Structural Biochemistry/Drug regulation enzymes

Drug metabolism can occur in every tisuue, however the major drug metabolizing enzymes( DMEs) are ezpressed at the highest levels in the liver. Drug metabolism serves to control the exposure of a potentially harmful substance. DMEs also help to regulate endogenous function.

CYP3A4 is a drug-metabolizing enzyme in the intestines that increases or alters blood vessels of certain medications in people.

Cytochrome P450(CYP459)
CYP450 named based on its light absorption at 450nm when completed with carbon monoxide.It is a cytochrome enzyme that processes essential molecules such as hormones and vitamins as well as metabolize hundreds of prescribed medicines and natural substances. It is a "super family" of enzyme with a very broad substrate selectivity.CYP450 is based on shared homology of amino acid sequence. Drug metabolism: the cycle involves four steps

1. Oxidized (Fe3+) CYP450 combines with a drug substrate to form a binary complex.

2. NADPH donates an electron to the CYP450 reductase, which turn reduces the oxidized CYP450 drug complex.

3. A second electron is introduced from NADPH via the same CYP450 reductase, which serves to reduce molecular oxygen and form an" activated oxygen"-CYP450 substrate complex.

4. This complex in turn transfers" activated" oxygen to the drug substrate to form the oxidized product. The potent oxidizing properties of this activated oxygen permit oxidation of a large number of substrates.

Source: Davis, Alison. (2006). Medicines By Design. National Institutes of Health, 8.