CLINICAL CASES
291
B IO C H E M IS T R Y PE A R L S
Bile salts are the major component of bile and are very efficient
“detergents” when conjugated to amino acids because of the pres-
ence of both polar and nonpolar regions, aiding in fat digestion.
The initial and rate-limiting step of bile acid synthesis is oxidation
of cholesterol to 7a-hydroxycholesterol by a mixed function oxi-
dase from the cytochrome P450 superfamily, cholesterol 7a-
hydroxylase (
CYP7A1
).
The synthesis of bile salts is under very tight regulatory control,
mainly by a feedback mechanism on cholesterol 7a-hydroxylase,
the rate-limiting enzyme in the synthetic pathway.
REFERENCES
Chiang JYL. Regulation of bile acid synthesis. Front Biosci 1998;3:D176-93.
Pullinger CR, Eng C, Salen G, et al. Human cholesterol 7a-hydroxylase (CYP7A1)
deficiency has a hypercholesterolemic phenotype. J Clin Invest 2002;
110(1):109-17.
Russell DW. The enzymes, regulation, and genetics of bile acid synthesis. Annu Rev
Biochem 2003;72:137-74.
Trauner M, Boyer JL. Bile salt transporters: molecular characterization, function,
and regulation. Physiol Rev 2003;83(2):633-71.
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