Udp-glucuronosyltransferase 2b7 is the major enzyme responsible for gemcabene glucuronidation in human liver microsomes. 2005

Jonathan N Bauman, and Theunis C Goosen, and Meera Tugnait, and Vincent Peterkin, and Susan I Hurst, and Lee C Menning, and Mark Milad, and Michael H Court, and J Andrew Williams
Department of Pharmacokinetics, Dynamics and Metabolism, Pfizer Global Research and Development, Ann Arbor, MI 48105, USA. jonathan.bauman@pfizer.com.

The predominant metabolic pathway of gemcabene in humans is glucuronidation. The principal human UDP-glucuronosyltransferases (UGTs) involved in the glucuronidation of gemcabene were determined in this study. Glucuronidation of gemcabene was catalyzed by recombinant UGT1A3, recombinant UGT2B7, and recombinant UGT2B17, as well as by human liver microsomes (HLM). Gemcabene glucuronidation in recombinant UGTs and HLM followed non-Michaelis-Menten kinetics consistent with homotropic activation, but pharmacokinetics in humans were linear over the dose range tested (total plasma C(max), 0.06-0.88 mM). Gemcabene showed similar affinity (S(50)) for recombinant UGTs (0.92-1.45 mM) and HLM (1.37 mM). S-Flurbiprofen was identified as a more selective inhibitor of recombinant UGT2B7-catalyzed gemcabene glucuronidation (>23-fold lower IC(50)) when compared with recombinant UGT1A3- or recombinant UGT2B17-catalyzed gemcabene glucuronidation. The IC(50) for S-flurbiprofen inhibition of gemcabene glucuronidation was similar in HLM (60.6 microM) compared with recombinant UGT2B7 (27.4 microM), consistent with a major role for UGT2B7 in gemcabene glucuronidation in HLM. In addition, 5,6,7,3',4',5'-hexamethoxyflavone inhibited recombinant UGT1A3 and recombinant UGT2B17-catalyzed gemcabene glucuronidation (with 4-fold greater potency for recombinant UGT1A3) but did not inhibit gemcabene glucuronidation in HLM, suggesting that UGT1A3 and UGT2B17 do not contribute significantly to gemcabene glucuronidation. Reaction rates for gemcabene glucuronidation from a human liver bank correlated well (r(2)=0.722, P<0.0001; n=24) with rates of glucuronidation of the UGT2B7 probe substrate 3'-azido-3'-deoxythymidine. In conclusion, using the three independent experimental approaches typically used for cytochrome P450 reaction phenotyping, UGT2B7 is the major enzyme contributing to gemcabene glucuronidation in human liver microsomes.

UI MeSH Term Description Entries
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
D010641 Phenotype The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment. Phenotypes
D011994 Recombinant Proteins Proteins prepared by recombinant DNA technology. Biosynthetic Protein,Biosynthetic Proteins,DNA Recombinant Proteins,Recombinant Protein,Proteins, Biosynthetic,Proteins, Recombinant DNA,DNA Proteins, Recombinant,Protein, Biosynthetic,Protein, Recombinant,Proteins, DNA Recombinant,Proteins, Recombinant,Recombinant DNA Proteins,Recombinant Proteins, DNA
D002208 Caproates Derivatives of caproic acid. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain a carboxy terminated six carbon aliphatic structure. Hexanoates,Caproic Acid Derivatives,Caproic Acids,Hexanoic Acid Derivatives,Hexanoic Acids,Acid Derivatives, Caproic,Acid Derivatives, Hexanoic,Acids, Caproic,Acids, Hexanoic,Derivatives, Caproic Acid,Derivatives, Hexanoic Acid
D002478 Cells, Cultured Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others. Cultured Cells,Cell, Cultured,Cultured Cell
D004791 Enzyme Inhibitors Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction. Enzyme Inhibitor,Inhibitor, Enzyme,Inhibitors, Enzyme
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
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
D015215 Zidovudine A dideoxynucleoside compound in which the 3'-hydroxy group on the sugar moiety has been replaced by an azido group. This modification prevents the formation of phosphodiester linkages which are needed for the completion of nucleic acid chains. The compound is a potent inhibitor of HIV replication, acting as a chain-terminator of viral DNA during reverse transcription. It improves immunologic function, partially reverses the HIV-induced neurological dysfunction, and improves certain other clinical abnormalities associated with AIDS. Its principal toxic effect is dose-dependent suppression of bone marrow, resulting in anemia and leukopenia. AZT (Antiviral),Azidothymidine,3'-Azido-2',3'-Dideoxythymidine,3'-Azido-3'-deoxythymidine,AZT Antiviral,AZT, Antiviral,BW A509U,BWA-509U,Retrovir,3' Azido 2',3' Dideoxythymidine,3' Azido 3' deoxythymidine,Antiviral AZT,BWA 509U,BWA509U
D015778 Minor Histocompatibility Antigens Allelic alloantigens often responsible for weak graft rejection in cases when (major) histocompatibility has been established by standard tests. In the mouse they are coded by more than 500 genes at up to 30 minor histocompatibility loci. The most well-known minor histocompatibility antigen in mammals is the H-Y antigen. Histocompatibility Antigens, Minor,Minor Histocompatibility Antigen,Minor Histocompatibility Peptide,Minor Histocompatibility Peptides,Antigen, Minor Histocompatibility,Histocompatibility Antigen, Minor,Histocompatibility Peptide, Minor,Histocompatibility Peptides, Minor,Peptide, Minor Histocompatibility

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