Acyl glucuronidation of fluoroquinolone antibiotics by the UDP-glucuronosyltransferase 1A subfamily in human liver microsomes. 2005

Masaya Tachibana, and Makoto Tanaka, and Yasuhiro Masubuchi, and Toshiharu Horie
Department of Biopharmaeutics, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba, Japan. tachi6nx@daiichipharm.co.jp

Acyl glucuronidation is an important metabolic pathway for fluoroquinolone antibiotics. However, it is unclear which human UDP-glucuronosyltransferase (UGT) enzymes are involved in the glucuronidation of the fluoroquinolones. The in vitro formation of levofloxacin (LVFX), grepafloxacin (GPFX), moxifloxacin (MFLX), and sitafloxacin (STFX) glucuronides was investigated in human liver microsomes and cDNA-expressed recombinant human UGT enzymes. The apparent Km values for human liver microsomes ranged from 1.9 to 10.0 mM, and the intrinsic clearance values (calculated as Vmax/Km) had a rank order of MFLX > GPFX > STFX > > LVFX. In a bank of human liver microsomes (n = 14), the glucuronidation activities of LVFX, MFLX, and STFX correlated highly with UGT1A1-selective beta-estradiol 3-glucuronidation activity, whereas the glucuronidation activity of GPFX correlated highly with UGT1A9-selective propofol glucuronidation activity. Among 12 recombinant UGT enzymes, UGT1A1, 1A3, 1A7, and 1A9 catalyzed the glucuronidation of these fluoroquinolones. Results of enzyme kinetics studies using the recombinant UGT enzymes indicated that UGT1A1 most efficiently glucuronidates MFLX, and UGT1A9 most efficiently glucuronidates GPFX. In addition, the glucuronidation activities of MFLX and STFX in human liver microsomes were potently inhibited by bilirubin with IC50 values of 4.9 microM and 4.7 microM, respectively; in contrast, the glucuronidation activity of GPFX was inhibited by mefenamic acid with an IC50 value of 9.8 microM. These results demonstrate that UGT1A1, 1A3, and 1A9 enzymes are involved in the glucuronidation of LVFX, GPFX, MFLX, and STFX in human liver microsomes, and that MFLX and STFX are predominantly glucuronidated by UGT1A1, whereas GPFX is mainly glucuronidated by UGT1A9.

UI MeSH Term Description Entries
D008297 Male Males
D008862 Microsomes, Liver Closed vesicles of fragmented endoplasmic reticulum created when liver cells or tissue are disrupted by homogenization. They may be smooth or rough. Liver Microsomes,Liver Microsome,Microsome, Liver
D004305 Dose-Response Relationship, Drug The relationship between the dose of an administered drug and the response of the organism to the drug. Dose Response Relationship, Drug,Dose-Response Relationships, Drug,Drug Dose-Response Relationship,Drug Dose-Response Relationships,Relationship, Drug Dose-Response,Relationships, Drug Dose-Response
D005810 Multigene Family A set of genes descended by duplication and variation from some ancestral gene. Such genes may be clustered together on the same chromosome or dispersed on different chromosomes. Examples of multigene families include those that encode the hemoglobins, immunoglobulins, histocompatibility antigens, actins, tubulins, keratins, collagens, heat shock proteins, salivary glue proteins, chorion proteins, cuticle proteins, yolk proteins, and phaseolins, as well as histones, ribosomal RNA, and transfer RNA genes. The latter three are examples of reiterated genes, where hundreds of identical genes are present in a tandem array. (King & Stanfield, A Dictionary of Genetics, 4th ed) Gene Clusters,Genes, Reiterated,Cluster, Gene,Clusters, Gene,Families, Multigene,Family, Multigene,Gene Cluster,Gene, Reiterated,Multigene Families,Reiterated Gene,Reiterated Genes
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D001663 Bilirubin A bile pigment that is a degradation product of HEME. Bilirubin IX alpha,Bilirubin, (15E)-Isomer,Bilirubin, (4E)-Isomer,Bilirubin, (4E,15E)-Isomer,Bilirubin, Calcium Salt,Bilirubin, Disodium Salt,Bilirubin, Monosodium Salt,Calcium Bilirubinate,Hematoidin,delta-Bilirubin,Bilirubinate, Calcium,Calcium Salt Bilirubin,Disodium Salt Bilirubin,Monosodium Salt Bilirubin,Salt Bilirubin, Calcium,delta Bilirubin
D014453 Glucuronosyltransferase A family of enzymes accepting a wide range of substrates, including phenols, alcohols, amines, and fatty acids. They function as drug-metabolizing enzymes that catalyze the conjugation of UDPglucuronic acid to a variety of endogenous and exogenous compounds. EC 2.4.1.17. Glucuronyltransferase,UDP Glucuronosyltransferase,17 beta-Hydroxysteroid UDP-Glucuronosyltransferase,4-Nitrophenol-UDP-Glucuronosyltransferase,7-Hydroxycoumarin UDP Glucuronyltransferase,Androsterone UDP-Glucuronosyltransferase,Bilirubin UDP-Glucuronyltransferase,Estrogen UDP-Glucuronosyltransferase,Estrone Glucuronyltransferase,Glucuronic Transferase,Morphine Glucuronyltransferase,UDP Glucuronyl Transferase,UDP-Glucuronic Acid 3-O-beta-D-Galactosyl-D-Galactose Glucuronosyltransferase,p-Nitrophenyl UDP-Glucuronosyltransferase,17 beta Hydroxysteroid UDP Glucuronosyltransferase,4 Nitrophenol UDP Glucuronosyltransferase,7 Hydroxycoumarin UDP Glucuronyltransferase,Androsterone UDP Glucuronosyltransferase,Bilirubin UDP Glucuronyltransferase,Estrogen UDP Glucuronosyltransferase,Glucuronosyltransferase, UDP,Glucuronyl Transferase, UDP,Glucuronyltransferase, 7-Hydroxycoumarin UDP,Glucuronyltransferase, Estrone,Glucuronyltransferase, Morphine,Transferase, Glucuronic,Transferase, UDP Glucuronyl,UDP Glucuronic Acid 3 O beta D Galactosyl D Galactose Glucuronosyltransferase,UDP Glucuronyltransferase, 7-Hydroxycoumarin,UDP-Glucuronosyltransferase, 17 beta-Hydroxysteroid,UDP-Glucuronosyltransferase, Androsterone,UDP-Glucuronosyltransferase, Estrogen,UDP-Glucuronosyltransferase, p-Nitrophenyl,UDP-Glucuronyltransferase, Bilirubin,p Nitrophenyl UDP Glucuronosyltransferase
D017207 Rats, Sprague-Dawley A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company. Holtzman Rat,Rats, Holtzman,Sprague-Dawley Rat,Rats, Sprague Dawley,Holtzman Rats,Rat, Holtzman,Rat, Sprague-Dawley,Sprague Dawley Rat,Sprague Dawley Rats,Sprague-Dawley Rats
D051381 Rats The common name for the genus Rattus. Rattus,Rats, Laboratory,Rats, Norway,Rattus norvegicus,Laboratory Rat,Laboratory Rats,Norway Rat,Norway Rats,Rat,Rat, Laboratory,Rat, Norway,norvegicus, Rattus

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