title: Metabolic profile, enzyme kinetics, and reaction phenotyping of β-lapachone metabolism in human liver and intestine in vitro.
abstract: β-Lapachone (β-Lap) is an
  quinone oxidoreductase 1 (NQO1) target antitumor drug candidate in phase II clinical trials. The present study aimed to uncover the metabolic profile, enzyme kinetics, and enzyme isoforms for the metabolism of β-Lap in human liver and intestine in vitro. NQO1-mediated quinone reduction and subsequent glucuronidation is the predominant metabolic pathway for β-Lap in humans; a pair of regioisomers (M1 and M2) of reduced β-Lap glucuronides were the major metabolites found from human S9 incubations. The overall glucuronidation clearance of β-Lap in human liver S9 was 4754.90 μL/min/mg of protein and was 8.1-fold of that in human intestinal S9. Recombinant UDP-glucuronosyltransferase (UGT) screening, correlation analysis, enzyme kinetics, and chemical inhibition study were performed to determine the UGT isoforms involved in β-Lap metabolism. UGT1A7, UGT1A8, and UGT1A9 are the predominant isoforms responsible for the formation of M2 while UGT2B7 is the main isoform for M1, suggesting a regioselective glucuronidation of reduced quinone by UGTs. It was of interest to find that β-Lap underwent nonenzymatic two-electron reduction, providing a novel explanation for the toxicities of β-Lap to NQO1-negative cells at high concentration and with long-time incubation. In conclusion, this study contributes to a better understanding of not only β-Lap metabolism but its antitumor property as well.
authors.affiliation: State Key Laboratory of Natural Medicines, Key Lab of Drug Metabolism and Pharmacokinetics, China Pharmaceutical University, Nanjing, China.
authors.forename: Xuefang
authors.initials: X
authors.lastname: Cheng
authors.forename: Fang
authors.initials: F
authors.lastname: Liu
authors.forename: Tingting
authors.initials: T
authors.lastname: Yan
authors.forename: Xueyan
authors.initials: X
authors.lastname: Zhou
authors.forename: Liang
authors.initials: L
authors.lastname: Wu
authors.forename: Ke
authors.initials: K
authors.lastname: Liao
authors.forename: Guangji
authors.initials: G
authors.lastname: Wang
authors.forename: Haiping
authors.initials: H
authors.lastname: Hao
mesh_terms: D020719:Glucuronides / Q000378:metabolism; D014453:Glucuronosyltransferase / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism*; D007527:Isoenzymes; D007700:Kinetics; D055442:Metabolome; D008862:Microsomes, Liver / Q000378:metabolism*; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000378:metabolism; D009285:Naphthoquinones / Q000378:metabolism*; D010641:Phenotype; D021241:Spectrometry, Mass, Electrospray Ionization; D000090264:UDP-Glucuronosyltransferase 1A9
chemical_list: D020719:Glucuronides; D007527:Isoenzymes; D009285:Naphthoquinones; C000715591:UGT1A9 protein, human; C014638:beta-lapachone; D016660:NAD(P)H Dehydrogenase (Quinone); C447479:NQO1 protein, human; D014453:Glucuronosyltransferase; D000090264:UDP-Glucuronosyltransferase 1A9; C454320:UDP-glucuronosyltransferase, UGT1A8; C524630:UGT1A7 protein, human