Synthesis of 27-hydroxycholesterol in rat liver mitochondria: HPLC assay and marked activation by exogenous cholesterol
| Autor: | Brian Jude Latario, Barbara Petrack |
|---|---|
| Rok vydání: | 1993 |
| Předmět: |
biology
Cholesterol oxidase Reverse cholesterol transport Sterol O-acyltransferase QD415-436 Cell Biology Cholesterol 7 alpha-hydroxylase Biochemistry Sterol Enzyme assay chemistry.chemical_compound Endocrinology chemistry 27-Hydroxycholesterol polycyclic compounds biology.protein lipids (amino acids peptides and proteins) Cholesterol 24-hydroxylase |
| Zdroj: | Journal of Lipid Research, Vol 34, Iss 4, Pp 643-649 (1993) |
| ISSN: | 0022-2275 |
| DOI: | 10.1016/s0022-2275(20)39988-0 |
| Popis: | Sterol 27-hydroxylase, the mitochondrial enzyme that catalyzes the first step in oxidation of the sterol side chain in hepatic bile acid synthesis, also catalyzes the synthesis of 27-hydroxycholesterol from cholesterol. We have developed a high performance liquid chromatography (HPLC) assay for this enzyme, using either endogenous or exogenous cholesterol as substrate and cholesterol oxidase to convert 27-hydroxycholesterol to 4-cholesten-27-hydroxy-3-one. The alpha,beta-unsaturated ketone product was separated by normal phase HPLC and quantitated via absorption at 240 nm. Addition of cholesterol dissolved in 2-hydroxypropyl-beta-cyclodextrin to the assay mixture raised the enzyme activity of rat liver mitochondria more than 10-fold. 2-Hydroxypropyl-beta-cyclodextrin itself was partially effective, apparently by making more endogenous cholesterol accessible to the enzyme. Availability of cholesterol to the enzyme limits synthesis of 27-hydroxycholesterol in rat liver. Using our assay to simultaneously determine the activities of cholesterol 7 alpha-hydroxylase and cholesterol 27-hydroxylase in rat liver homogenates, we demonstrated that the two enzymes are separately regulated. |
| Databáze: | OpenAIRE |
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