Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.31 (beta-glucuronidase)
 7,680 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of adjuvant-induced arthritis on hepatic microsomal glucuronidation was studied in the rat. Arthritis was induced by injection of Mycobacterium butyricum suspended in liquid paraffin. Vmax and the Michaelis-Menten constant values for the in vitro glucuronidation of R- and S-ketoprofen, acetaminophen, and diflunisal by liver microsomes obtained from control and adjuvant-induced arthritic rats were compared. In addition, uridine 5'-diphosphate-glucuronosyltransferase activity toward bilirubin and p-nitrophenol, as well as levels of cytochrome P-450 and beta-glucuronidase were determined in these microsomal preparations. Adjuvant-induced arthritis resulted in a significant reduction in hepatic cytochrome P-450 levels and in p-nitrophenol glucuronidation (5.65 +/- 0.40 versus 2.58 +/- 0.27 micromol.min/mg protein in control and arthritic rats, respectively, mean +/- S.E.M.). Glucuronidation of bilirubin and beta-glucuronidase activities in liver microsomes and in plasma were not affected by adjuvant-induced arthritis. Vmax (nmol/min/mg protein) for the formation of R-ketoprofen glucuronide, S-ketoprofen glucuronide, diflunisal phenolic glucuronide, and diflunisal acyl glucuronide was significantly decreased in arthritic rats (0.68 +/- 0.10, 0.77 +/- 0. 12, 0.044 +/- 0.005, 0.26 +/- 0.03, respectively) compared with control rats (1.45 +/- 0.04, 1.60 +/- 0.04, 0.087 +/- 0.008, 0.46 +/- 0.04, respectively). Glucuronidation of p-nitrophenol, ketoprofen and diflunisal, substrates which seem to be at least partly glucuronidated in the rat by isoenzymes of the UGT2B subfamily, was impaired in adjuvant-induced arthritis. Glucuronidation of bilirubin and acetaminophen, substrates of UGT1- isoenzymes, was not affected by adjuvant-induced arthritis. It seems, therefore, that adjuvant-induced arthritis in the rat leads to impaired glucuronidation of substrates of the UGT2B subfamily.
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PMID:Glucuronidation of R- and S-ketoprofen, acetaminophen, and diflunisal by liver microsomes of adjuvant-induced arthritic rats. 988 6

1. The main purpose was to develop a high-performance liquid chromatography (HPLC)-based method to assay serotonin glucuronidation activity using liver microsomal fractions. Application of this method was then demonstrated by determining serotonin UDP-glucuronosyltransferase (UGT) enzyme kinetics using human liver microsomes and recombinant human UGT1A6. Interspecies differences were also evaluated using liver microsomes from 10 different mammalian species. 2. Incubation of liver microsomes with serotonin, UDP-glucuronic acid and magnesium resulted in the formation of a single product peak using HPLC with fluorescence and ultraviolet absorbance detection. This peak was confirmed as serotonin glucuronide based on sensitivity to beta-glucuronidase and by obtaining the expected mass of 352 with positive-ion mass spectrometry. 3. Following a preparative HPLC isolation, the structure of this metabolite was established as serotonin-5-O-glucuronide by (1)H-NMR spectroscopy. 4. Enzyme kinetic studies showed apparent K(m) and V(max) of 8.8 +/- 0.3 mM and 43.4 +/- 0.4 nmoles min(-1) mg(-1) protein, respectively, for human liver microsomes, and 5.9 +/- 0.2 mM and 15.8 +/- 0.2 nmoles min(-1) mg(-1), respectively, for recombinant UGT1A6. 5. The order of serotonin-UGT activities in animal liver microsomes was rat > mouse > human > cow > pig > horse > dog > rabbit > monkey > ferret. Cat livers showed no serotonin-UGT activity. Heterozygous and homozygous mutant Gunn rat livers had 40 and 13%, respectively, of the activity of the normal Wistar rat, indicating a significant contribution by a rat UGT1A isoform to serotonin glucuronidation. 6. This assay provides a novel sensitive and specific technique for the measurement of serotonin-UGT activity in vitro.
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PMID:Serotonin (5-hydroxytryptamine) glucuronidation in vitro: assay development, human liver microsome activities and species differences. 1262 59

