Functions as a fructose transporter that has only low activity with other monosaccharides (PubMed:12031501, PubMed:19091748). Can mediate the uptake of deoxyglucose, but with low efficiency (By similarity). Essential for fructose uptake in the small intestine (PubMed:19091748, PubMed:26071406). Plays a role in the regulation of salt uptake and blood pressure in response to dietary fructose (PubMed:19091748). Required for the development of high blood pressure in response to high dietary fructose intake (PubMed:19091748). D-fructose(out) = D-fructose(in) Fructose uptake is inhibited by cytochalasin B. Localized on the apical membrane of jejunum villi, but also on lateral plasma membranes of the villi (PubMed:18496516, PubMed:26071406). Transport to the cell membrane is dependent on RAB11A (PubMed:26071406). Detected at the apical membrane of villi in the jejunum (PubMed:18496516, PubMed:19091748, PubMed:26071406). Detected in jejunum mucosa (PubMed:26071406). Detected in epididymis and whole testis (at protein level) (PubMed:18417103). Detected in small intestine, kidney and testis (PubMed:12031501, PubMed:18417103, PubMed:19091748). Detected in cochlea, but not in inner or outer cochlear hair cells (PubMed:18417103). Up-regulated in jejunum by dietary fructose intake (at protein level) (PubMed:18496516). Up-regulated in jejunum by dietary fructose intake (PubMed:18496516, PubMed:26071406). Up-regulated by dietary fructose intake in small intestine and testis (PubMed:12031501). Mice fed a standard diet appear normal and healthy, and display no visible phenotype (PubMed:18417103, PubMed:19091748, PubMed:26071406). Mutant mice show reduced food intake when kept on a high-frucose diet and about 28% reduction of their body weight within seven days. They loose more weight than wild-type mice that receive similar amounts of high-fructose food (PubMed:19091748). Mutant mice show strongly decreased fructose absorption in the jejunum (PubMed:19091748, PubMed:26071406). Contrary to wild-type, mutant mice have a strongly distended colon and caecum when kept on a high-fructose diet. Their intestines look normal when they are fed a standard diet. Contrary to wild-type, mutant mice do not display increased fructose levels in blood serum when kept on a high-fructose diet. Contrary to wild-type, they do not show increased salt absorption in response to fructose, and do not develop high blood pressure in response to fructose feeding. On the contrary, the blood pressure of mutant mice is strongly decreased after five days on a high-fructose diet. Mutant mice develop hypovolemic shock and die after 7 to 10 days on high-fructose diet (PubMed:19091748). Mutant mice display no defects of cochlear morphology or any hearing defects (PubMed:18417103). Belongs to the major facilitator superfamily. Sugar transporter (TC 2.A.1.1) family. Glucose transporter subfamily.