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

Since drug-metabolizing enzymes may influence the toxic response of tissues or organs to drugs, we studied their expression in human and colon tumor tissues, in an attempt to find new targets for chemotherapy and also to explain the intrinsic drug-insensitivity of most colon tumors to anticancer drugs. In the present work, we compared human colorectal tumors and peritumoral tissues to a mouse colorectal tumor (Co38) and normal murine colon with regard to their main drug-metabolizing enzyme systems. We investigated cytochromes P-450 (1A1/1A2, 2B1/B2, 2C, 2E1, 3A) and epoxide hydrolase (EH) by immunoblotting. Total glutathione (GSH) and the activities of the following enzymes: total GST, selenium-independent glutathione peroxidase (GPX), 1,2-dichloro-4-nitrobenzene-GST (DCNB-GST), ethacrynic acid-GST (EA-GST), UDP-glucuronosyltransferase 1 (UDPGT), beta-glucuronidase (beta G), sulfotransferase (ST) and sulfatase (S) were investigated by fluorometric and spectrophotometric assays. Results obtained by immunoblotting showed that mouse colon tumor Co38 did not express any of the probed cytochromes P-450, whereas human tumors showed the presence of cytochrome P-450 3A. EH was not expressed in either mouse colon tumor Co38 or normal mouse colon, whereas it was expressed in human peritumoral and tumoral colon tissues at similar levels. GPX and EA-GST were detected in all tumoral and non tumoral tissues of both species. DCNB-GST was expressed in all murine tissues investigated, but was not found in human tissues. For human peritumoral and tumoral colorectal tissues there was no significant difference between GST isoenzymes levels, whereas mouse colon tumor Co38 had a lower expression of DCNB-GST and EA-GST compared to normal mouse colon. No significant difference was observed between human tumors and peritumoral tissues for total GST, UDPGT1, beta G, ST and S activities. For murine colon tissues, the conjugation pathways (total GST, UDPGT1 and ST) were lower in Co38, whereas the opposite was observed for the hydrolytic enzymes (beta G and S). In conclusion, despite similarities between human and murine colon tumors, mouse colon tumor Co38 appears different from human colon tumors for many drug-metabolizing enzyme systems. These interspecies differences may have implications with regard to drug screening methodologies and preclinical evaluation of candidate anticancer drugs useful in the chemotherapy of human colorectal tumors.
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PMID:[Screening of principal enzymes involved in the metabolism of anticancer drugs in human and murine colonic tumors]. 817 93

To better understand the importance of drug-metabolizing enzymes in carcinogenesis and anticancer drug sensitivity of human non-small cell lung cancer, we studied the main drug-metabolizing enzyme systems in both lung tumors and their corresponding nontumoral lung tissues in 12 patients. The following enzymes were assayed by Western blot analysis: cytochromes P-450 (1A1/A2, 2B1/B2, 2C8-10, 2E1, 3A4); epoxide hydrolase; and glutathione S-transferase isoenzymes (GST-alpha, -mu, and -pi). The activity of the following enzymes or cofactor were determined by spectrophotometric or fluorometric assays: glutathione S-transferase (GST); total glutathione; UDP-glucuronosyltransferase; beta-glucuronidase; sulfotransferase; and sulfatase. Results showed the presence of cytochrome P-450 1A1/1A2 in both tumoral and nontumoral tissues. P-450 1A1/1A2 levels were 3-fold lower in tumors compared to corresponding nontumoral tissues (P < 0.05). None of the other probed cytochromes P-450 were detected in either tumoral or nontumoral lung tissues. For the glutathione system, no significant difference between tumoral and nontumoral tissues was observed (GST activity, glutathione content, GST-alpha, -mu, and -pi). A positive linear correlation was observed between GST activity and GST-alpha or GST-pi. No significant difference was observed for the glucuronide and the sulfate pathways and their corresponding hydrolytic enzymes. Epoxide hydrolase was significantly decreased in tumors compared to nontumoral lung tissues (P < 0.05). In conclusion, these results showed differences between non-small cell lung tumors and nontumoral tissues for cytochrome P-450 1A1/1A2 and epoxide hydrolase. These differences between tumors and peritumoral tissues with regard to these drug-metabolizing enzymes could reflect differences occurring after malignant transformation and may play a role in drug sensitivity to anticancer drugs.
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PMID:Main drug- and carcinogen-metabolizing enzyme systems in human non-small cell lung cancer and peritumoral tissues. 840 35

