US EPA

7437097 

Journal Article 

Hormonal Regulation of Liver Cytochrome P450 Enzymes 

Waxman, DJ; Chang, TKH; , 

1995 

Springer US 

Boston, MA 

Cytochrome P450 

391-417 

10.1007/978-1-4757-2391-5_11 

http://link.springer.com/10.1007/978-1-4757-2391-5_11
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Endogenous steroids and other naturally occurring lipophilic substances serve as important substrates for cytochrome P450 (CYP) enzymes found in liver and other tissues,1,2 including the primary steroidogenic tissues (Kagawa and Waterman, this volume). Steroid hormones are metabolized by liver P450 enzymes with a higher degree of regio-and stereoselectivity than many foreign compound substrates,3 suggesting that these endogenous lipophiles serve as physiological P450 substrates. Eight of the twelve mammalian P450 gene families described as of 19934 encode enzymes that catalyze steroid hydroxylations. Two of these gene families (CYP2 and CYP3) encode liver P450 enzymes required for the hydroxylation of steroid hormones and bile acids, and two encode P450s that participate in the conversion of cholesterol to bile acids in the liver, where they contribute in a major way to cholesterol homeostasis (CYP7, CYP27).5