Method of quantifying cholesterol in high density lipoprotein and reagent compositions
A method for specifically quantifying HDL cholesterol in which cholesterol in lipoproteins other than HDL is erased in the first step, and HDL cholesterol is specifically quantified in the second step, by which accurate values can be obtained even in measurements of abnormal samples such as disorder of lipid metabolism and lipoprotein abnormality, is disclosed. The method for quantifying cholesterol in high density lipoprotein according to the present invention comprises a first step of erasing cholesterol in lipoproteins other than high density lipoprotein by treating a test sample with cholesterol esterase and cholesterol oxidase in the absence of a surfactant which acts on high density lipoprotein and removing generated hydrogen peroxide; and a second step of adding a surfactant which specifically acts on high density lipoprotein to the product of said first step and quantifying hydrogen peroxide generated from cholesterol in high density lipoprotein by actions of cholesterol esterase and cholesterol oxidase. As the cholesterol oxidase used in the first step, one having a molecular weight of not more than 60 kilodaltons is used.
1. Reagents for quantifying cholesterol in high density lipoprotein, comprising:
a first reagent consisting essentially of unmodified cholesterol esterase and cholesterol oxidase having a molecular weight of not more than 55.0 kilodaltons and a component which removes hydrogen peroxide; and
a second reagent comprising a surfactant which acts on high density lipoprotein,
wherein the first reagent does not contain a surfactant, which acts on high density lipoprotein.
2. The reagents according to claim 1 , wherein said component which removes hydrogen peroxide is catalase.
3. The reagents according to claim 1 , wherein said component which removes hydrogen peroxide is a phenol-based or aniline-based hydrogen donor compound which reacts with hydrogen peroxide to yield a colorless quinone.
4. The reagents according to claim 3 , wherein said phenol-based or aniline-based hydrogen donor compound is N-ethyl-N-(2-hydroxysulfopropyl)-3,5-dimethoxyaniline.
5. The reagents according to claim 1 , wherein said cholesterol oxidase has a molecular weight of 30 to 40 kilodaltons.