Several enzymatic systems are involved during the oxidative
transformations of xenobiotics. Whether substances
act upon one enzyme rather than another depends not only
on its specifi c function, but also on the electromolecular
environment. The most important is the microsomal drug
metabolizing system known as cytochrome P450 (CYP)
monooxygenase, which is localized mainly in the liver
and is involved in most biological oxidations of xenobiotics.
7–9 Those include C- , N- and S- oxidations, N- , O- and
S- dealkylation, deaminations, and certain dehalogenations.
Under anaerobic conditions, it can also catalyze reductive
reactions. The CYP monooxygenase system is a multienzymatic
complex constituted by the CYP hemoprotein,
the fl avoprotein enzyme NADPH CYP reductase, and the
unsaturated phospholipid phosphatidylcholine. The isoforms
involved in xenobiotic metabolism are membrane
bound enzymes situated in the endoplasmic reticulum
Several enzymatic systems are involved during the oxidativetransformations of xenobiotics. Whether substancesact upon one enzyme rather than another depends not onlyon its specifi c function, but also on the electromolecularenvironment. The most important is the microsomal drugmetabolizing system known as cytochrome P450 (CYP)monooxygenase, which is localized mainly in the liverand is involved in most biological oxidations of xenobiotics.7–9 Those include C- , N- and S- oxidations, N- , O- andS- dealkylation, deaminations, and certain dehalogenations.Under anaerobic conditions, it can also catalyze reductivereactions. The CYP monooxygenase system is a multienzymaticcomplex constituted by the CYP hemoprotein,the fl avoprotein enzyme NADPH CYP reductase, and theunsaturated phospholipid phosphatidylcholine. The isoformsinvolved in xenobiotic metabolism are membranebound enzymes situated in the endoplasmic reticulum
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