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. A method for quantifying cholesterol in high density lipoprotein, which comprises: (a) erasing cholesterol in lipoproteins other than high density lipoprotein by treating a test sample with cholesterol esterase and low molecular weight cholesterol oxidase in the absence of a surfactant which acts on high density lipoprotein and removing generated hydrogen peroxide; (b) adding a surfactant which specifically acts on high density lipoprotein to the product of step (a), and (c) quantifying hydrogen peroxide generated from cholesterol in the high density lipoprotein of step (b) by actions of cholesterol esterase and low molecular weight cholesterol oxidase; wherein said low molecular weight cholesterol oxidase has a molecular weight of not more than 55.0 kilodaltons.
2. The method according to claim 1 , wherein said low molecular weight cholesterol oxidase has a molecular weight of 30 to 40 kilodaltons.
3. The method according to claim 1 or 2 , wherein said surfactant which specifically acts on the high density lipoprotein has an hydrophilicity-lipophilicity balance (HLB) value of 13 to 14.
4. The method according to claim 3 , wherein said surfactant which specifically acts on the high density lipoprotein is a polyalkylene oxide derivative.