“…And even if dianions inhibit more effectively than monoanionic or neutral species, the latter clearly are not precluded as inhibitors a t the glucose-6-P binding site o r elsewhere. This is evident from the inhibition found for one tri-and two di-alkyl phosphates at p H 7.5, from other reports of monoanionic competitive inhibitors ( 13,19,22,33 ), from the finding that diphenyl phosphate was as effective an inhibitor as monophenyl phosphate, and from reports of neutral noncompetitive o r mixed-type inhibitors of this enzyme (10, 13, 2 9 ) . Furthermore, in preliminary studies we have found that certain nonionic organophosphorus (and carbamate) pesticides inhibit glucose-6-phosphatase activity (unpublished observations).…”

Section: Resultsmentioning

confidence: 65%

Inhibition by orthophosphate esters of glucose-6-phosphatase

Walls¹,

Lygre²

1980

Can. J. Biochem.

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Inhibition of rat liver microsomal glucose-6-phosphatase (D-glucose-6-phosphate phosphohydrolase, EC 3.1.3.9) by orthophosphate and organophosphate esters was examined at pH 6.0 and 7.5 with and without enzyme pretreatment with 0.2% (w/v) deoxycholate. Inhibition by orthophosphate and monoethyl phosphate was competitive with respect to glucose-6-P while inhibition by mono- and di-phenyl phosphate was of the mixed type. Monoalkyl phosphates were more effective inhibitors than the analogous di- and tri-alkyl phosphates and deoxycholate potentiated the inhibitory effects. Mono- and di-phenyl phosphates were more effective inhibitors than triphenyl phosphate, and deoxycholate decreased these inhibitory effects. The results are interpreted in terms of inhibitor and deoxycholate interactions with the enzyme.

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Section: Resultsmentioning

confidence: 65%

Inhibition by orthophosphate esters of glucose-6-phosphatase

Walls¹,

Lygre²

1980

Can. J. Biochem.

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“…A parallel increase selectively in the biosynthetic function of the glucose-6-phosphatase involving these same factors recently has been reported by the present authors (90,91). Although changes in osmolarity do not directly impact the glucose-6-phosphatase system (90, 9 l), C1-does inhibit (92). Most importantly here, the reduction in cellular C1from a concentration of 30-50 mM to one of 10-20 mM, as was shown to lead to an increased glycogen synthase a (89), also deinhibited significantly carbamyl-P:glucose phosphotransferase, but not glucose-6-P phosphohydrolase, activity of the liver microsomal glucose-6-phosphatase system (90,91).…”

Section: Recent Experimental Evidence In Support Of High-andglucose Ementioning

confidence: 99%

Glucose-6-Phosphatase Structure, Regulation, and Function: An Update

Foster¹,

Pederson²,

Nordlie³

1997

Experimental Biology and Medicine

106

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Work on the glucose-6-phosphatase system has intensified and diversified extensively in the past 3 years. The gene for the catalytic unit of the liver enzyme has been cloned from three species, and regulation at the level of gene expression is being studied in several laboratories worldwide. More than 20 sites of mutation in the catalytic unit protein have been demonstrated to underlie glycogenesis type 1a. inhibition of glucose-6-P hydrolysis by several newly identified competitive and time-dependent, irreversible inhibitors has been demonstrated and in several instances the predicted effects on liver glycogen formation and/or breakdown and on blood glucose production have been shown. Refinements in and additions to the presently dominant "substrate transport-catalytic unit" topological model for the glucose-6-phosphatase system have been made. A new model alternative to this, based on the "combined conformational flexibility-substrate transport" concept, has emerged. Experimental evidence for the phosphorylation of glucose in liver by high-K(m),glucose enzyme(s) in addition to glucokinase has continued to emerge, and new in vitro evidence supportive of biosynthetic functions of the glucose-6-phosphatase system in this role has appeared. High levels of multifunctional glucose-6-phosphatase have been shown present in pancreatic islet beta cells. Glucose-6-P has been established as the likely insulin secretagog in beta cells. Interesting differences in the temporal responses of glucose-6-phosphatase in kidney and liver have been demonstrated. An initial attempt is made here to meld the hepatic and pancreatic islet beta-cell glucose-6-phosphatase systems, and to a lesser extent the kidney tubular and small intestinal mucosal glucose-6-phosphatase systems into an integrated, coordinated mechanism involved in whole-body glucose homeostasis in health and disease.

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“…Unfortunately, the most likely reason why Giroix et al (1987) found no glucose-6-phosphatase system in rat islets is that they had completely inactivated it. They cultured the islet cells and then sonicated them (sonication inactivates glucose-6-phosphatase enzyme) in the presence of 150 mM-Cl-, which inhibits the glucose-6phosphatase enzyme (Colilla et al, 1974). In addition, Vol.…”

Section: Glucose-6-phosphatase Activitymentioning

confidence: 99%