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Microsomal redox systems in brown adipose tissue: high lipid peroxidation, low cholesterol biosynthesis and no detectable cytochrome P-450

Sekhar, Seshadri B and Kurup, Ramakrishna CK and Ramasarma, T (1990) Microsomal redox systems in brown adipose tissue: high lipid peroxidation, low cholesterol biosynthesis and no detectable cytochrome P-450. In: Molecular and Cellular Biochemistry, 92 (2). pp. 147-157.

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Abstract

The presence of redox systems in microsomes of brown adipose tissue (BAT) in cold exposed rats was investigated and compared with liver. BAT microsomes showed high activity of lipid peroxidation measured both by the formation of malondialdehyde (MDA) and by oxygen uptake. NADH and NADPH dependent cytochrome c reductase activity were present in both BAT and liver microsomes. Aminopyrine demethylase and aniline hydroxylase activities, the characteristic detoxification enzymes in liver microsomes could not be detected in BAT microsomes. BAT minces showed very poor incorporation of [1-14C]acetate and [2-14C]-mevalonate in unsaponifiable lipid fraction compared to liver. Biosynthesis of cholesterol and ubiquinone, but not fatty acids, and the activity of 3-hydroxy-3-methyl glutaryl CoA reductase appear to be very low in BAT. Examination of difference spectra showed the presence of only cytochrome b 5 in BAT microsomes. In addition to the inability to detect the enzyme activities dependent on cytochrome P-450, a protein with the characteristic spectrum, molecular size in SDS-PAGE and interaction with antibodies in double diffusion test, also could not be detected in BAT microsomes. The high activity of lipid peroxidation in microsomes, being associated with large oxygen uptake and oxidation of NADPH, will also contribute to the energy dissipation as heat in BAT, considered important in thermogenesis.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Springer.
Keywords: microsomal redox systems;brown adipose tissue;lipid peroxidation;cholesterol biosynthesis;cytochrome P-450
Department/Centre: Division of Biological Sciences > Biochemistry
Depositing User: Ms TV Yashodha
Date Deposited: 27 Apr 2011 05:02
Last Modified: 27 Apr 2011 05:02
URI: http://eprints.iisc.ac.in/id/eprint/35036

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