Publications

• The lithocholic acid 6 beta-hydroxylase cytochrome P-450, CYP 3A10, is an active catalyst of steroid-hormone 6 beta-hydroxylation.

  Chang T.K.H., Teixeira J., Gil G., Waxman D.J.

  CYP 3A10 is a hamster liver cytochrome P-450 (P450) that encodes lithocholic acid 6 beta-hydroxylase, an enzyme that plays an important role in the detoxification of the cholestatic secondary bile acid lithocholate. Western-blot analysis revealed that the expression of CYP 3A10 protein is male-spe ... >> More

  CYP 3A10 is a hamster liver cytochrome P-450 (P450) that encodes lithocholic acid 6 beta-hydroxylase, an enzyme that plays an important role in the detoxification of the cholestatic secondary bile acid lithocholate. Western-blot analysis revealed that the expression of CYP 3A10 protein is male-specific in hamster liver microsomes, a finding that is consistent with earlier analysis of CYP 3A10 mRNA. Since it has not been established whether the specificities of bile acid hydroxylase P450s, such as CYP 3A10, are restricted to their anionic bile acid substrates, we investigated the role of CYP 3A10 in the metabolism of a series of neutral steroid hormones using cDNA directed-expression in COS cells. The steroid hormones examined, testosterone, androstenedione and progesterone, were each metabolized by the expressed CYP 3A10, with 6 beta-hydroxylation corresponding to a major activity in all three instances. CYP 3A10-dependent steroid hydroxylation was increased substantially when the microsomes were prepared from COS cells co-transfected with NADPH:P450 reductase cDNA. In this case, the expressed P450 actively catalysed the 6 beta-hydroxylation of testosterone (288 +/-23 pmol of product formed/min per mg of COS-cell microsomal protein), androstenedione (107 +/- 19 pmol/min per mg) and progesterone (150 +/-7 pmol/min per mg). Other major CYP 3A10-mediated steroid hydroxylase activities included androstenedione 16 alpha-hydroxylation, progesterone 16 alpha- and 21-hydroxylation, and the formation of several unidentified products. CYP 3A10 exhibited similar Vmax. values for the 6 beta-hydroxylation of androstenedione and lithocholic acid (132 and 164 pmol/min per mg respectively), but metabolized the bile acid with a 3-fold lower Km (25 microM, as against 75 microM for androstenedione). Together, these studies establish that the substrate specificity of the bile acid hydroxylase CYP 3A10 is not restricted to bile acids, and further suggest that CYP 3A10 can play a physiologically important role in the metabolism of two classes of endogenous P450 substrates:steroid hormones and bile acids. << Less

  Biochem. J. 291:429-433(1993) [PubMed] [EuropePMC]

• The enzymes, regulation, and genetics of bile acid synthesis.

  Russell D.W.

  The synthesis and excretion of bile acids comprise the major pathway of cholesterol catabolism in mammals. Synthesis provides a direct means of converting cholesterol, which is both hydrophobic and insoluble, into a water-soluble and readily excreted molecule, the bile acid. The biosynthetic steps ... >> More

  The synthesis and excretion of bile acids comprise the major pathway of cholesterol catabolism in mammals. Synthesis provides a direct means of converting cholesterol, which is both hydrophobic and insoluble, into a water-soluble and readily excreted molecule, the bile acid. The biosynthetic steps that accomplish this transformation also confer detergent properties to the bile acid, which are exploited by the body to facilitate the secretion of cholesterol from the liver. This role in the elimination of cholesterol is counterbalanced by the ability of bile acids to solubilize dietary cholesterol and essential nutrients and to promote their delivery to the liver. The synthesis of a full complement of bile acids requires 17 enzymes. The expression of selected enzymes in the pathway is tightly regulated by nuclear hormone receptors and other transcription factors, which ensure a constant supply of bile acids in an ever changing metabolic environment. Inherited mutations that impair bile acid synthesis cause a spectrum of human disease; this ranges from liver failure in early childhood to progressive neuropathy in adults. << Less

  Annu. Rev. Biochem. 72:137-174(2003) [PubMed] [EuropePMC]

  This publication is cited by 13 other entries.

• Cloning, expression and regulation of lithocholic acid 6beta-hydroxylase.

  Teixeira J., Gil G.

  We have isolated a hamster liver cDNA whose expression is induced upon feeding hamsters with a cholic acid-rich diet. It was identified as a cytochrome P450 family 3 protein, by sequence homology, and named CYP3A10. The activity of CYP3A10 was determined by transient expression of its cDNA in tran ... >> More

  We have isolated a hamster liver cDNA whose expression is induced upon feeding hamsters with a cholic acid-rich diet. It was identified as a cytochrome P450 family 3 protein, by sequence homology, and named CYP3A10. The activity of CYP3A10 was determined by transient expression of its cDNA in transfected COS cells and was found to hydroxylate lithocholic acid at position 6 beta. CYP3A10 RNA is 50-fold higher in males than in female hamsters. In males, it appears to be regulated by age with expression highest after puberty. Shortly after weaning (28 days), cholic acid feeding of male hamsters elevates the level of message over that of hamsters fed with normal laboratory chow. Females do not exhibit regulation by cholic acid. In hamster liver, murideoxycholic acid, the 6 beta-metabolite of lithocholic acid, is the major hydroxylated product of lithocholic acid. Lithocholic acid 6 beta-hydroxylase (6 beta-hydroxylase) activity is greatly diminished in hamster female liver microsomes as would be expected due to the lack of CYP3A10 mRNA in females. Additionally, male liver microsomal 6 beta-hydroxylase activity was increased by cholic acid feeding, consistent with the cholic acid-mediated induction of its RNA. These results indicate that, in male hamsters, 6 beta-hydroxylation is the major pathway for detoxification of lithocholate and that, likely, CYP3A10 is responsible for that activity. << Less

  J. Biol. Chem. 266:21030-21036(1991) [PubMed] [EuropePMC]