-
Categories
-
Pharmaceutical Intermediates
-
Active Pharmaceutical Ingredients
-
Food Additives
- Industrial Coatings
- Agrochemicals
- Dyes and Pigments
- Surfactant
- Flavors and Fragrances
- Chemical Reagents
- Catalyst and Auxiliary
- Natural Products
- Inorganic Chemistry
-
Organic Chemistry
-
Biochemical Engineering
- Analytical Chemistry
- Cosmetic Ingredient
-
Pharmaceutical Intermediates
Promotion
ECHEMI Mall
Wholesale
Weekly Price
Exhibition
News
-
Trade Service
CYP7A1, which is the only CYP7A subfamily P450 tdentified to date (
1
), catalyzes cholesterol 7α-hydroxylation, the first, and rate-limiting, step in the converston of cholesterol to bile acids. CYP7Al has been Isolated from human liver and purified to apparent homogeneity (
2
). Rodent-model studies have established that CYP7A1 is highly regulated by physiological factors that influence hepatic-bile-acid biosynthesis, including cholesterol feedmg, dmrnal factors, and bile acids, whtch feedback-inhibit the overall btosynthetlc pathway in large part at the level of CYP7A1 gene expression (
3
). Relatrvely little is known about the regulation of human CYP7A1, although liver biopsy analyses have shown that hepatic CYP7A1 protem content is elevated in patients treated with the bile-acid sequesterant cholestyramme (
4
). Purified CYP7A1 is catalytically active in cholesterol 7α-hydroxylation (
2
) and immunoinhibition experiments with antihuman CYP7A1 antibodies have shown that CYP7A1 accounts for most of the cholesterol 7a-hydroxylase acttvtty in human liver microsomes (
4
). Thus, mlcrosomal cholesterol 7α-hydroxylase activity can be used as a marker for human liver CYP7A1. Several analytical methods have been developed to quantify hepatrc mrcrosomal cholesterol 7α-hydroxylation, including reversed-phase high-performance hquid chromatography (RPHPLC) (
5
), isotope dilution-mass spectrometry (
6
) and thin-layer chromatography (TLC) (
7
). This chapter describes a normal-phase, isocratic HPLC assay for the determination of cholesterol 7α-hydroxylase acttvity based on the conversion by cholesterol oxidase of the primary P450 metabohte 7α-hydroxycholesterol to 7α-hydroxy-4-cholesten-3-one, which can be detected at 254 nm.