Gao R, Liu M, Chen Y, Xia C, Zhang H, Xiong Y, Huang S. Identification and characterization of human UDP-glucuronosyltransferases responsible for the in vitro glucuronidation of ursolic acid.
Drug Metab Pharmacokinet 2016;
31:261-8. [PMID:
27474355 DOI:
10.1016/j.dmpk.2015.11.010]
[Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 11/03/2015] [Accepted: 11/16/2015] [Indexed: 10/22/2022]
Abstract
This study aims to characterize the glucuronidation kinetics of ursolic acid (UA) in human liver microsomes (HLMs) and intestinal microsomes (HIMs) and identify the main UDP-glucuronosyltransferases (UGTs) involved. In our present study, only one type of UA glucuronide was observed after incubation with HLMs and HIMs respectively and was identified as a UA hydroxyl O-glucuronide. The glucuronidation of UA can be shown in HLMs and HIMs with Km values of 3.29 ± 0.16 and 3.74 ± 0.22 μM and Vmax values of 0.33 ± 0.03 and 0.42 ± 0.03 nmol/min/(mg protein). Among the 12 recombinant UGT enzymes investigated, UGT1A3 and UGT1A4 were identified as the major enzymes catalyzing the glucuronidation of UA [Km values of 2.58 ± 0.12 and 4.66 ± 0.60 μM, Vmax values of 0.72 ± 0.01 and 1.00 ± 0.06 nmol/min/(mg protein)]. The chemical inhibition study showed that the IC50 for hecogenin inhibition of UA glucuronidation was 51.79 ± 4.32 μM in HLMs. And chenodeoxycholic acid inhibited UA glucuronidation in HLMs with an IC50 of 28.26 ± 2.91 μM. In addition, UA glucuronidation in a panel of eight HLM was significantly correlated with telmisartan glucuronidation (r(2) = 0.7660, p < 0.01) and trifluoperazine glucuronidation (r(2) = 0.5866, p < 0.01) respectively. These findings collectively indicate that UGT1A3 and UGT1A4 were the main enzymes responsible for the glucuronidation of UA in human.
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