Non-Hodgkin's lymphomas (NHL) are one of the most chemosensitive human malignancies. Complete response (CR) is often achieved, but many patients relapse and a second CR is difficult to obtain because of the development of chemoresistance. In an attempt to better understand the biology and the chemosensitivity of these lymphoid tumors, we assessed the main drug-metabolizing enzyme systems in normal lymphocytes, chemosensitive NHL and chemoresistant NHL. Cytochromes P-450 (1A1/A2, 2B1/B2, 2C8-10, 2E1, 3A4), epoxide hydrolase and glutathione S-transferases (GST-alpha, -mu, -pi) were assayed by immunoblotting. UDP-glucuronosyltransferase, beta-glucuronidase, sulfotransferase, sulfatase, GST activity, and glutathione (GSH) content, were determined by spectral assays. Results showed the absence of all probed cytochromes P-450 in normal lymphocytes and NHL cells tested. GST activity was significantly lower in chemoresistant NHL compared to normal lymphocytes. GST-alpha was not detected in either normal lymphocytes or NHL cells. GST-pi was the predominant isoenzyme, and GST-mu was not detected in chemosensitive NHL. GSH content was significantly lower in chemoresistant NHL compared to other lymphoid tissues tested. The conjugating enzymes UDP-glucuronosyltransferase and sulfatase were similar in either chemoresistant NHL compared to chemosensitive NHL. The activity of the hydrolytic enzyme beta-glucuronidase was lower in chemoresistant compared to chemosensitive NHL, whereas sulfatase was higher in sensitive NHL compared to normal lymphocytes. Epoxide hydrolase was not detected in either normal or NHL cells tested. In conclusion, these studies did not show any cytochrome P-450 in human lymphoid cells tested, but pointed out noteworthy differences for other enzyme systems tested.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Main drug-metabolizing enzyme systems in human non-Hodgkin's lymphomas sensitive or resistant to chemotherapy. 853 97

To understand the factors involved in the enhanced testicular toxicity of di(2-ethylhexyl)phthalate (DEHP) in developing animals, po doses of 50, 100, 250 or 500 mg DEHP/kg were administered to 25-d-old albino rats for 30 consecutive days. Activities of testicular and hepatic cytochrome P-450 enzymes were determined. A dose-dependent increase in the activities of lactate dehydrogenase and gamma-glutamyl transpeptidase and a decrease in sorbitol dehydrogenase was observed in the testes. The activity of beta-glucuronidase increased at dosages of 250 and 500 mg/kg, while acid phosphatase decreased. Testes had marked destructive changes in the advanced germ cell layers at dosages of 250 and 500 mg/kg, which supports biochemical studies indicating that DEHP interacts with the maturation process of the testes. The dose-dependent decrease in hepatic cytochrome P-450 levels and the activities of ethylmorphine N-demethylase and aniline hydroxylase suggest that impaired metabolism of DEHP could lead to higher amounts of the diester or its metabolites reaching the testes; this may result in enhanced vulnerability of the testes to DEHP in developing animals.
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PMID:Testicular toxicity of Di(2-ethylhexyl)phthalate in developing rats. 854 Feb 15

Tacrolimus is extensively metabolized by the cytochrome P-450 system. Hepatic metabolic phase I reactions of tacrolimus include mainly demethylation and/or hydroxylation. No valid data have been published on phase II pathways (glucuronide- or sulfo-conjugation). In order to investigate these pathways, different beta-glucuronidase/sulfatase enzyme preparations were used to hydrolyse the conjugates potentially present in human bile extracts. Two analytical methods were used: a non-specific method, MEIA, and a specific combined HPLC/MEIA method. The influence of the extraction pH was investigated. After beta-glucuronidase hydrolysis and extraction at pH 5, tacrolimus concentrations, obtained either from HPLC-MEIA or MEIA, always appeared significantly higher, suggesting the presence of glucuronides in the bile. When the extraction was performed at pH 1.5, only the HPLC-MEIA concentrations appeared higher after hydrolysis. MEIA concentrations obtained before and after hydrolysis were similar. These data are consistent with the fact that glucuronides are extracted at pH 1.5 but not at pH 5 and suggest first that, without hydrolysis, the extracted glucuronides are separated from the tacrolimus fraction in the HPLC-MEIA procedure, and second, that the glucuronides are cross-detected by the monoclonal antibody in the immunoassay. From these data, it is concluded that clues have been found, suggesting the presence in human bile of tacrolimus glucuronides, which cross-react with the monoclonal antibody, provided they are extracted in the sample tested.
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PMID:Excretion of tacrolimus glucuronides in human bile. 935 2

