title: Evaluation of enzyme activities by gas chromatography-mass spectrometry: HMGCoA reductase and cholesterol 7 alpha-hydroxylase.
abstract: Methods are described for the evaluation of HMGCoA reductase and cholesterol 7 alpha-hydroxylase activities. The methods are based on the measurement by selected-ion monitoring of mevalonate, formed from HMGCoA and of 7 alpha-hydroxycholesterol formed from cholesterol, respectively. The methods are as sensitive as those based on the use of radioisotopes but less time-consuming because quantitation is carried out on total lipid extracts. In the case of cholesterol 7 alpha-hydroxylase, the procedure does not require the use of exogenous cholesterol as the substrate, so problems related to its equilibration with endogenous microsomal cholesterol are avoided.
mesh_terms: D000818:Animals; D002790:Cholesterol 7-alpha-Hydroxylase / Q000032:analysis*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006903:Hydroxymethylglutaryl CoA Reductases / Q000032:analysis*; D066298:In Vitro Techniques; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology; D051381:Rats; D013250:Steroid Hydroxylases / Q000032:analysis*
chemical_list: D006903:Hydroxymethylglutaryl CoA Reductases; D013250:Steroid Hydroxylases; D002790:Cholesterol 7-alpha-Hydroxylase