Archive

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Med. Pr. 2000;(14)

The system of ctochrome P450-dependent monooxygenases in metabolism of xenobiotics and endogenous products

Układ monooksygenaz zależnych od ctochromu P450 w metabolizacji ksenobiotyków i endogennych produktów przemian

M. Kamiński, R. Wiaderkiewicz, M. Orschulik

Abstract

Cytochrome P450-dependent monooxygenases are products of CYP450 gene superfamily whose evolution began some three billion years ago. Mammalian cytochromes P450 are membrane bound enzymes. They are located mostly in microsomes, but also in plasma membrane, nuclear membrane and mitochondria. Mitochondrial izoforms are involved primarily in metabolism of endogenous substrates, while those located in microsomes are responsible for metabolism of exogenous substrates, which are key enzymes of xenobiotic biotransformation phase I. Activity of cytochrome P450 depends on interaction with other proteins - donors of electrons in its catalytic cycle, like NADPH reductase and cytochrome b₅.
This paper describes the major components of the P450 system, their cellular and organ localization, as well as possible mechanisms of induction of izoforms CYP450 involved in the biotransformation of xenobiotics.

Key words

cytochrome P450, xenobiotic metabolism, biotransformation