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Identification of the Human UDP-Glucuronosyltransferases Involved in the Glucuronidation of Combretastatin A-4

Identification of the Human UDP-Glucuronosyltransferases Involved in the Glucuronidation of... Abstract The stilbenic compound ( Z )-combretastatin A-4 (CA-4) has been described as a potent tubulin polymerization inhibitor. In vivo, CA-4 binds to tubulin and inhibits microtubule depolymerization, which results in morphological changes in proliferating endothelial cells. Combretastatin A-4 prodrug phosphate is a leading vascular disrupting agent and is currently being evaluated in multiple clinical trials as a treatment for solid tumors. The aim of this study was to identify and characterize the UDP-glucuronosyltransferase (UGT) isoforms involved in CA-4 glucuronidation by incubation with human liver microsomes and a panel of nine liver-expressed recombinant UGT Supersomes (1A1, 1A3, 1A4, 1A6, 1A9, 2B4, 2B7, 2B15, and 2B17). As we observed, the high rate of formation of CA-4 glucuronide ( V max = 12.78 ± 0.29 nmol/min/mg protein) and the low K m (6.98 ± 0.65 μM) denoted that UGT1A9 was primarily responsible for the in vitro glucuronidation of CA-4. UGT1A6 was also a significant contributor to CA-4 glucuronidation ( V max = 3.95 ± 0.13 nmol/min/mg protein and S 50 = 44.80 ± 3.54 μM). Furthermore, we demonstrated that the kinetics of CA-4 glucuronidation with liver microsomes but also with a panel of recombinant UGTs is atypical as it fits two different models: the substrate inhibition and also the sigmoidal kinetic model. Finally, experiments conducted to inhibit the glucuronosyltransferase activity in the human liver microsomes assay showed that phenylbutazone, trifluoperazine, propofol, and 1-naphthol effectively inhibited CA-4 glucuronidation. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Drug Metabolism and Disposition Am. Soc for Pharma & Experimental Therapeutics

Identification of the Human UDP-Glucuronosyltransferases Involved in the Glucuronidation of Combretastatin A-4

Identification of the Human UDP-Glucuronosyltransferases Involved in the Glucuronidation of Combretastatin A-4

Drug Metabolism and Disposition , Volume 38 (7): 1141 – Jul 1, 2010

Abstract

Abstract The stilbenic compound ( Z )-combretastatin A-4 (CA-4) has been described as a potent tubulin polymerization inhibitor. In vivo, CA-4 binds to tubulin and inhibits microtubule depolymerization, which results in morphological changes in proliferating endothelial cells. Combretastatin A-4 prodrug phosphate is a leading vascular disrupting agent and is currently being evaluated in multiple clinical trials as a treatment for solid tumors. The aim of this study was to identify and characterize the UDP-glucuronosyltransferase (UGT) isoforms involved in CA-4 glucuronidation by incubation with human liver microsomes and a panel of nine liver-expressed recombinant UGT Supersomes (1A1, 1A3, 1A4, 1A6, 1A9, 2B4, 2B7, 2B15, and 2B17). As we observed, the high rate of formation of CA-4 glucuronide ( V max = 12.78 ± 0.29 nmol/min/mg protein) and the low K m (6.98 ± 0.65 μM) denoted that UGT1A9 was primarily responsible for the in vitro glucuronidation of CA-4. UGT1A6 was also a significant contributor to CA-4 glucuronidation ( V max = 3.95 ± 0.13 nmol/min/mg protein and S 50 = 44.80 ± 3.54 μM). Furthermore, we demonstrated that the kinetics of CA-4 glucuronidation with liver microsomes but also with a panel of recombinant UGTs is atypical as it fits two different models: the substrate inhibition and also the sigmoidal kinetic model. Finally, experiments conducted to inhibit the glucuronosyltransferase activity in the human liver microsomes assay showed that phenylbutazone, trifluoperazine, propofol, and 1-naphthol effectively inhibited CA-4 glucuronidation.

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References (21)

Publisher
Am. Soc for Pharma & Experimental Therapeutics
Copyright
Copyright © Drug Metabolism and Disposition
ISSN
0090-9556
eISSN
1521-009X
DOI
10.1124/dmd.109.031435
pmid
20375181
Publisher site
See Article on Publisher Site

Abstract

Abstract The stilbenic compound ( Z )-combretastatin A-4 (CA-4) has been described as a potent tubulin polymerization inhibitor. In vivo, CA-4 binds to tubulin and inhibits microtubule depolymerization, which results in morphological changes in proliferating endothelial cells. Combretastatin A-4 prodrug phosphate is a leading vascular disrupting agent and is currently being evaluated in multiple clinical trials as a treatment for solid tumors. The aim of this study was to identify and characterize the UDP-glucuronosyltransferase (UGT) isoforms involved in CA-4 glucuronidation by incubation with human liver microsomes and a panel of nine liver-expressed recombinant UGT Supersomes (1A1, 1A3, 1A4, 1A6, 1A9, 2B4, 2B7, 2B15, and 2B17). As we observed, the high rate of formation of CA-4 glucuronide ( V max = 12.78 ± 0.29 nmol/min/mg protein) and the low K m (6.98 ± 0.65 μM) denoted that UGT1A9 was primarily responsible for the in vitro glucuronidation of CA-4. UGT1A6 was also a significant contributor to CA-4 glucuronidation ( V max = 3.95 ± 0.13 nmol/min/mg protein and S 50 = 44.80 ± 3.54 μM). Furthermore, we demonstrated that the kinetics of CA-4 glucuronidation with liver microsomes but also with a panel of recombinant UGTs is atypical as it fits two different models: the substrate inhibition and also the sigmoidal kinetic model. Finally, experiments conducted to inhibit the glucuronosyltransferase activity in the human liver microsomes assay showed that phenylbutazone, trifluoperazine, propofol, and 1-naphthol effectively inhibited CA-4 glucuronidation.

Journal

Drug Metabolism and DispositionAm. Soc for Pharma & Experimental Therapeutics

Published: Jul 1, 2010

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