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. 2016 Mar 3;7(1):22–39. doi: 10.1080/19490976.2015.1127483

Figure 2.

Figure 2.

Synthesis of primary bile acids in the liver and biotransformations of bile acids carried out by gut bacteria. In humans, the liver synthesizes cholic acid and chenodeoxycholic acid from cholesterol. The major quantitative and irreversible reactions carried out by gut bacteria include the hydrolysis of conjugated bile acids by BSH and 7α-dehydroxylation of cholic acid and chenodeoxycholic acid. More than 20 bile acid metabolites can be produced from primary bile acids by the gut microbiota. Abb. BSH, bile salt hydrolase; 3α-HSDH, 3α-hydroxysteroid dehydrogenase; 3β-HSDH, 3β-hydroxysteroid dehydrogenase; 7α-HSDH, 7α-hydroxysteroid dehydrogenase; 7β-HSDH, 7β-hydroxysteroid dehydrogenase; 12α-HSDH, 12α-hydroxysteroid dehydrogenase; 12β-HSDH, 12β-hydroxysteroid dehydrogenase.