The objective of this study was to determine the metabolic fate and disposition of the antitumor camptothecine derivative irinotecan (CPT-11). Ten patients with histological proof of malignant solid tumor received 200 mg/m2 CPT-11 as a 90-min i.v. infusion, followed by a 1.5-h i.v. infusion of cisplatin (60 or 80 mg/m2). Plasma, urine, and feces were collected for 56 h and analyzed by a specific reversed-phase high-performance liquid chromatographic assay for the parent drug and all four metabolites positively identified to date: SN-38; its beta-glucuronide conjugate, SN-38 beta-glucoronide (SN-38G); 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]-carbonyloxycamptothecine (APC); and 7-ethyl-10-[4-N-(1-piperidino)-1-amino]-carbonyloxycamptothecine (NPC). A three-exponential decline was observed in plasma for all compounds, with a clear predominance of the parent drug [25.6+/-5.71 microM x h (CPT-11) versus 15.8+/-3.51 microM x h (total metabolites)]. Total urinary excretion was 28.1+/-10.6% of the dose, with unchanged CPT-11 and SN-38G as the main excretion products. Whereas renal clearance of SN-38 was only a minor route of drug elimination, fecal concentrations of this compound were unexpectedly high (on average, 2.45% of the dose), suggestive of intestinal hydrolysis of SN-38G by bacterial beta-glucuronidase. CPT-11 and the other metabolites could also be identified from fecal extracts, with a very minor contribution overall of the cytochrome P-450-mediated compounds 7-ethyl-10-[4-N-(1-piperidino)-1-amino]-carbonyloxycamptothecine and 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]-carbonyloxycamptothecine. Surprisingly, fecal excretion accounted for only 24.4+/-13.3% of the dose, leading to a total excretion of approximately 52%. These data indicate that half of the dose in urine and feces may constitute some further unknown nonextractable or nonfluorescent metabolites. The findings from this study should be of importance as a guide to further therapeutic evaluation of this drug.
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PMID:Irinotecan (CPT-11) metabolism and disposition in cancer patients. 982 38

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

One of the early genes in aflatoxin biosynthesis, avnA, encodes a pathway-specific cytochrome P-450 monooxygenase that catalyzes the hydroxylation of the polyketide anthraquinone, averantin. Based on beta-glucuronidase (GUS) reporter and electrophoretic mobility shift assays, promoter sites upstream of -118 bp in the 367-bp verB-avnA intergenic region are not required for avnA gene activity. Therefore, only the -100 to -110 site of the four putative binding sites for AFLR, the aflatoxin biosynthetic pathway transcription regulatory protein (consensus binding sequence: 5'-TCGN(5)CGR-3') was required for elevated avnA expression.
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PMID:Promoter elements involved in the expression of the Aspergillus parasiticus aflatoxin biosynthesis pathway gene avnA. 1076 May 64

The active metabolite of irinotecan (CPT-11), 7-ethyl-10-hydroxycamptothecin (SN-38), is either formed through enzymatic cleavage of CPT-11 by carboxyl esterases (CEs) or through cytochrome P-450 3A-mediated oxidation to 7-ethyl-10-[4-(1-piperidino)-1-amino] carbonyloxycamptothecin (NPC) and a subsequent conversion by CE. In the liver, SN-38 is glucuronidated (SN-38G) by UGT1A1, which also conjugates bilirubin. Fourteen patients were treated with 350 mg/m2 CPT-11, and we performed pharmacokinetic analysis during a 500-h collection period. The half-life and area under the plasma concentration-time curve of SN-38 were 47+/-7.9 h and 2.0+/-0.79 microM x h, respectively, both representing a 2-fold increase as compared with earlier reported estimates (A. Sparreboom et al, Clin. Cancer Res., 4: 2747-2754, 1998). As an explanation for this phenomenon, we noted substantial formation of SN-38 from CPT-11 and NPC by plasma CE, consistent with the low circulating levels of NPC observed. In addition, transport studies in Caco-2 monolayers indicated that nonglucuronidated SN-38 could cross the membrane from apical to basolateral, indicating the potential for recirculation processes that can prolong circulation times. Interestingly, individual levels of fecal beta-glucuronidase, which is known to mediate SN-38G hydrolysis, were not related to any of the SN-38 kinetic parameters (r = 0.09; P = 0.26), suggesting that interindividual variation in this enzyme is unimportant in explaining SN-38 pharmacokinetic variability. We have also found, in contrast to earlier data, that SN-38G/SN-38 plasma concentration ratios decrease over time from approximately 7 (up to 50 h) to approximately 1 (at 500 h). This decrease could be explained by the fact that glucuronidation of SN-38 and bilirubin is increasingly competitive at lower drug levels. In addition, no evidence was found for SN-38G transport through the Caco-2 cells. Our findings indicate that until now the circulation time of SN-38 has been underestimated. This is of crucial importance to our understanding of the clinical action of CPT-11 and for future pharmacokinetic/pharmacodynamic relationships.
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PMID:Factors involved in prolongation of the terminal disposition phase of SN-38: clinical and experimental studies. 1099 19

