Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026918 (Mycobacterium)
 52,428 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In Mycobacterium leprae, thioredoxin and thioredoxin reductase are expressed from a single gene. This results in the expression of a hybrid protein with subunits attached to each other by a hydrophilic peptide linker. In all other organisms studied so far, thioredoxin (Trx) and thioredoxin reductase (TR) are expressed as two separate proteins. This raises the question of whether the hybrid protein is enzymatically active and, if so, whether TR reduces its own Trx partner or alternatively a heterologous Trx subunit. To address this question, the hybrid TR/Trx protein of M. leprae as well as the individual parts of the hybrid gene coding for either TR or Trx were overexpressed in Escherichia coli and purified. The purified proteins were tested for their ability to catalyze NADPH-dependent insulin disulfide reduction. Here we show that the M. leprae hybrid protein is indeed enzymatically active. Compared with the enzymatic activity of the separately expressed Trx and TR proteins, the hybrid protein is shown to be more efficient, particularly at low equimolar concentrations. This suggests that the hybrid protein of M. leprae is active by itself and that its activity involves intramolecular interactions between the TR and Trx domains. The activity of the hybrid protein increases when exogenous TR or Trx is added, indicating an additional role for intermolecular interactions.
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PMID:Purification and functional analysis of the Mycobacterium leprae thioredoxin/thioredoxin reductase hybrid protein. 759 33

The unique antitubercular activity of isoniazid requires that the drug be oxidized by the katG-encoded mycobacterial catalase-peroxidase to an activated drug form. In order to quantitatively assess the catalytic capabilities of the enzyme, the native catalase-peroxidase from Mycobacterium smegmatis was purified over 200-fold to homogeneity. The enzyme was shown to exhibit both catalase and peroxidase activities, and in the presence of either hydrogen peroxide or t-butyl peroxide, was found to catalyze the oxidation of the reduced pyridine nucleotides, NADH and NADPH, as well as artificial peroxidase substrates, at rates between 2.7 and 20 s-1. The homogeneous enzyme exhibited a visible absorbance spectrum typical of ferric heme-containing catalase-peroxidases, with a Soret maximum at 406 nm. Low temperature (10 K) electron paramagnetic resonance spectra in the presence of ethylene glycol revealed a high spin Fe(III) signal with g values of 5.9 and 5.6. The enzyme was very slowly (t1/2 = approximately 20 min) reduced by dithionite, and the reduced form showed typical spectral changes when either KCN or CO were subsequently added. The M. smegmatis catalase-peroxidase was found to contain 2 heme molecules per tetramer, which were identified as iron protoporphyrin IX by the pyridine hemochromogen assay. The peroxidatic activity was inhibited by KCN, NaN3, isoniazid (isonicotinic acid hydrazide), and its isomer, nicotinic acid hydrazide, but not by 3-amino-1,2,4-triazole. The role of mycobacterial catalase-peroxidases in the oxidative activation of the antitubercular prodrug isoniazid is discussed.
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PMID:Purification and characterization of the Mycobacterium smegmatis catalase-peroxidase involved in isoniazid activation. 767 10

Mycobacterium sp. strain Pyr-1 cells, which were grown to the stationary phase in media with and without pyrene, were centrifuged and resuspended in a medium containing 1-nitropyrene. Cells that had been grown with pyrene oxidized up to 20% of the added 1-nitropyrene to 1-nitropyrene-cis-9,10- and 4,5-dihydrodiols. However, cells that had been grown without pyrene reduced up to 70% of the 1-nitropyrene to 1-aminopyrene but did not produce dihydrodiols. The nitroreductase activity was oxygen insensitive, intracellular, and inducible by nitro compounds. Nitroreductase activity was inhibited by p-chlorobenzoic acid, o-iodosobenzoic acid, menadione, dicumarol, and antimycin A. Extracts from cells that had been grown without pyrene activated 1-nitropyrene, 1-amino-7-nitrofluorene, 2,7-dinitro-9-fluorenone, 1,3-dinitropyrene, 1,6-dinitropyrene, and 6-nitrochrysene to DNA-damaging products, as shown in Salmonella typhimurium tester strains by the reversion assay and by induction of the umuC gene. Activation of nitro compounds, as shown by the umu test, was enhanced by NADPH. This study shows that Mycobacterium sp. strain Pyr-1 metabolizes nitroaromatic compounds by both oxidative and reductive pathways. During reduction, it generates products that are mutagenic.
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PMID:Reduction and mutagenic activation of nitroaromatic compounds by a Mycobacterium sp. 781 Oct 65

