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Emile Van Schaftingen - One of the best experts on this subject based on the ideXlab platform.
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Evidence for Glucose-6-Phosphate transport in rat liver microsomes.
FEBS letters, 2002Co-Authors: Isabelle Gerin, Emile Van SchaftingenAbstract:The existence of Glucose-6-Phosphate transport across the liver microsomal membrane is still controversial. In this paper, we show that S3483, a chlorogenic acid derivative known to inhibit Glucose-6-phosphatase in intact microsomes, caused the intravesicular accumulation of Glucose-6-Phosphate when the latter was produced by Glucose-6-phosphatase from Glucose and carbamoyl-Phosphate. S3483 also inhibited the conversion of Glucose-6-Phosphate to 6-phosphogluconate occurring inside microsomes in the presence of electron acceptors (NADP or metyrapone). These data indicate that liver microsomal membranes contain a reversible Glucose-6-Phosphate transporter, which furnishes substrate not only to Glucose-6-phosphatase, but also to hexose-6-Phosphate dehydrogenase.
A Benedetti - One of the best experts on this subject based on the ideXlab platform.
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Permeability of rat liver microsomal membrane to Glucose 6-Phosphate.
The Biochemical journal, 1992Co-Authors: R Fulceri, G Bellomo, A Gamberucci, H M Scott, A Burchell, A BenedettiAbstract:Light-scattering measurements of osmotically induced changes in the size of rat liver microsomal vesicles pre-equilibrated in a low-osmolality buffer revealed the following. (1) The increase in extravesicular osmolality by addition of Glucose 6-Phosphate or mannose 6-Phosphate (25 mM each) caused a rapid shrinking of microsomal vesicles. After shrinkage, a rapid swelling phase (t1/2 approx. 22 s) was present with Glucose 6-Phosphate but absent with mannose 6-Phosphate, indicating that the former had entered microsomal vesicles, but the latter had not. (2) Almost identical results were obtained in the absence of any Glucose 6-Phosphate hydrolysis, i.e. with microsomes pre-treated with 100 microM-vanadate. (3) The anion-channel blocker 4,4'-di-isothiocyanostilbene-2,2'-disulphonic acid (DIDS) suppressed the Glucose 6-Phosphate-induced swelling phase. (4) The swelling phase was more prolonged as the Glucose 6-Phosphate concentration increased (t1/2 = 16 +/- 3, 22 +/- 3 and 35 +/- 4 s with 25 mM, 37.5 mM- and 50 mM-Glucose 6-Phosphate respectively). The behaviour of Glucose-6-phosphatase activity of intact and disrupted microsomes measured in the presence of high concentrations (less than 30 mM) of substrate also indicated the saturation of the Glucose 6-Phosphate permeation system by extravesicular concentrations of Glucose 6-Phosphate higher than 20-30 mM. Additional experiments showed that vanadate-treated microsomes pre-equilibrated with 0.1 mM- and 1.0 mM-Glucose 6-Phosphate (and [1-14C]Glucose 6-Phosphate as a tracer) rapidly (t1/2 less than 20 s) released [1-14C]Glucose 6-Phosphate when diluted in a Glucose 6-Phosphate-free medium. The efflux of [1-14C]Glucose 6-Phosphate was largely prevented by DIDS, allowing an evaluation of the intravesicular space of Glucose 6-Phosphate of approx. 1.0 microliter/mg of microsomal protein.
Angelo Benedetti - One of the best experts on this subject based on the ideXlab platform.