The purposes of this study were to develop a HPLC method to assay for haloperidol glucuronide (HALG); to apply this assay method to the in vitro determination of haloperidol (HAL) UDP-glucuronosyltransferase (UGT) enzyme kinetics in rat liver microsomes (RLM); and to identify the UGT isoforms catalyzing glucuronidation of HAL in rats. Incubation of Brij-activated RLM with HAL and UDP-glucuronic acid (UDPGA) in TRIS pH 7.4 buffer resulted in the formation of a single peak in the HPLC chromatogram at 270 nm. The identity of this peak was confirmed to be that of HALG by 1) beta-glucuronidase hydrolysis; 2) incubation without UDPGA; 3) UV spectral analysis; and 4) LC/MS/MS to yield the expected mass of 552.1. Enzyme kinetic studies using single enzyme Michaelis-Menton model showed an apparent Vmax = 271.9 +/- 10.1 pmoles min(-1) mg protein(-1) and Km = 61 +/- 7.2 microM. Glucuronidation activity in homozygous Gunn (j/j) rats was approximately 80% as compared to Sprague-Dawley RLM. HALG formation was approximately doubled in PB-induced RLM. There was no increase in glucuronidation activities in 3MC-induced RLM. The Gunn rat and the PB-induced RLM data suggest predominant but not exclusive involvement of the UGT2B family in the formation of HALG. Because the UGTs exhibit overlapping substrate specificities and most substrates are glucuronidated by more than one isoform, inhibition studies with UGT2B1 substrate probe testosterone and the UGT2B12 substrate probe borneol were conducted. UGT2B1 and UGT2B12 exhibited 40% and 90% inhibition of HAL glucuronidation, respectively. Thus, UGT2B12 and UGT 2B1 isoforms are responsible for catalyzing HAL glucuronidation in rats. Our HPLC assay provides a specific and sensitive technique for the measurement of in vitro HAL-UGT activity.
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PMID:Glucuronidation of haloperidol by rat liver microsomes: involvement of family 2 UDP-glucuronosyltransferases. 1501 Feb 63

The potential cancer therapeutic agent, 6,7-(dimethoxy-2, 4-dihydroindeno[1,2-c]pyrazol-3-yl)-(3-fluoro-phenyl)-amine (JNJ-10198409), formed three N-glucuronides that were positively identified by liquid chromatography-tandem mass spectrometry and NMR as N-amine-glucuronide (Glu-A), 1-N-pyrazole-glucuronide (Glu-B), and 2-N-pyrazole-glucuronide (Glu-C). All three N-glucuronides were detected in rat liver microsomes, whereas only Glu-A and -B were found in monkey and human liver microsomes. In contrast to common glucuronides, Glu-B was completely resistant to beta-glucuronidase. Kinetic analyses revealed that glucuronidation of JNJ-10198409 in human liver microsomes exhibited atypical kinetics that may be described by a two-site binding model. For the high affinity binding, K(m) values were 1.2 and 5.0 microM, and V(max) values were 2002 and 2,403 nmol min(-1) mg(-1) for Glu-A and Glu-B, respectively. Kinetic constants of low affinity binding were not determined due to low solubility of the drug. Among the human UDP-glucuronosyltransferases (UGTs) tested, UGT1A9, 1A8, 1A7, and 1A4 were the most active isozymes to produce Glu-A; for the formation of Glu-B, UGT1A9 was the most active enzyme, followed by UGT1A3, 1A7, and 1A4. Glucuronidation of JNJ-10198409 by those UGT1A enzymes followed classic Michaelis-Menten kinetics. In contrast, no glucuronides were formed by all UGT2B isozymes tested, including UGT2B4, 2B7, 2B15, and 2B17. Collectively, these results suggested that glucuronidation of JNJ-10198409 in human liver microsomes is catalyzed by multiple UGT1A enzymes. Since UGT1A enzymes are widely expressed in various tissues, it is anticipated that both hepatic and extrahepatic glucuronidation will likely contribute to the elimination of the drug in humans. Additionally, conjugation at the nitrogens of the pyrazole ring represents a new structural moiety for UGT1A-mediated reactions.
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PMID:N-glucuronidation of the platelet-derived growth factor receptor tyrosine kinase inhibitor 6,7-(dimethoxy-2,4-dihydroindeno[1,2-C]pyrazol-3-yl)-(3-fluoro-phenyl)-amine by human UDP-glucuronosyltransferases. 1645 2