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| Comparative metabolic capabilities of CYP3A4, CYP3A5, and CYP3A7 |
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| Author(s): Williams JA, Ring BJ, Cantrell VE, Jones DR, Eckstein J, Ruterbories K, Hamman MA, Hall SD, Wrighton SA |
| Source: DRUG METABOLISM AND DISPOSITION Volume: 30 Issue: 8 Pages: 883-891 Published: AUG 2002 |
| Times Cited: 90 References: 32 |
| Abstract: The human cytochromes P450 (P450) CYP3A contribute to the biotransformation of 50% of oxidatively metabolized drugs. The predominant hepatic form is CYP3A4, but recent evidence indicates that CYP3A5 contributes more significantly to the total liver CYP3A than was originally thought. CYP3A7 is the major fetal form and is rarely expressed in adults. To compare the metabolic capabilities of CYP3A forms for 10 substrates, incubations were performed using a consistent molar ratio (1: 7: 9) of recombinant CYP3A, P450 reductase, and cytochrome b5. A wide range of substrate concentrations was examined to determine the best fit to kinetic models for metabolite formation. In general, K-m or S-50 values for the substrates were 3 to 4 times lower for CYP3A4 than for CYP3A5 or CYP3A7. For a more direct comparison of these P450 forms, clearance to the metabolites was determined as a linear relationship of rate of metabolite formation for the lowest substrate concentrations examined. The clearance for 1'-hydroxy midazolam formation at low substrate concentrations was similar for CYP3A4 and CYP3A5. For CYP3A5 versus CYP3A4, clearance values at low substrate concentrations were 2 to 20 times lower for the other biotransformations. The clearance values for CYP3A7-catalyzed metabolite formation at low substrate concentrations were substantially lower than for CYP3A4 or CYP3A5, except for clarithromycin, 4-OH triazolam, and N-desmethyl diltiazem (CYP3A5 approximate to CYP3A7). The CYP3A forms demonstrated regioselective differences in some of the biotransformations. These results demonstrate an equal or reduced metabolic capability for CYP3A5 compared with CYP3A4 and a significantly lower capability for CYP3A7. |
| Document Type: Article |
| Language: English |
| Reprint Address: Wrighton, SA (reprint author), Eli Lilly & Co, Lilly Res Labs, Dept Drug Disposit, Drop Code 0710, Indianapolis, IN 46285 USA |
Addresses:
1. Eli Lilly & Co, Lilly Res Labs, Dept Drug Disposit, Indianapolis, IN 46285 USA
2. Indiana Univ, Sch Med, Dept Clin Pharmacol, Indianapolis, IN 46204 USA |
| Publisher: AMER SOC PHARMACOLOGY EXPERIMENTAL THERAPEUTICS, 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA |
| Subject Category: Pharmacology & Pharmacy |
| IDS Number: 574GB |
| ISSN: 0090-9556 |
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| | | | | | | | | Record from Web of Science® | | | | | | | | | |