Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.4.2.8 (hypoxanthine-guanine phosphoribosyltransferase)
 2,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

5-(Hydroxymethyl)furfural (HMF), one of the major intermediate products in the Maillard reaction, is present in a wide variety of foods. This aldehyde is formed as a decomposition product of glucose and fructose in foodstuffs subject to cooking or heat sterilization. It has been found to possess mutagenic and DNA strand-breaking activity. However, the mechanisms by which HMF exerts its genotoxicity remain unclear. The present study was undertaken to determine if HMF could be metabolically activated via esterification of the allylic hydroxyl group. In support of this concept, the chemically synthesized sulfuric acid ester,5-[(sulfooxy)-methyl]furfural (SMF), exhibited direct mutagenicity at both thymidine kinase and hypoxanthine-guanine phosphoribosyltransferase loci in human lymphoblasts. This reactive ester also induced 8-azaguanine-resistant mutants in Salmonella typhimurium TM677 in a dose-dependent manner. The intrinsic mutagenicity of SMF was enhanced by addition of extra chloride ion to the assay medium. The model allylic derivative, 5-(chloromethyl)furfural, was also mutagenic and cytotoxic in bacteria, but much more active than the sulfuric acid ester in this regard. In contrast to (sulfooxy)methyl and chloromethyl derivatives of HMF,2-[(sulfooxy)-methyl]- and 2-(chloromethyl)furans which lack the aldehyde functionality did not exhibit significant mutagenicity. Rodent hepatic cytosols contained sulfotransferase activity responsible for the formation of the reactive allylic sulfuric acid ester metabolite from HMF.
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PMID:Activation of the Maillard reaction product 5-(hydroxymethyl)furfural to strong mutagens via allylic sulfonation and chlorination. 807 62

6-Sulfooxymethylbenzo[a]pyrene (SMBP) is an ultimate and reactive form of 6-hydroxymethybenzo[a]pyrene (HMBP), which is converted into SMBP by the mediation of sulfotransferase. SMBP and HMBP with metabolic activation were mutagenic to S. typhimurium TA98 and TA100. The number of mutation per plate in strain TA98 was proportional to the concentrations of SMBP ranging from 0.2 to 1.0 nmol/plate, whereas that in strain TA100 was decreased at concentrations above 0.6 nmol/plate. The mutation frequencies by HMBP was also increased in a dose dependent manner in both strains. Furthermore, SMBP and HMBP were highly mutagenic and cytotoxic to Chinese hamster lung fibroblast (V79) cells. A dose-dependent increase in mutation frequencies at both hypoxanthine:guanine phosphoribosyltransferase (HGPRT) and sodium/potassium-ATPase (Na/K-ATPase) loci were found in V79 cells treated with SMBP and HMBP. The cytotoxicity of SMBP was increased with the increasing concentrations up to 2.5 microM, where the survival frequency and growth rate were decreased to almost 40% and 30% of the control value, respectively. The survival frequencies of V79 cells by HMBP were also decreased in a dose dependent manner up to 180 microM as similar to those of SMBP but the effects were less remarkable. SMBP was progressively accumulated in V79 cells, reaching plateau in just 30 min. A dose dependent increase in complex formation with DNA or proteins was observed by treatment with SMBP. The mutagenicity and cytotoxicity of SMBP and HMBP may be derived from their binding capacity to DNA in V79 cells and S. typhimurium.
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PMID:Mutagenicity of 6-sulfooxymethylbenzo[a]pyrene in Salmonella typhimurium and Chinese hamster V79 cells. 954 51

Metabolic activation of 17beta-estradiol (E2) to catechols and quinones together with lack of deactivation constitute risk factors in human breast carcinogenesis. E2-catchols are generated by cytochrome P450-dependent monooxygenases (CYPs). Deactivation of E2, E2-catechols, and E2-quinones is mediated by UDP-glucuronosyltransferase (UGT), sulfotransferase (SULT), catechol-O-methyltransferase (COMT), glutathione-S-transferase (GST), and NADPH-quinone-oxidoreductase (QR) isozymes, respectively. The aim of the present study was to quantify mRNA levels of E2-metabolizing isozymes expressed in MCF-7 cells cultured in the presence/absence of steroids by reverse transcription/competitive PCR in relation to the housekeeping gene hypoxanthine-guanine phosphoribosyltransferase and compare them with expression levels in normal human mammary gland (MG) and liver tissue. CYP1A1, 1B1, SULT1A1, 1A2, membrane-bound and soluble COMT, GSTT1, QR1, and UGT2B7 were detected in both tissues and MCF-7 cells; however, most enzymes were expressed at least tenfold higher in liver. Yet, CYP1B1 was expressed as high in breast as in liver and UGTs were not detected in MCF-7 cells cultured with steroids. MCF-7 cells cultured steroid-free additionally expressed CYP1A2 as well as UGT1A4, 1A8, and 1A9. Normal human liver but not MG expressed CYP1A2, 3A4, UGT1A1, 1A3, 1A4, 1A9, and SULT2A1. UGT1A8 was only detected in MCF7 cells but was not found in human liver. Thus, our study provides a comprehensive overview of expression levels of E2-metabolizing enzymes in a popular in vitro model and in human tissues, which will contribute to the interpretation of in vitro studies concerning the activation/deactivation of E2.
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PMID:Gene expression of 17beta-estradiol-metabolizing isozymes: comparison of normal human mammary gland to normal human liver and to cultured human breast adenocarcinoma cells. 1849 89