The glucose-6-phosphate transport is not mediated by a glucose-6-phosphate/phosphate exchange in liver microsomes |
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| Authors: | Paola Marcolongo Rosella Fulceri Roberta Giunti Eva Margittai Gabor Banhegyi Angelo Benedetti |
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| Affiliation: | a Department of Pathophysiology, Experimental Medicine and Public Health, Via A. Moro no. 1, University of Siena, 53100-Siena, Italy
b Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Budapest, Hungary |
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| Abstract: | 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. |
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| Keywords: | G6PT, glucose-6-phosphate transporter G6P, glucose-6-phosphate ER, endoplasmic reticulum Pi, inorganic phosphate G6Pase, glucose-6-phosphatase H6PD, hexose-6-phosphate dehydrogenase DIDS, 4,4&prime -diisothiocyanostilbene-2,2&prime -disulfonic acid Mops, 3-(N-morpholino)propanesulfonic acid |
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