تسجيل الدخول

تسجيل

Biosynthesis of Bile Acids

المؤلف:  Norman, A. W., & Henry, H. L.

المصدر:  Hormones

الجزء والصفحة:  3rd edition , p51

2026-06-21

100

The conversion of cholesterol into bile acids takes place largely in the liver. In most mammals cholic acid and chenodeoxycholic acid are the principal bile acids. Before excretion into the bile, the carbon-24 carboxyl of both steroids is conjugated with the amino group of the amino acids taurine or glycine so as to increase the water solubility of the bile acids. The primary function of bile acids is to emulsify or solubilize ingested dietary fats, so as to facilitate their absorption and catabolism.

The steps involved in the conversion of cholesterol into a bile acid include the following: (i) cleavage of the side chain between carbon-24 and carbon-25; (ii) microsome mediated hydroxylations at carbon-7 and carbon-12; (iii) epimerization of the 3−β-hydroxyl to a 3α-α orientation; and (iv) reduction of the Δ5-double bond so that the A:B ring junction is cis.

In addition to the detergent property of bile acids, some of the bile acids function as a steroid hormone that is a ligand for the nuclear receptor, farnesoid X receptor (FXR). The bile acid liganded FXR receptor regulates gene transcription in the liver with the consequence that hepatic bile acid synthesis is inhibited. Also the bile acid liganded FXR may regulate glucose and triglyceride metabolism.