PMID: 42250Jan 1, 1979

Mechanistic studies with purified components of the liver microsomal hydroxylation system: spectral intermediates in reaction of cytochrome P-450 with peroxy compounds

Acta biologica et medica Germanica
M J CoonD P Ballou

Abstract

Recent investigations in this laboratory on the mechanism of action of liver microsomal cytochrome P-450 (P-450 LM) and its interaction with other components of the hydroxylation system are presented. Two electrophoretically homogeneous forms of the cytochrome, phenobarbital-inducible P-450 LM2 and 5,6-benzoflavone-inducible P-450 LM4, so designated according to their relative electrophoretic mobilities, were used in these studies. Phosphatidylcholine is required in the reconstituted enzyme system for rapid electron transfer from NADPH to P-450 LM, catalyzed by NADPH-cytochrome P-450 reductase, as well as for maximal hydroxylation activity with either molecular oxygen or a peroxy compound serving as oxygen donor to the substrate. The phospholipid facilitates the binding of both substrate and reductase to P-450 LM and apparently causes a structural change in the cytochrome as shown by an increase in alpha-helical content, determined by circular dichroic spectrometry. P-450LM3 and LM4 are one-electron acceptors under anaerobic conditions, in accord with previous potentiometric titrations and product yield data, but in disagreement with previous titrations with reducing agents. The cause for the discrepancy between the present and...Continue Reading

Related Concepts

Anaerobiosis
Benzoflavones
Cytochrome P-450 Oxygenase
Respiratory Chain
Hydroxylation
Microsomes, Liver
NADP
Oxidation-Reduction
Peroxides
Luminal

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