1013074-93-5Relevant articles and documents
Identification of human UGT2B7 as the major isoform involved in the O-glucuronidation of chloramphenicol
Chen, Mei,LeDuc, Barbara,Kerr, Stephen,Howe, David,Williams, David A.
, p. 368 - 375 (2010)
Chloramphenicol (CP), a broad spectrum antibiotic, is eliminated in humans by glucuronidation. The primary UGT enzymes responsible for CP O-glucuronidation remain unidentified. We have previously identified the 3-O-CP (major) and 1-O-CP (minor) glucuronides by β-glucuronidase hydrolysis, liquid chromatography-tandem mass spectrometry, and 1D/2D H NMR. Reaction phenotyping for the glucuronidation of CP with 12 expressed human liver UGT isoforms has identified UGT2B7 as having the highest activity for 3-O- and 1-O-CP glucuronidation with minor contributions from UGT1A6 and UGT1A9. The kinetics of CP 3-O-glucuronidation by pooled human liver microsomes (HLMs) exhibited biphasic Michaelis-Menten kinetics with the apparent high-affinity K m1 and low-affinity Km2 values of 46.0 and 1027 μM, whereas expressed UGT2B7 exhibited Michaelis-Menten kinetics with the apparent Km value of 109.1 μM. The formation of 1-O-CP glucuronide by pooled HLM and expressed UGT2B7 exhibited substrate inhibition kinetics with apparent Km values of 408.2 and 115.0 μM, respectively. Azidothymidine (AZT) and hyodeoxycholic acid (substrates of UGT2B7) inhibited 3-O- and 1-O-CP glucuronidation in pooled HLMs. In 10 donor HLM preparations, both CP 3-O- and CP 1-O-glucuronidation showed a significant correlation with AZT glucuronidation (UGT2B7) (rs = 0.85 and rs = 0.83, respectively) at 30 μMCP, whereas no significant correlation was observed between CP 3-O-glucuronidation and serotonin glucuronidation (UGT1A6) or propofol glucuronidation (UGT1A9) at this CP concentration. These results suggest that UGT2B7 is the primary human hepatic UDP-glucuronosyltransferase isoform catalyzing 3-O- and 1-O-CP glucuronidation with minor contributions from UGT1A6 and UGT1A9. Copyright
