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)

A thermospray liquid chromatographic/mass spectrometric method has been developed for direct determination of cotinine-N-glucuronide in the urine of smokers. Quantification was performed using methyl-d3-cotinine-N-glucuronide as internal standard and monitoring the protonated aglycons. Using a simple preparation, urine samples from four smokers were analyzed and the results compared favorably with those from a previously reported method that quantifies aglycon release following beta-glucuronidase treatment. Amounts of cotinine-N-glucuronide found in urine from smokers ranged from less than 0.7 to 21 nmol ml-1, indicating wide inter-individual variability in the metabolic production of this metabolite. Cotinine-N-glucuronide was found to be the second most abundant urinary nicotine metabolite. A similar method was developed for trans-3'-hydroxycotinine-N-glucuronide but this compound was not detected in smokers' urine.
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PMID:Direct determination of cotinine-N-glucuronide in urine using thermospray liquid chromatography/mass spectrometry. 812 88

The 1,3-diethyl-2-thiobarbituric acid (DETBA) assay for nicotine metabolites has been improved so that it can be used to determine the concentrations of nicotine and up to 12 metabolites in the urine of humans and laboratory animals, including phase 2 metabolites. The products of beta-glucuronidase cleavage found in human urine were mainly trans-3'-hydroxycotinine, cotinine, and a small amount of nicotine. Following isolation, spectroscopic analyses showed the structure of the nicotine DETBA derivative to be the one-to-one ring-opening product of DEBTA and the cyanopyridinium salt of nicotine.
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PMID:High-performance liquid chromatographic determination of nicotine and its urinary metabolites via their 1,3-diethyl-2-thiobarbituric acid derivatives. 845 8

trans-3'-Hydroxycotinine (THOC) has been recognized as the most abundant metabolite of nicotine. In an attempt to assess THOC and cotinine (COT) concentrations during nicotine transdermal therapy, we developed a new quantitative gas chromatography-mass spectrometry (GC-MS) method for simultaneous determination of total and free THOC and COT in human urine. The method utilizes the following: (a) hydrolysis of conjugated THOC and COT by beta-glucuronidase; (b) basic extraction of THOC and COT with mixed dichloromethane and n-butyl acetate; (c) derivatization of THOC with bis(trimethylflurosilyl)acetamide; and (d) separation and identification by GC-MS with selective ion monitoring. Lower limits of quantification for the assay were 50 and 20 microg/L for THOC and COT, respectively. The intra- and interassay CVs were 4.4% and 11% for THOC, and 3.9% and 10% for COT at 1000 microg/L. The results from six consecutive 24-h urine collections in 71 subjects administered daily transdermal nicotine doses of 11, 22, and 44 mg showed that, on average, free THOC was 76% of total THOC and free COT was 48% of total COT in all subjects. THOC is the major metabolite of nicotine and constitutes 20% of total nicotine intake at steady state, whereas urinary nicotine and COT excretion were 8% and 17%, respectively. The method is useful for simultaneous determination of free and total THOCand COT and can be used to assess the urinary excretion of these metabolites during transdermal nicotine therapy.
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PMID:A new gas chromatography-mass spectrometry method for simultaneous determination of total and free trans-3'-hydroxycotinine and cotinine in the urine of subjects receiving transdermal nicotine. 989 42

Recently, the detection of urinary glucuronide conjugates of nicotine and its two major metabolites, trans-3'-hydroxycotinine and cotinine, showed that glucuronidation is an important pathway of nicotine metabolism in humans. (S)-(-)-Nicotine-N(+)-1-beta-glucuronide (quaternary N-glucuronide with linkage through the pyridino-nitrogen of nicotine) was shown to be an important nicotine metabolite of humans in vivo. The present study was undertaken to develop an animal model for this process, in order to ascertain the factors influencing quaternary N-glucuronide formation. (S)-(-)-Nicotine-N(+)-1-beta-glucuronide was formed in vitro when [2'-14C]-nicotine was incubated with Triton X-100 activated marmoset hepatic microsomes in the presence of uridine diphosphoglucuronic acid; it was not formed when activated microsomal preparations of rabbit, guinea-pig, or rat were used as enzyme source. The glucuronide was characterised by comparison with authentic synthetic (S)-(-)-nicotine-N(+)-1-beta-glucuronide using HPLC. The rate of formation of the glucuronide was almost linear during up to four hours of incubation, but still only accounted for a maximum of 6.0% of the available substrate at the end of five hours incubation. The synthetic and biosynthetic (S)-(-)-nicotine-N(+)-1-beta-glucuronides were hydrolysed by beta-glucuronidase and alkali, but were resistant to acid hydrolysis. The results support the concept that the marmoset may be a good animal species to mimic man in studies of nicotine metabolism during exposure to tobacco smoke. In vitro studies using (+/-)-trans-3'-hydroxycotinine or (S)-(-)-cotinine (as potential substrate) and [14C]-uridine diphospho-glucuronic acid (as cofactor) failed to produce any new radiolabelled glucuronide when the above microsomal preparations were used.
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PMID:Evidence for the biosynthesis of A glucuronide conjugate of (S)-(-)-nicotine, but not (S)-(-)-cotinine or (+/-)-trans-3'-hydroxycotinine by marmoset hepatic microsomes. 1071 38

An SPE-LC-MS/MS method was developed, validated and applied to the determination of nicotine and five major metabolites in human urine: cotinine, trans-3'-hydroxycotinine, nicotine-N-glucuronide, cotinine-N-glucuronide and trans-3'-hydroxycotinine-O-glucuronide. A 500 microL urine sample was pH-adjusted with phosphate buffer (1.5 mL) containing nicotine-methyl-d3, cotinine-methyl-d3 and trans-3'-hydroxycotinine-methyl-d3 internal standards. For the unconjugated metabolites, an aliquot (800 microL) of the buffered solution was applied to a 30 mg Oasis HLB-SPE column, rinsed with 2% NH4OH/H2O (3.0 mL) and H2O (3.0 mL) and eluted with methanol (500 microL). The eluate was analyzed isocratically (100% methanol) by LC-MS/MS on a diol column (50 x 2.1 mm). For the total metabolites, a beta-glucuronidase/buffer preparation (100 microL) was added to the remaining buffered solution and incubated at 37 degrees C (20 h). An aliquot (800 microL) of the enzymatically treated buffered solution was extracted and analyzed in the same manner. The conjugated metabolites were determined indirectly by subtraction. The quantitation range of the method (ng/mL) was 14-10,320 for nicotine, 15-9800 for cotinine and 32-19,220 for trans-3'-hydroxycotinine. The validated method was used to observe diurnal variations from a smoker's spot urine samples, elimination half-lives from a smoker's 24 h urine samples and metabolite distribution profiles in the spot and 24 h urine samples.
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PMID:Validation and application of a method for the determination of nicotine and five major metabolites in smokers' urine by solid-phase extraction and liquid chromatography-tandem mass spectrometry. 1565 Oct 85