Open AccessThe Influence of Cholesterol Incorporation and Removal on Lipid‐Bilayer Viscosity and Electron Transfer in Rat‐Liver Microsomes
Author(s) -
ARCHAKOV Alexander I.,
BORODIN Evgeni A.,
DOBRETSOV Gennadi E.,
KARASEVICH Elena I.,
KARYAKIN Alexander V.
Publication year - 1983
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1983.tb07535.x
Subject(s) - chemistry , microsome , cytochrome b5 , cytochrome , hydroxylation , reaction rate constant , redox , dimethylaniline , bilayer , lipid bilayer , demethylation , photochemistry , viscosity , membrane , biochemistry , kinetics , organic chemistry , enzyme , physics , gene expression , quantum mechanics , dna methylation , gene
The incorporation and removal of cholesterol from rat liver microsomes was used as a methodical approach to investigate the molecular organization of microsomal redox‐chains. It was shown that the incorporation of cholesterol in microsomes increases and removal of cholesterol decreases lipid bilayer viscosity as indicated from the rate of fluorescent probe‐pyrene eximerisation in cholesterol‐enriched and cholesterol‐depleted microsomes. The increase of membrane viscosity slows down the initial rates and decreases the rate constants of cytochrome b 5 reduction by NAD(P)H, whereas the decrease of membrane viscosity enhances the initial rates and increases the rate constants of these reactions. The rates of cytochrome P450 reduction by reduced pyridine nucleotides do not depend on the viscosity of lipid bilayer. The incorporation and removal of cholesterol from microsomes was not followed by any essential changes in the rates of dimethylaniline N ‐demethylation, aniline p ‐hydroxylation, p ‐nitroanisole O ‐demethylation, oxygen consumption, oxidation of NADH and NADPH. Thus the reduction of cytochrome b 5 by NADH and NADPH is the diffusion‐dependent reaction in the redoxchains of microsomes only.