Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.9 (glucose-6-phosphatase)
 3,081 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mechanism of activation of hepatic microsomal glucose-6-phosphatase (EC 3.1.3.9) by histone 2A has been investigated in both intact and disrupted microsomes. Histone 2A increased the Vmax and decreased the Km of glucose-6-phosphatase in intact microsomes but had no effect on glucose-6-phosphatase activity in disrupted microsomes. Histone 2A was shown to activate glucose-6-phosphatase in intact microsomes by disrupting the membrane vesicles and thereby allowing the direct measurement of the activity of the latent glucose-6-phosphatase enzyme. The study demonstrated that disrupting microsomes with histone 2A is an excellent method for directly assaying glucose-6-phosphatase activity as it poses none of the problems encountered with all of the previously used methods.
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PMID:The mechanism of histone activation of the hepatic microsomal glucose-6-phosphatase system: a novel method to assay glucose-6-phosphatase activity. 282 74

The effects of histone 2A and some polycations on microsomal carbamylphosphate:D-glucose phosphotransferase and glucose-6-phosphate phosphohydrolase activities (D-glucose-6-phosphate phosphohydrolase, EC 3.1.3.9), have been investigated. 1. Histone 2A and polycations activate the two enzymic activities. At a constant cation concentration, this activation increases with the number of cationic groups per molecule. 2. Activation by histone 2A is related to its fixation on microsomal membranes. This fixation varies with quantities of histones and pH. 3. The nature of the interactions between histones and microsomal membranes is shown to be electrostatic, probably between the cationic groups of histones and the anionic group of membranous lipids. 4. Kinetic analysis reveal that histone 2A increases the maximal reaction velocity but does not affect the apparent Michaelis constant values for the substrates. 5. The role played by the cationic groups of histone 2A on the microsomal glucose 6-phosphatase, is discussed.
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PMID:[Effects of basic proteins of low molecular weight on the phosphohydrolase and phosphotransferase activities of microsomal glucose-6-phosphatase in adult monkey hepatocytes (author's transl)]. 625 Jun 25

Histone 2A increases glucose-6-phosphatase activity in liver microsomes. The effect has been attributed either to the conformational change of the enzyme, or to the permeabilization of microsomal membrane that allows the free access of substrate to the intraluminal glucose-6-phosphatase catalytic site. The aim of the present study was the critical reinvestigation of the mechanism of action of histone 2A. It has been found that the dose-effect curve of histone 2A is different from that of detergents and resembles that of the pore-forming alamethicin. Inhibitory effects of EGTA on glucose-6-phosphatase activity previously reported in histone 2A-treated microsomes have been also found in alamethicin-permeabilized vesicles. The effect of EGTA cannot therefore simply be an antagonization of the effect of histone 2A. Histone 2A stimulates the activity of another latent microsomal enzyme, UDP-glucuronosyltransferase, which has an intraluminal catalytic site. Finally, histone 2A renders microsomal vesicles permeable to non-permeant compounds. Taken together, the results demonstrate that histone 2A stimulates glucose-6-phosphatase activity by permeabilizing the microsomal membrane.
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PMID:Histone 2A stimulates glucose-6-phosphatase activity by permeabilization of liver microsomes. 1209 38