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. Author manuscript; available in PMC: 2016 Jan 1.
Published in final edited form as: Biochim Biophys Acta. 2014 May 4;1851(1):19–29. doi: 10.1016/j.bbalip.2014.04.008

Fig 1. Bile acid synthesis.

Fig 1

In the classic bile acid synthesis pathway, cholesterol is converted to cholic acid (CA, 3α, 7α, 12α) and chenodeoxycholic acid (CDCA, 3α, 7α) CYP7A1 is the rate-limiting enzyme and CYP8B1 catalyzes the synthesis of CA. In mouse liver, CDCA is converted to α-muricholic acid (α-MCA, 3α, 6β, 7α) and β-MCA (3α, 6β, 7β) Most bile acids in mice are taurine (T)-conjugated and secreted into bile. In the intestine, gut bacteria de-conjugate bile acids and then remove the 7α-hydroxyl group from CA and CDCA to form secondary bile acids deoxycholic acid (DCA, 3α, 12α) and lithocholic acid (LCA, 3α), respectively. T-α-MCA and T-β-MCA are converted to T-hyodeoxycholic acid (THDCA, 3α, 6α), T-ursodeoxycholic acid (TUDCA, 3α, 7β), T-hyocholic acid (THCA, 3α, 6α, 7α) and T-murideoxycholic acid (TMDCA, 3α, 6β). These secondary bile acids are reabsorbed and circulated to liver to contribute to the bile acid pool. Secondary bile acids ω-MCA (3α, 6α, 7β) and LCA are excreted into feces.