Facilitative hexose transporter that mediates the transport of glucose, fructose and galactose (PubMed:3048704). Likely mediates the bidirectional transfer of glucose across the plasma membrane of hepatocytes and is responsible for uptake of glucose by the beta cells; may comprise part of the glucose-sensing mechanism of the beta cell (PubMed:3048704). May also participate with the Na(+)/glucose cotransporter in the transcellular transport of glucose in the small intestine and kidney (By similarity). Also able to mediate the transport of dehydroascorbate (By similarity). D-glucose(out) = D-glucose(in) D-fructose(out) = D-fructose(in) L-dehydroascorbate(out) = L-dehydroascorbate(in) D-galactose(in) = D-galactose(out) D-glucose and maltose competitively inhibit fructose transport. D-glucose, D-fructose and maltose inhibit deoxyglucose transport. Present in liver, intestine, kidney and beta-pancreatic islet cells. N-glycosylated; required for stability and retention at the cell surface of pancreatic beta cells. Belongs to the major facilitator superfamily. Sugar transporter (TC 2.A.1.1) family. Glucose transporter subfamily.