Reaction participants Show >> << Hide
- Name help_outline tauroursodeoxycholate Identifier CHEBI:132028 Charge -1 Formula C26H44NO6S InChIKeyhelp_outline BHTRKEVKTKCXOH-LBSADWJPSA-M SMILEShelp_outline C1[C@@]2([C@]3(CC[C@]4([C@]([C@@]3([C@H](C[C@@]2(C[C@@H](C1)O)[H])O)[H])(CC[C@]4([H])[C@@H](CCC(NCCS([O-])(=O)=O)=O)C)[H])C)[H])C 2D coordinates Mol file for the small molecule Search links Involved in 5 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline Na+ Identifier CHEBI:29101 (CAS: 17341-25-2) help_outline Charge 1 Formula Na InChIKeyhelp_outline FKNQFGJONOIPTF-UHFFFAOYSA-N SMILEShelp_outline [Na+] 2D coordinates Mol file for the small molecule Search links Involved in 259 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
Cross-references
| RHEA:71927 | RHEA:71928 | RHEA:71929 | RHEA:71930 | |
|---|---|---|---|---|
| Reaction direction help_outline | undefined | left-to-right | right-to-left | bidirectional |
| UniProtKB help_outline |
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Publications
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Substrate specificity of the ileal and the hepatic Na(+)/bile acid cotransporters of the rabbit. I. Transport studies with membrane vesicles and cell lines expressing the cloned transporters.
Kramer W., Stengelin S., Baringhaus K.H., Enhsen A., Heuer H., Becker W., Corsiero D., Girbig F., Noll R., Weyland C.
The substrate specificity of the ileal and the hepatic Na(+)/bile acid cotransporters was determined using brush border membrane vesicles and CHO cell lines permanently expressing the Na(+)/bile acid cotransporters from rabbit ileum or rabbit liver. The hepatic transporter showed a remarkably broa ... >> More
The substrate specificity of the ileal and the hepatic Na(+)/bile acid cotransporters was determined using brush border membrane vesicles and CHO cell lines permanently expressing the Na(+)/bile acid cotransporters from rabbit ileum or rabbit liver. The hepatic transporter showed a remarkably broad specificity for interaction with cholephilic compounds in contrast to the ileal system. The anion transport inhibitor diisothiocyanostilbene disulfonate (DIDS) is a strong inhibitor of the hepatic Na(+)/bile acid cotransporter, but does not show any affinity to its ileal counterpart. Inhibition studies and uptake measurements with about 40 different bile acid analogues differing in the number, position, and stereochemistry of the hydroxyl groups at the steroid nucleus resulted in clear structure;-activity relationships for the ileal and hepatic bile acid transporters. The affinity to the ileal and hepatic Na(+)/bile acid cotransport systems and the uptake rates by cell lines expressing those transporters as well as rabbit ileal brush border membrane vesicles is primarily determined by the substituents on the steroid nucleus. Two hydroxy groups at position 3, 7, or 12 are optimal whereas the presence of three hydroxy groups decreased affinity. Vicinal hydroxy groups at positions 6 and 7 or a shift of the 7-hydroxy group to the 6-position significantly decreased the affinity to the ileal transporter in contrast to the hepatic system. 6-Hydroxylated bile acid derivatives are preferred substrates of the hepatic Na(+)/bile acid cotransporter. Surprisingly, the 3alpha-hydroxy group being present in all natural bile acids is not essential for high affinity interaction with the ileal and the hepatic bile acid transporter. The 3alpha-hydroxy group seems to be necessary for optimal transport of a bile acid across the hepatocyte canalicular membrane. A modification of bile acids at the 3-position therefore conserves the bile acid character thus determining the 3-position of bile acids as the ideal position for drug targeting strategies using bile acid transport pathways. << Less
J. Lipid Res. 40:1604-1617(1999) [PubMed] [EuropePMC]
This publication is cited by 8 other entries.
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Substrate specificity of the rat liver Na(+)-bile salt cotransporter in Xenopus laevis oocytes and in CHO cells.
Schroeder A., Eckhardt U., Stieger B., Tynes R., Schteingart C.D., Hofmann A.F., Meier P.J., Hagenbuch B.
It has been proposed that the hepatocellular Na(+)-dependent bile salt uptake system exhibits a broad substrate specificity in intact hepatocytes. In contrast, recent expression studies in mammalian cell lines have suggested that the cloned rat liver Na(+)-taurocholate cotransporting polypeptide ( ... >> More
It has been proposed that the hepatocellular Na(+)-dependent bile salt uptake system exhibits a broad substrate specificity in intact hepatocytes. In contrast, recent expression studies in mammalian cell lines have suggested that the cloned rat liver Na(+)-taurocholate cotransporting polypeptide (Ntcp) may transport only taurocholate. To characterize its substrate specificity Ntcp was stably transfected into Chinese hamster ovary (CHO) cells. These cells exhibited saturable Na(+)-dependent uptake of [3H]taurocholate [Michaelis constant (K(m)) of approximately 34 microM] that was strongly inhibited by all major bile salts, estrone 3-sulfate, bumetanide, and cyclosporin A. Ntcp cRNA-injected Xenopus laevis oocytes and the transfected CHO cells exhibited saturable Na(+)-dependent uptake of [3H]taurochenodeoxycholate (Km of approximately 5 microM), [3H]tauroursodeoxycholate (Km of approximately 14 microM), and [14C]glycocholate (Km of approximately 27 microM). After induction of gene expression by sodium butyrate, Na(+)-dependent transport of [3H]estrone 3-sulfate (Km of approximately 27 microM) could also be detected in the transfected CHO cells. However, there was no detectable Na(+)-dependent uptake of [3H]bumetanide or [3H]cyclosporin A. These results show that the cloned Ntcp can mediate Na(+)-dependent uptake of all physiological bile salts as well as of the steroid conjugate estrone 3-sulfate. Hence, Ntcp is a multispecific transporter with preference for bile salts and other anionic steroidal compounds. << Less
Am. J. Physiol. 274:G370-G375(1998) [PubMed] [EuropePMC]
This publication is cited by 4 other entries.