Estudo da ação de poliânions sobre a atividade das enzimas colesterol esterase e colesterol oxidase, utilizando lipoproteínas plasmáticas como substratos

Abstract

Sugiuchi et al. (1995) developed a direct method to determine cholesterol from high density lipoprotein, with no need for pre-analytical procedures. The assay consists of the formation apoB100-lipoproteins' soluble complexes with -cyclodextrin sulfate polyanion, which reduces the action of the enzymes cholesterol esterase and cholesterol oxidase over low density lipoprotein (LDL), very low density lipoprotein (VLDL) and chylomicra. Total inhibition of the enzymatic catalysis over apoB100-lipoproteins is achieved after the covalent bonding of polyethyleneglycol on the enzymes surfaces. Only the HDL's particles are available for the catalysis of cholesterol esterase and cholesterol oxidase. This study verified the inhibition of the reactions catalyzed by cholesterol esterase and cholesterol oxidase by the polyanions: phosphotungstic acid, sucrose octasulfate, chondroitin sulfate and - cyclodextrin sulfated. Kinetics parameters for the native enzyme cholesterol esterase and after the bonding with polyethyleneglycol were also determinate. The results showed that phosphotungstic acid is able to inhibit satisfactorily the enzymes' action over apoB100-lipoproteins. The Km's values for native cholesterol esterase with HDL and LDL were 4,26 M of cholesteryl linoleate and 13,14 M of cholesteryl linoleate, respectively. After the bound of polyethyleneglycol on the cholesterol esterase surface the enzimes Km for HDL was altered to 21,6 M of cholesteryl linoleate. The results of this study provide the knowledge to develop a reagent used to determine HDL cholesterol.