Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P00492 (hypoxanthine-guanine phosphoribosyltransferase)
 2,385 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1,8-Dinitropyrene (1,8-DNP) was clearly mutagenic at the hprt locus in CHO cells, but not detectably mutagenic in V79 cells, following a 3-h treatment period. Preliminary data indicate that CHO, but not V79, cells have measurable levels of N-acetyltransferase activity, and this may contribute to the differential sensitivity of the two cell lines to the mutagenicity of 1,8-DNP.
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PMID:1,8-Dinitropyrene: comparative mutagenicity in Chinese hamster V79 and CHO cells. 238 80

In order to investigate the metabolic activation pathway of food-derived heterocyclic amines, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), cultured cell lines which stably expressed human cytochrome P4501A2 (CYP1A2) and N-acetyltransferases (NATs) were developed by the method of complementary DNA (cDNA) transfection. First, a cell line expressing CYP1A2, designated A2R-5, was established from the cell line CR-68, which was previously established by introducing NADPH-cytochrome P-450 reductase cDNA into Chinese hamster CHL cells. The expression of CYP1A2 in the transfected cells was confirmed by determining sensitivity to aflatoxin B1. As the next step, the A2R-5 as well as CR-68 cells were further transfected with human monomorphic NAT (NAT1) or polymorphic NAT (NAT2) cDNAs. The expression of NAT in the transfected cells was confirmed using p-aminobenzoic acid and sulfamethazine as substrates, while no activity was seen in parental CR-68 and A2R-5 cells. The cell line, ANP-25, which expressed both CYP1A2 and NAT2, was approximately 370- and 100-fold more sensitive to IQ and MeIQx, respectively, than parental CR-68 cells in cytotoxicity assays. There were no clear differences in sensitivity to both compounds among CR-68, A2R-5, and the cell lines which expressed NAT1 alone, NAT2 alone, and CYP1A2 plus NAT1. Mutagenicity of IQ and MeIQx at the hypoxanthine-guanine phosphoribosyltransferase locus was also detectable only in ANP-25 cells but not in A2R-5 or the cell line expressing CYP1A2 plus NAT1. From these results, it is proposed that both CYP1A2 and NAT2 (but not NAT1) are required for mutagenic activation of these compounds, implying that acetylator polymorphism may be an important risk factor in the carcinogenicity of these compounds.
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PMID:Stable expression of human CYP1A2 and N-acetyltransferases in Chinese hamster CHL cells: mutagenic activation of 2-amino-3-methylimidazo[4,5-f]quinoline and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline. 801 61

Genetically engineered cells transiently and stably expressing cytochrome P450 (P450), a key enzyme for biotransformation of a wide variety of compounds, have provided new tools for investigation of P450 functions such as P450-mediated metabolic activation of chemicals. This review will focus on the development of mammalian cell lines stably expressing P450s and application to toxicology testings. Stable expression systems have an advantage over transient ones in that a series of the process from metabolic activation of test compounds to the appearance of toxicological consequences occurs entirely in the same intact cells. Indeed, many cell lines stably expressing a single form of mammalian P450 have been established so far and applied to cytotoxic or genotoxic assays, the endpoints of which contained mutations at hprt and other gene loci, chromosomal aberrations, sister chromatid exchanges, micronuclei, morphological transformation, and 32P-postlabeling. Analyses of metabolites of toxic substances have also been carried out, using the intact cells or microsomal fractions prepared from the cells. The stable expression systems clearly indicate the form of P450 enzyme capable of activating a certain chemical. More recently, coexpression of P450 together with other components of microsomal electron transfer systems such as NADPH-cytochrome P450 reductase has been successfully performed to increase the metabolic capacity of the heterologously expressed P450. In addition, to reconstruct the entire metabolic activation system for certain heterocyclic amines, cell lines which simultaneously express a form of human P450 and a phase II enzyme, N-acetyltransferase, were established. These cells were highly sensitive to some carcinogenic heterocyclic amines. In genetic toxicology, such a coexpression system for two or more enzymes will provide useful materials which mimic in vivo activation systems.
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PMID:Genetically engineered cells stably expressing cytochrome P450 and their application to mutagen assays. 967 35

2-Amino-3-methyl-9H-pyrido[2,3-b]indole (MeAalphaC) and some metabolites were investigated for mutagenicity in mammalian cell lines and bacterial strains engineered for the expression of human enzymes. MeAalphaC induced gene mutations (studied at the hprt locus) in Chinese hamster V79-derived cells co-expressing cytochrome (CYP) 1A2 and sulphotransferase (SULT) 1A1 even at a concentration of 30 nM, but was inactive in cells co-expressing CYP1A2 and N-acetyltransferase (NAT) 1 or 2. MeAalphaC, tested in the presence of rat liver post-mitochondrial fraction, showed strongly enhanced mutagenicity in a Salmonella typhimurium strain expressing human SULT1A1 compared with the control (recipient) strain TA1538/1,8-DNP (deficient in endogenous acetyltransferase). Mutagenicity was also enhanced, although to a lesser extent, when NAT2 was expressed in the latter strain. The metabolite, 2-hydroxylamino-3-methyl-9H-pyrido[2,3-b]indole (N-OH-MeAalphaC) was a direct mutagen to strains TA1538 and TA1538/ 1,8-DNP. This mutagenicity was strongly enhanced in corresponding strains expressing SULT1A1. A moderate enhancement was observed when SULT1A2, SULT1B1, SULT1C2 or NAT2 were expressed in strain TA1538. The remaining enzymes studied (SULT1A3, 1C1, 1E1, 2A1, 2B1a, 2B1b, 4A1 and NAT1) did not indicate any activation of N-OH-MeAalphaC. Preliminary mutagenicity experiments in SULT-expressing S.typhimurium strains were conducted with other hydroxylated metabolites of MeAalphaC. The phenols, 6- and 7-hydroxy-MeAalphaC, were inactive under the conditions studied. The benzylic alcohol, 2-amino-3-hydroxymethyl-9H-pyrido[2,3-b]indole, was mutagenic in a strain expressing SULT1A1, but its activity was much weaker than that of N-OH-MeAalphaC. Thus, N-hydroxylation (e.g. mediated by CYP1A2) and sulpho conjugation (primarily mediated by SULT1A1) was the dominating activation pathway of MeAalphaC in model systems engineered for human enzymes. Some other SULT forms as well as NAT2 were also capable of activating N-OH-MeAalphaC, although with much lower efficiency than SULT1A1. Another minor activation pathway involved benzylic hydroxylation followed by sulpho conjugation by SULT1A1.
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PMID:Bioactivation of the heterocyclic aromatic amine 2-amino-3-methyl-9H-pyrido [2,3-b]indole (MeAalphaC) in recombinant test systems expressing human xenobiotic-metabolizing enzymes. 1472 82