Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.1.1.67 (thiopurine methyltransferase)
 551 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Involvement of the bacterial thiopurine methyltransferase (bTPMT) in natural selenium methylation by freshwater was investigated. A freshwater environment that had no known selenium contamination but exhibited reproducible emission of dimethyl selenide (DMSe) or dimethyl diselenide (DMDSe) when it was supplemented with an organic form of selenium [(methyl)selenocysteine] or an inorganic form of selenium (sodium selenite) was used. The distribution of the bTPMT gene (tpm) in the microflora was studied. Freshwater bacteria growing on 10 micro M sodium selenite and 10 micro M sodium selenate were isolated, and 4.5 and 10% of the strains, respectively, were shown by colony blot hybridization to hybridize with a Pseudomonas syringae tpm DNA probe. Ribotyping showed that these strains are closely related. The complete rrs sequence of one of the strains, designated Hsa.28, was obtained and analyzed. Its closest phyletic neighbor was found to be the Pseudomonas anguilliseptica rrs sequence. The Hsa.28 strain grown with sodium selenite or (methyl)selenocysteine produced significant amounts of DMSe and DMDSe. The Hsa.28 tpm gene was isolated by genomic DNA library screening and sequencing. BLASTP comparisons of the deduced Hsa.28 bTPMT sequence with P. syringae, Pseudomonas aeruginosa, Vibrio cholerae, rat, and human thiopurine methyltransferase sequences revealed that the levels of similarity were 52 to 71%. PCR-generated Escherichia coli subclones containing the Hsa.28 tpm open reading frame were constructed. E. coli cells harboring the constructs and grown with sodium selenite or (methyl)selenocysteine produced significant levels of DMSe and DMDSe, confirming that the gene plays a role in selenium methylation. The effect of strain Hsa.28 population levels on freshwater DMSe and DMDSe emission was investigated. An increase in the size of the Hsa.28 population was found to enhance significantly the emission of methyl selenides by freshwater samples supplemented with sodium selenite or (methyl)selenocysteine. These data suggest that bTPMT can play a role in natural freshwater selenium methylation processes.
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PMID:Freshwater bacteria can methylate selenium through the thiopurine methyltransferase pathway. 1283 45

Dimethyl selenide (DMSe) and dimethyl diselenide (DMDSe) emissions by soil samples spiked with selenite or (methyl)selenocysteine, with or without a supplement of nutrient broth and glucose were measured. DMSe was the main form of volatile Se produced, and was observed for both Se-substrates. DMDSe was only emitted from soils spiked with (methyl)selenocysteine. Two bacterial thiopurine methyltransferases (TPMTs), TPMT-I and TPMT-E, have been reported to be involved in DMSe and DMDSe emissions [J. Bacteriol. 184 (2002) 3146; Appl. Environ. Microbiol. 69 (2003) 3784]. To establish if these TPMTs or other members of their gene family could have contributed to the DMSe emissions observed, the diversity of bTPMT gene (tpm) sequences among the soils of this study was investigated. Total DNAs from these soils were extracted and screened using the tpm PTCF2-PTCR2 consensus primers defined to PCR amplify this gene family. The PCR products obtained from two soils were cloned, analysed by PCR-RFLP, and sequenced. Their analysis showed an important diversity of tpm lineages (around 12) in soils. Phylogenetic analysis of the deduced TPMT sequences of these soils revealed lineages not previously recorded in the databases, sequences closely related or identical to freshwater TPMTs, or sequences encoding TPMTs closely related to those of Pseudomonas fragi TPMT-K, Pseudomonas Hsa.28 TPMT-I, or Colwellia psychrerythraea TPMT-Z. Nested PCRs, allowing detection of about 13 distinct tpm soil and freshwater lineages by PTCF2-PTCR2 PCR screenings, were performed on the soil total DNAs. These PCRs confirmed the sequencing data, and allowed to recover lineages not detected by the cloning strategy. These results indicate that soils, like the freshwater samples, harbour TPMT-I gene sequences but may also have distinct tpm lineages. This study further supports our hypothesis that TPMTs contribute to DMSe soil emissions.
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PMID:Distribution and genetic diversity of bacterial thiopurine methyltransferases in soils emitting dimethyl selenide. 1700 90