Recent developments in simultaneous multiple alignment methods of protein sequences allow prediction of structural similarity in related proteins. Alanine dehydrogenase and the N-terminal sequence of pyridine nucleotide transhydrogenase were compared for their sequences. High similarities of sequences were observed especially in their NAD(H)-binding sites. These similarities suggest that antibodies which recognized the alanine dehydrogenase of Mycobacterium tuberculosis can also be directed against the membrane bound pyridine nucleotide transhydrogenase. If this is the case, the virulent property of this pathogen could be linked to its higher synthesis of NADPH necessary for its anabolism.
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PMID:Similarities between alanine dehydrogenase and the N-terminal part of pyridine nucleotide transhydrogenase and their possible implication in the virulence mechanism of Mycobacterium tuberculosis. 843 7

The quaternary protein structure of two methanol:N,N'-dimethyl-4-nitrosoaniline (NDMA) oxidoreductases purified from Amycolatopsis methanolica and Mycobacterium gastri MB19 was analyzed by electron microscopy and image processing. The enzymes are decameric proteins (displaying fivefold symmetry) with estimated molecular masses of 490 to 500 kDa based on their subunit molecular masses of 49 to 50 kDa. Both methanol:NDMA oxidoreductases possess a tightly but noncovalently bound NADP(H) cofactor at an NADPH-to-subunit molar ratio of 0.7. These cofactors are redox active toward alcohol and aldehyde substrates. Both enzymes contain significant amounts of Zn2+ and Mg2+ ions. The primary amino acid sequences of the A. methanolica and M. gastri MB19 methanol:NDMA oxidoreductases share a high degree of identity, as indicated by N-terminal sequence analysis (63% identity among the first 27 N-terminal amino acids), internal peptide sequence analysis, and overall amino acid composition. The amino acid sequence analysis also revealed significant similarity to a decameric methanol dehydrogenase of Bacillus methanolicus C1.
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PMID:Electron microscopic analysis and structural characterization of novel NADP(H)-containing methanol: N,N'-dimethyl-4-nitrosoaniline oxidoreductases from the gram-positive methylotrophic bacteria Amycolatopsis methanolica and Mycobacterium gastri MB19. 844 87

Mycobacterium bovis BCG produces a variety of methyl-branched fatty acids. They include C28 to C32 mycocerosic acids esterified to phthiocerol and phenolphthiocerol and the shorter (C22 to C26) mycocerosic acids esterified to phthiocerol. A mycocerosic acid synthase gene-disrupted mutant was still able to produce the shorter mycocerosic acids. The enzyme short chain mycocerosic acid synthase (SMAS), that catalyzes the synthesis of such acids, was purified using anion exchange and red-agarose chromatography. Gel filtration showed the native enzyme to be a 537-kDa protein. Since SDS-polyacrylamide gel electrophoresis of the purified enzyme showed a 280-, 170-, and 100-kDa protein and they cross-reacted with antibodies prepared against the 280- or 100-kDa protein, this enzyme is composed of the three subunits or two 280-kDa monomers with an unusual susceptibility to a proteolytic nick. SMAS utilizes methylmalonyl-CoA with C12 to C20 acyl-CoA as primers and with either NADH or NADPH as the reductant to synthesize the short mycocerosic acids. The Km values for NADH and NADPH were 93 and 90 microM, respectively. Antibodies raised against either the 280- or 100-kDa protein inhibited the incorporation of methylmalonyl-CoA into fatty acids by SMAS. The enzyme is not immunologically closely related to mycocerosic acid synthase or fatty acid synthase.
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PMID:A newly identified methyl-branched chain fatty acid synthesizing enzyme from Mycobacterium tuberculosis var. bovis BCG. 944 91

Several eubacteria including Esherichia coli use an alternative nonmevalonate pathway for the biosynthesis of isopentenyl diphosphate instead of the ubiquitous mevalonate pathway. In the alternative pathway, 2-C-methyl-D-erythritol or its 4-phosphate, which is proposed to be formed from 1-deoxy-D-xylulose 5-phosphate via intramolecular rearrangement followed by reduction process, is one of the biosynthetic precursors of isopentenyl diphosphate. To clone the gene(s) responsible for synthesis of 2-C-methyl-D-erythritol 4-phosphate, we prepared and selected E. coli mutants with an obligatory requirement for 2-C-methylerythritol for growth and survival. All the DNA fragments that complemented the defect in synthesizing 2-C-methyl-D-erythritol 4-phosphate of these mutants contained the yaeM gene, which is located at 4.2 min on the chromosomal map of E. coli. The gene product showed significant homologies to hypothetical proteins with unknown functions present in Haemophilus influenzae, Synechocystis sp. PCC6803, Mycobacterium tuberculosis, Helicobacter pyroli, and Bacillus subtilis. The purified recombinant yaeM gene product was overexpressed in E. coli and found to catalyze the formation of 2-C-methyl-D-erythritol 4-phosphate from 1-deoxy-D-xylulose 5-phosphate in the presence of NADPH. Replacement of NADPH with NADH decreased the reaction rate to about 1% of the original rate. The enzyme required Mn2+, Co2+, or Mg2+ as well. These data clearly show that the yaeM gene encodes an enzyme, designated 1-deoxy-D-xylulose 5-phosphate reductoisomerase, that synthesizes 2-C-methyl-D-erythritol 4-phosphate from 1-deoxy-D-xylulose 5-phosphate, in a single step by intramolecular rearrangement and reduction and that this gene is responsible for terpenoid biosynthesis in E. coli.
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PMID:A 1-deoxy-D-xylulose 5-phosphate reductoisomerase catalyzing the formation of 2-C-methyl-D-erythritol 4-phosphate in an alternative nonmevalonate pathway for terpenoid biosynthesis. 970 69