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The Glucose-6-Phosphate transport is not mediated by a Glucose-6-Phosphate/Phosphate exchange in liver microsomes
FEBS letters, 2012Co-Authors: Paola Marcolongo, Rosella Fulceri, Roberta Giunti, Éva Margittai, Gábor Bánhegyi, Angelo BenedettiAbstract:A Phosphate-linked antiporter activity of the Glucose-6-Phosphate transporter (G6PT) has been recently described in liposomes including the reconstituded transporter protein. We directly investigated the mechanism of Glucose-6-Phosphate (G6P) transport in rat liver microsomal vesicles. Pre-loading with inorganic Phosphate (Pi) did not stimulate G6P or Pi microsomal inward transport. Pi efflux from pre-loaded microsomes could not be enhanced by G6P or Pi addition. Rapid G6P or Pi influx was registered by light-scattering in microsomes not containing G6P or Pi. The G6PT inhibitor, S3483, blocked G6P transport irrespectively of experimental conditions. We conclude that hepatic G6PT functions as an uniporter.
Isabelle Gerin - One of the best experts on this subject based on the ideXlab platform.
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Evidence for Glucose-6-Phosphate transport in rat liver microsomes.
FEBS letters, 2002Co-Authors: Isabelle Gerin, Emile Van SchaftingenAbstract:The existence of Glucose-6-Phosphate transport across the liver microsomal membrane is still controversial. In this paper, we show that S3483, a chlorogenic acid derivative known to inhibit Glucose-6-phosphatase in intact microsomes, caused the intravesicular accumulation of Glucose-6-Phosphate when the latter was produced by Glucose-6-phosphatase from Glucose and carbamoyl-Phosphate. S3483 also inhibited the conversion of Glucose-6-Phosphate to 6-phosphogluconate occurring inside microsomes in the presence of electron acceptors (NADP or metyrapone). These data indicate that liver microsomal membranes contain a reversible Glucose-6-Phosphate transporter, which furnishes substrate not only to Glucose-6-phosphatase, but also to hexose-6-Phosphate dehydrogenase.
R Fulceri - One of the best experts on this subject based on the ideXlab platform.
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Permeability of rat liver microsomal membrane to Glucose 6-Phosphate.
The Biochemical journal, 1992Co-Authors: R Fulceri, G Bellomo, A Gamberucci, H M Scott, A Burchell, A BenedettiAbstract:Light-scattering measurements of osmotically induced changes in the size of rat liver microsomal vesicles pre-equilibrated in a low-osmolality buffer revealed the following. (1) The increase in extravesicular osmolality by addition of Glucose 6-Phosphate or mannose 6-Phosphate (25 mM each) caused a rapid shrinking of microsomal vesicles. After shrinkage, a rapid swelling phase (t1/2 approx. 22 s) was present with Glucose 6-Phosphate but absent with mannose 6-Phosphate, indicating that the former had entered microsomal vesicles, but the latter had not. (2) Almost identical results were obtained in the absence of any Glucose 6-Phosphate hydrolysis, i.e. with microsomes pre-treated with 100 microM-vanadate. (3) The anion-channel blocker 4,4'-di-isothiocyanostilbene-2,2'-disulphonic acid (DIDS) suppressed the Glucose 6-Phosphate-induced swelling phase. (4) The swelling phase was more prolonged as the Glucose 6-Phosphate concentration increased (t1/2 = 16 +/- 3, 22 +/- 3 and 35 +/- 4 s with 25 mM, 37.5 mM- and 50 mM-Glucose 6-Phosphate respectively). The behaviour of Glucose-6-phosphatase activity of intact and disrupted microsomes measured in the presence of high concentrations (less than 30 mM) of substrate also indicated the saturation of the Glucose 6-Phosphate permeation system by extravesicular concentrations of Glucose 6-Phosphate higher than 20-30 mM. Additional experiments showed that vanadate-treated microsomes pre-equilibrated with 0.1 mM- and 1.0 mM-Glucose 6-Phosphate (and [1-14C]Glucose 6-Phosphate as a tracer) rapidly (t1/2 less than 20 s) released [1-14C]Glucose 6-Phosphate when diluted in a Glucose 6-Phosphate-free medium. The efflux of [1-14C]Glucose 6-Phosphate was largely prevented by DIDS, allowing an evaluation of the intravesicular space of Glucose 6-Phosphate of approx. 1.0 microliter/mg of microsomal protein.