Table 1.
Examples of drug metabolizing enzymes (DMEs) [17].
| Classification | Enzymes | Overall reactions |
|---|---|---|
| Oxidative DMEs (Phase I reactions) | Cytochrome P450 (CYP450) | Carbon oxidation RH + O2 + NADPH + H+→ ROH + H2O + NADP+ |
| Flavin-containing monooxygenase (FMO) | N (or S) oxidation R-NH-R′ + O2 + NADPH + H+→ R-NOH-R′ + H2O + NADP+ | |
| Monoamine oxidase (MAO) | Oxidative deamination R-CH2NH2 + O2 + H2O → R-CHO + H2O2 + NH3 | |
| Alcohol dehydrogenase | Alcohol oxidation R-CH2OH + NAD+→ R-CHO + NADH + H+ | |
| Aldehyde dehydrogenase | Aldehyde oxidation R-CHO + NAD(P)+ + H2O → R-COOH + NAD(P)H + H+ | |
| Aldehyde oxidase | Aldehyde oxidation R-CHO + O2 + H2O → R-COOH + H2O2 | |
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| Conjugative DMEs (Phase II reactions) | UDP-glycosyltransferase (UGT) | Glucuronidation R + UDP-glucuronic acid → R-glucuronide + UDP |
| Glutathione S-transferase (GST) | Glutathione conjugation R + GSH → GS-RR-X + GSH → GS-R + HX | |
| Sulfotransferase (SULT) | Sulfation R-XH + PAPS → R-SO4 + phosphoadenosine + H+ | |
| N-Acetyltransferase (NAT) | Methylation R-NH2 + CoA-S-COCH3→ R-NCOCH3 + CoA-SHR-NHOH + CoA-S-COCH3→ R-NHOCOCH3 + CoA-SH | |
Xenobiotics (R), β-nicotinamide adenine dinucleotide phosphate (NADP), β-nicotinamide adenine dinucleotide (NAD), uridine 5′-diphosphate (UDP), glutathione (GSH), 3′-phosphoadenosine 5′-phosphosulfate (PAPS), and coenzyme A (CoA).