Sevoflurane has been used in the last few years in brief surgical operations, either alone or in combination with nitrous oxide. Occupationally exposed groups include anesthesiologists, surgeons and operating room nurses. In 1977 the National Institute for Occupational Safety and Health (NIOSH) recommended that occupational exposure to halogenated anesthetic agents (halothane, enflurane, and isoflurane), when used as the sole anesthetic, should be controlled so that no worker would be exposed to time-weighted average concentrations greater than 2 ppm during anesthetic administration. When halogenated anesthetics are associated with nitrous oxide, NIOSH recommends that the limit value should not exceed 0.5 ppm. We think these recommendations can be extended to sevoflurane. Metabolism of sevoflurane is catalyzed by cytochrome P-450; this involves oxidation of the fluoromethyl side chain of the molecule, followed by glucuronidation. Two urinary metabolites of sevoflurane have been identified: inorganic fluoride (which, however, is not specific) and a non-volatile compound that yields hexafluoroisopropanol (HFIP) when digested with the enzyme beta-glucuronidase. In order to investigate the role of urinary HFIP as an indicator of occupational exposure to sevoflurane (CI, ppm), CI was measured in 145 members of 18 operating room staffs. The measurements of the time-weighted average of CI in the breathing zone were made by means of diffusive personal samplers. Each sampler was exposed during the whole working period. Sevoflurane was desorbed with CS2 from charcoal and the concentrations were measured on a gas chromatograph (GC) equipped with a mass selective detector (MSD). The GC was equipped with a 25 meter cross-linked phenylmethylsilicon column (internal diameter 0.2 mm). GC conditions were as follows: injector column temperature = 200 degrees C; column temperature = 30 degrees C; carrier gas = helium; injection technique of samples = splitless. The analytical conditions for the MSD were the following: ion mass monitored = 131 m/e; dwell time = 50 msec; selected ion monitoring window time = 0.1 amu; electromultiplier = 400 V. Urine samples were collected near the end of the shift and were analyzed for HFIP by head-space gas chromatography after glucuronide hydrolysis. 0.5 ml of urine and 1.5 ml of 10 M sulfuric acid were added to 21.8 ml headspace vials. The vials were immediately capped, vortexed, and loaded into the headspace autosampler. Samples were maintained at 100 degrees C for 30 min, after which glucuronide hydrolysis was 99% complete. Analyses were performed on a GC equipped with a MSD. The analytical conditions for urine analysis were as follows: cross-linked 5% phenylmethylsilicon column (internal diameter 0.2 mm, length 25 m); column temperature = 35 degrees C; carrier gas = helium. The analytical conditions for the MSD were: monitored ions = 51.05 and 99; dwell time = 100 ms; selected ion monitoring window time = 0.1 amu; electromultiplier voltage = 2000 Volt. With our analytical procedure, the detection limit of HFIP in urine was 20 micrograms/L. The variation coefficient (CV) for HFIP measurement in urine was 8.7% (on 10 determinations; mean value = 1000 micrograms/L). The median value of CI was 0.77 ppm (Geometric Standard Deviation = 4.08; range = 0.05-27.9 ppm). The correlation between CI and HFIP (Cu, microgram/L) was: Log Cu (microgram/L) = 0.813 x Log CI (ppm) + 2.517 (r = 0.79, n = 145, p < 0.0001). On the basis of the equation it was possible to establish tentatively the biological limit values corresponding to the respective occupational exposure limit values proposed for sevoflurane. According to our experimental results, HFIP values of 488 micrograms/L and 160 micrograms/L correspond to airborne sevoflurane concentrations of 2 and 0.5 ppm respectively.
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PMID:[Biological monitoring of occupational exposure to sevoflurane]. 1151 50


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