title: Identification and characterization of human UDP-glucuronosyltransferases responsible for the in vitro glucuronidation of ursolic acid.
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.
authors.affiliation: Clinical Pharmacology Institute, Nanchang University, Nanchang, 330006, PR China; Peking University Binhai Hospital (Tianjin Fifth Center Hospital), Tianjin, 300450, PR China.
authors.forename: Rui
authors.initials: R
authors.lastname: Gao
authors.affiliation: Clinical Pharmacology Institute, Nanchang University, Nanchang, 330006, PR China.
authors.forename: Mingyi
authors.initials: M
authors.lastname: Liu
authors.affiliation: Clinical Pharmacology Institute, Nanchang University, Nanchang, 330006, PR China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Clinical Pharmacology Institute, Nanchang University, Nanchang, 330006, PR China. Electronic address: xch720917@163.com.
authors.forename: Chunhua
authors.initials: C
authors.lastname: Xia
authors.affiliation: Clinical Pharmacology Institute, Nanchang University, Nanchang, 330006, PR China.
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Clinical Pharmacology Institute, Nanchang University, Nanchang, 330006, PR China.
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Xiong
authors.affiliation: Clinical Pharmacology Institute, Nanchang University, Nanchang, 330006, PR China.
authors.forename: Shibo
authors.initials: S
authors.lastname: Huang
mesh_terms: D020723:Glucuronic Acid / Q000378:metabolism; D014453:Glucuronosyltransferase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007422:Intestines / Q000201:enzymology; D008861:Microsomes / Q000201:enzymology; D008862:Microsomes, Liver / Q000201:enzymology; D011994:Recombinant Proteins / Q000378:metabolism; D014315:Triterpenes / Q000737:chemistry / Q000378:metabolism*; D000097245:Ursolic Acid
chemical_list: D020723:Glucuronic Acid; D014453:Glucuronosyltransferase; D011994:Recombinant Proteins; D014315:Triterpenes; D000097245:Ursolic Acid
keywords: Metabolism characterization; Metabolism pathway; UDP-glucuronosyltransferases; Ursolic acid