Taurine Conjugation of Bile Acids Protects Human Cells in Culture
Primary bile acids such as cholate and chenodeoxycholate are the end products of hepatic cholesterol catabolism. In most healthy animals not more than trace amounts of free bile acids occur in bile and plasma, even though unconjugated forms are present in gallstones and feces. Most placental animals including man, can conjugate bile acids with either glycine or taurine (5). Since the affinity of taurine is higher for the conjugating enzyme, bile acid-CoA: amino acid H-acyltransferase (4), taurine is generally considered the preferred substrate for bile acid conjugation (4,6). After conjugation bile acids are excreted into the bile and subsequently released into the intestinal tract where they are subject to deconjugation and 7 α-dehydroxylation. These reactions are catalyzed by intestinal strains of Clostridium, Enterococcus, Bacteroides, and Lactobacillus (5). Removal of the 7 α-hydroxyl group results in the formation of the secondary bile acids: deoxycholate from cholate and lithocholate from chenodeoxycholate. Except for lithocholate which is normally excreted in the feces, all other free and conjugated bile acids are absorbed in the ileum and recycled to the liver.
KeywordsBile Acid Cholanic Acid Cell Line NB76 Conjugate Bile Acid Secondary Bile Acid
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