Thiol-disulphide exchanges are involved in many important biological processes; they are normally regulated by the glutaredoxin and thioredoxin systems. The thioredoxin system (TX) is composed of thioredoxin (TrxA) and thioredoxin reductase (TrxB) and requires NADPH as a cofactor. The thioredoxin genes trxA and trxB of Mycobacterium smegmatis mc2(6) were cloned and sequenced. The complete nucleotide sequences revealed that the TX genes of M. smegmatis were clustered, similar to the organization of trxA and trxB of S. clavuligerus, M. tuberculosis and M. leprae. Alignment with the M. tuberculosis and M. leprae protein sequences showed that the deduced amino acid sequences for M. smegmatis trxA and trxB have a very high degree of similarity. Sequence alignments and phylogenetic analysis of known TrxAs and TrxBs clearly identify the two gene products of M. smegmatis as members of the TX family grouped with other mycobacteria.
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PMID:Molecular characterization of the thioredoxin system of Mycobacterium smegmatis. 979 94

Thioredoxin reductase (TrxR) catalyzes the reduction of thioredoxin (Trx) by NADPH. A unique gene organization of TrxR and Trx has been found in Mycobacterium leprae, where TrxR and Trx are encoded by a single gene and, therefore, are expressed as a fusion protein (MlTrxR-Trx). This fusion enzyme is able to catalyze the reduction of thioredoxin or 5,5'-dithiobis(2-nitrobenzoic acid) or 1, 4-naphthoquinone by NADPH, though the activity is much lower than that of Escherichia coli TrxR. It has been proposed that a large conformational change is required in catalysis of E. coli TrxR. Because the reductase portion of the enzyme from M. leprae shows significant primary structure similarity with E. coli TrxR, it is possible that MlTrxR-Trx may require a similar conformational change and that the change in conformation may be affected by the tethered Trx. The reductase has been expressed without Trx attached (MlTrxR). As reported here, comparison of the steady-state and pre-steady-state kinetics of MlTrxR-Trx with those of MlTrxR suggests that the low reductase activity of the fusion enzyme is an inherent property of the reductase, and that any steric limitation caused by the attached thioredoxin in the fusion protein makes only a minor contribution to the low activity. Titration of MlTrxR-Trx and MlTrxR with 3-aminopyridine adenine dinucleotide phosphate (AADP+), an NADP(H) analogue, results in only slight quenching of FAD fluorescence, suggesting an enzyme conformation in which the binding site of AADP+ is not close to the FAD, as in one of the conformations of E. coli TrxR.
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PMID:Thioredoxin reductase-thioredoxin fusion enzyme from Mycobacterium leprae: comparison with the separately expressed thioredoxin reductase. 981 30

The thioredoxin (Trx) and thioredoxin reductase (TR) of Mycobacterium tuberculosis have been expressed in Escherichia coli and shown to reduce peroxides and dinitrobenzenes. The reduction of H2O2 requires both Trx and TR and is more efficient under anaerobic than aerobic conditions. In contrast, cumene hydroperoxide is reduced to cumyl alcohol and acetophenone in a process that requires NADPH and TR but not Trx. Cumene hydroperoxide reduction is partially inhibited by chelation of trace metals in the medium. The reduction of cumene hydroperoxide by TR is more effective under anaerobic than aerobic conditions due to a competing oxidase reaction in which electrons are transferred from TR to O2. Under anaerobic conditions, dinitrobenzenes also serve as electron acceptors and are reduced by TR to nitroanilines, but the enzyme does not reduce mononitrobenzenes or mononitroimidazoles such as metronidazole. The reductive activity of the Trx-TR system may modify the antioxidant defenses of M. tuberculosis.
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PMID:Reduction of peroxides and dinitrobenzenes by Mycobacterium tuberculosis thioredoxin and thioredoxin reductase. 1004 95


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