Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9012987 | Life Sciences | 2005 | 12 Pages |
Abstract
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 α-methyl-D-glucopyranoside (AMG) transport activity with an apparent Km 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).
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Authors
Shigeki Tazawa, Tokuhisa Yamato, Hideki Fujikura, Masahiro Hiratochi, Fumiaki Itoh, Masaki Tomae, Yukiko Takemura, Hidetoshi Maruyama, Tomoyasu Sugiyama, Ai Wakamatsu, Takao Isogai, Masayuki Isaji,