Journal
LIFE SCIENCES
Volume 76, Issue 9, Pages 1039-1050Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.lfs.2004.10.016
Keywords
SLC5A; SGLT; D-glucose; D-mannose; 1,5-anhydro-D-glucitol; D-fructose
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We isolated a cDNA clone of SLC5A9/SGLT4 from human small intestinal full-length cDNA libraries, and functionally characterized it in vitro. The messenger RNA encoding SGLT4 was mainly expressed in the small intestine and kidney, among the human tissues tested. COS-7 cells transiently expressing SGLT4 exhibited Na+-dependent alpha-methyl-D-glucopyranoside (AMG) transport activity with an apparent K-m of 2.6 mM, suggesting that SGLT4 is a low affinity-type transporter. The rank order of naturally occurring sugar analogs for the inhibition of AMG transport was: D-mannose (Man) >> D-glucose (Glc) > D-fructose (Fru) = 1,5-anhydro-D-glucitol (1,5AG) > D-galactose (Gal). Recognition of Man as a substrate was confirmed by direct uptake of Man into the cell. COS-7 cells expressing a putative murine SGLT4 ortholog showed similar Na+-dependent AMG transport activity and a similar deduced substrate specificity. These results suggest that SGLT4 would have unique physiological functions (i.e., absorption and/or reabsorption of Man, 1,5AG, and Fru, in addition to Glc). (C) 2004 Elsevier Inc. All rights reserved.
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