Taurocholate

Taurocholate is the taurine conjugate of cholic acid, formed when cholic acid is amidated with taurine to yield taurocholic acid, a bile salt. In many mammals, it is present in bile as the sodium salt, sodium taurocholate. The molecule is amphipathic, with a hydrophobic steroid nucleus and a hydrophilic taurine moiety, giving it detergent properties that aid fat emulsification.

Biosynthesis occurs in the liver by conjugation of bile acid CoA derivatives with taurine, catalyzed by bile acid-CoA:amino acid N-acyltransferase (BAAT). This conjugation increases solubility and reduces passive diffusion from the intestinal lumen, enabling efficient secretion into bile. Taurocholate is commonly produced alongside other conjugates such as glycocholate, which uses glycine instead of taurine.

Physiological role is centered on digestion: taurocholate is secreted into bile and released into the small intestine during digestion, where it acts as an endogenous detergent to form mixed micelles with phospholipids and cholesterol. This micellar system facilitates the activity of pancreatic lipase and the absorption of fatty acids and fat-soluble vitamins. Taurocholate participates in enterohepatic circulation, being reabsorbed in the ileum via the apical sodium-dependent bile acid transporter and returned to the liver through the portal vein.

Clinical notes: variations in bile acid composition, including taurocholate levels, occur in liver or biliary diseases. Measurement of bile acids in serum or bile can aid in diagnosing cholestasis or hepatobiliary disorders, and excessive biliary bile acids may contribute to pruritus or hepatotoxicity in cholestasis.