Reactome | Synthesis of bile acids and bile salts via 27-hydroxycholesterol

Synthesis of bile acids and bile salts via 27-hydroxycholesterol

Stable Identifier

R-HSA-193807

Type

Pathway

Species

Homo sapiens

ReviewStatus

5/5

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Synthesis of bile acids and bile salts via 27-hydroxycholesterol

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In the body, 27-hydroxycholesterol is synthesized in multiple tissues, exported to the liver, and converted there to bile acids and bile salts. This pathway is only a minor source of bile acids and bile salts, but may play a significant role particularly in the mobilization of cholesterol from lung phagocytes (Bjorkhem et al. 1994; Babiker et al. 1999; Javitt 2002).

In the liver, conversion of 27-hydroxycholesterol to bile acids and bile salts is initiated with hydroxylation and oxidoreductase reactions to form 4-cholesten-7alpha,27-diol-3-one. The pathway then branches: hydroxylation of 4-cholesten-7alpha,27-diol-3-one to 4-cholesten-7alpha,12alpha,27-triol-3-one leads ultimately to the formation of cholate, while its reduction to 5beta-cholestan-7alpha,27-diol-3-one leads to chenodeoxycholate formation. In both branches, reactions in the cytosol, the mitochondrial matrix, and the peroxisomal matrix result in modifications to the ring structure, shortening and oxidation of the side chain, conversion to a Coenzyme A derivative, and conjugation with the amino acids glycine or taurine (Russell 2003). These reactions are outlined in the figure below. The final nine reactions are identical to ones of bile salt synthesis initiated by 7alpha-hydroxylation and are shown as arrows with no substrates.

Literature References

PubMed ID	Title	Journal	Year
8078928	Atherosclerosis and sterol 27-hydroxylase: evidence for a role of this enzyme in elimination of cholesterol from human macrophages Duan, C, Andersson, O, Lund, E, Bjorkhem, I, Diczfalusy, U, Xiu, RJ, Sevastik, B	Proc Natl Acad Sci U S A	1994
10428977	Elimination of cholesterol as cholestenoic acid in human lung by sterol 27-hydroxylase: evidence that most of this steroid in the circulation is of pulmonary origin Lutjohann, D, Andersson, O, van der Linden, J, Bjorkhem, I, Wiklund, B, Diczfalusy, U, Lindblom, D, Babiker, A	J Lipid Res	1999
12543708	The enzymes, regulation, and genetics of bile acid synthesis Russell, DW	Annu Rev Biochem	2003
11969205	Cholesterol, hydroxycholesterols, and bile acids Javitt, NB	Biochem Biophys Res Commun	2002