Characterization of Rat and Human UDP-Glucuronosyltransferases Responsible for the in Vitro Glucuronidation of Diclofenac
| Autor: | M. Braun, J. Ngui, W. Tang, C. King, T. Tephly |
|---|---|
| Rok vydání: | 2001 |
| Předmět: |
Male
UGT1A6 Diclofenac Statistics as Topic Glucuronidation In Vitro Techniques Pharmacology Toxicology Catalysis Mass Spectrometry Substrate Specificity Rats Sprague-Dawley Glucuronides medicine Animals Humans Toxicokinetics Enzyme kinetics Enzyme Inhibitors Glucuronosyltransferase chemistry.chemical_classification Morphine Chemistry Recombinant Proteins Rats Isoenzymes Kinetics stomatognathic diseases Enzyme UDP-Glucuronosyltransferase 1A9 Microsomes Liver Microsome Female Chromatography Liquid medicine.drug |
| Zdroj: | Toxicological Sciences. 61:49-53 |
| ISSN: | 1096-0929 |
| Popis: | In the current study, the identification of the rat and human UDP-glucuronosyltransferase (UGT) isoforms responsible for the glucuronidation of diclofenac was determined. Recombinant human UGT1A9 catalyzed the glucuronidation of diclofenac at a moderate rate of 166-pmol/min/mg protein, while UGT1A6 and 2B15 catalyzed the glucuronidation of diclofenac at low rates (20-pmol/min/mg protein). Conversely, human UGT2B7 displayed a high rate of diclofenac glucuronide formation (500 pmol/min/mg protein). Recombinant rat UGT2B1 catalyzed the glucuronidation of diclofenac at a rate of 250-pmol/min/mg protein. Rat UGT2B1 and human UGT2B7 displayed a similar, low apparent Km value of15 microM for both UGT isoforms and high Vmax values 0.3 and 2.8 nmol/min/mg, respectively. Using diclofenac as a substrate, enzyme kinetics in rat and human liver microsomes showed that the enzyme(s) involved in diclofenac glucuronidation had a low apparent Km value of20 microM and a high Vmax value of 0.9 and 4.3 nmol/min/mg protein, respectively. Morphine is a known substrate for rat UGT2B1 and human UGT2B7 and both total morphine glucuronidation (3-O- and 6-O-glucuronides) and diclofenac glucuronidation reactions showed a strong correlation with one another in human liver microsome samples. In addition, diclofenac inhibited the glucuronidation of morphine in human liver microsomes. These data suggested that rat UGT2B1 and human UGT2B7 were the major UGT isoforms involved in the glucuronidation of diclofenac. |
| Databáze: | OpenAIRE |
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