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Query: UMLS:C0026918 (Mycobacterium)
 52,428 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The positions of double bond in the monounsaturated C15-C32 fatty acids of Mycobacterium tuberculosis H37Ra were established by gas chromatography/mass spectrometry of the ozonized esters and their pyrrolidide derivatives. The monounsaturated C15-C21 fatty acids had the double bond primarily at the delta 9 position while the monounsaturated longer chain fatty acids (C22-C32) had the double bond in several positions. Many of the latter acids, especially the odd-numbered series, were very complex isomeric mixtures. Quantitation showed the most abundant even-numbered long chain fatty acid isomers to be as follows: C22, delta 4; C24, delta 5; C26, delta 7 and delta 9; C28, delta 9; C30, delta 11 and delta 13; C32, delta 13 and delta 15.
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PMID:Isolation and characterization of the monounsaturated long chain fatty acids of Mycobacterium tuberculosis. 10 28

The positions of esterification of the 4 to 5 acetyl residues in the acetylated methylmannose-containing polysaccharide from Streptomyces griseus have been established by the methyl replacement technique, wherein ester substituents are specifically replaced with methyl ether substituents. The newly incorporated methyl groups were distinguished from 3-O-methyl groups by the use of polysaccharide containing radioactively labeled endogenous methyl groups. The positions of methyl group localization were established by a proton magnetic resonance study of the intact methyl-replaced polysaccharide combined with an analysis of the constituent monosaccharides by gas-liquid chromatography-electron impact mass spectrometry of their alditol acetate derivatives. These studies demonstrate that the acetyl groups are located at position 6 of approximately half of the 10 contiguous alpha(1 leads to 4)-linked 3-O-methyl-D-mannose residues. Purification of the polysaccharide was accomplished by an added step involving affinity chromatography on a column containing immobilized palmitoyl residues. The affinity of the polysaccharide for this long chain lipid suggests that its plays a role similar to the methylmannose-containing polysaccharide of Mycobacterium smegmatis in its regulation of the bacterium's fatty acid synthetase.
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PMID:Acetylated methylmannose polysaccharide of Streptomyces griseus. Locations of the acetyl groups. 10 71

The initial steady state rate and product distribution of fatty acid synthesis catalyzed by Mycobacterium smegmatis fatty acid synthetase has been investigated as a function of various concentrations of acetyl-CoA, malonyl-CoA, mycobacterial polysaccharide, and bovine serum albumin. Polysaccharide has a large effect on both rate and chain length. The steady state rate stimulation by polysaccharide is not duplicated by other acyl-CoA-binding molecules such as bovine serum albumin. It is concluded that relief of product inhibition does not adequately explain the specific effects of the mycobacterial polysaccharide. A general mechanism is presented which accounts for variations in reaction rate and produce pattern over a wide range of experimental conditions. We propose that the diffusion of long chain acyl-CoA (C14 to C24) from the enzyme is the rate-limiting step in fatty acid synthesis catalyzed by the M. smegmatis synthetase. Polysaccharide facilitates this rate-limiting step by forming a ternary complex with enzyme-bound acyl-CoA causing rapid release of product.
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PMID:Mycobacterium smegmatis fatty acid synthetase. A mechanism based on steady state rates and product distributions. 88 80

Homogenates were prepared from three sources, Mycobacterium smegmatis Saccharomyces cerevisiae and Escherichia coli and tested for docosyl malonyl-CoA-ACP transacylase activity, using ACP purified from E. coli strain B and [2R, 2S, 1, 3-14C2] docosyl malonyl-CoA synthesized chemically, as substrates. Only homogenates of M. semegmatis showed positive transacylase activity. Successive chromatographies on Sephadex G-150 and then on DEAE-Sephadex A-50 prove that neither the palmityl-CoA-ACP-transacylase nor the malonyl-CoA-ACP-transacylase of M. smegmatis are responsible for this activity. The question concerning the identity of the enzyme with one of the two entities exhibiting acetyl-CoA-ACP-transacylase activity, previously identified in homogenates of this microorganism (1973 this journal, 55, 1381-1394), remains open for further experimentation. The physiological significance of the presence of a long chain alkyl malonyl-CoA-ACP-transacylase in homogenates of M. smegmatis, a representative of the Actinomycetales, is discussed in relation to the mechanism of the biosynthesis of mycolic acids. Chromatography on Sephadex G-100 showed that the substrate of the enzyme, docosyl malonyl-CoA, exists, in 50 mu molar aqueous solution, mostly in an aggregated state. A factor has been identified in the homogenates, which in the presence of radioactive docosyl malonyl-CoA, leads to the formation of a radioactive material showing an apparent molecular weight less than 10000. The nature of this material is discussed.
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PMID:Further analysis of acyl-CoA-ACP-transacylases of mycobacterium smegmatis. Identification of a long chain alkyl malonyl-CoA-ACP-transacylase. 110 74

A radiometric assay system has been used to study oxidation patterns of [1-14C]fatty acids and [U-14C]L-amino acids by drug-susceptible and drug-resistant organisms of the genus Mycobacterium. Two strains of M. tuberculosis susceptible to all drugs, H37Rv TMC 102 and Erdman, were used. Drug-resistant organisms included in this investigation were M. tuberculosis H37Rv TMC 303, M. bovis, M. avium, M. intracellulare, M. kansasii and M. chelonei. The organisms were inoculated into a sterile system containing liquid 7H9 medium along with one of the [1-14C]fatty acids or [U-14C]L-amino acids. Although each individual organism displayed a different pattern of fatty acid oxidation, these patterns were not distinctive enough for identification of the organism. Susceptible and resistant mycobacteria did not display any preferential oxidation of long chain or of short chain fatty acids that might help to distinguish these organisms. As with the fatty acid series, differential oxidation patterns for amino acids could be recognized, but again these patterns were not distinctive enough to identify each organism. Complex amino acids such as proline, phenylalanine and tyrosine were of no use in identification of mycobacteria, since virtually all organisms failed to oxidize them. Identification of each individual organism was feasible using a combination of fatty acids and amino acids which included butyric, octanoic, oleic, glycine and alanine. There was no combination of substrates able to separate susceptible and resistant organisms.
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PMID:Radiometric studies on the oxidation of [1-14C]fatty acids and [U-14C]L-amino acids by mycobacteria. 358 54

The multienzyme complex from Mycobacterium phlei which catalyzes the synthesis of long chain fatty acids from acetyl-CoA and malonyl-CoA requires a heat-stable fraction (stimulating factor, SF) for activity. Fractionation of heat-treated M. phlei extracts affords two stimulatory subfractions, one of which (SF(2)) can be replaced by FMN. The other (SF(1)) is further separable into 3 polysaccharides (PS(I), PS(II), and PS(III)). PS(I) contains about 95% 3-O-methylmannose and 5% mannose; the sugar composition of PS(II) and PS(III) is about 55% 6-O-methylglucose and 45% glucose for both. Each of the three purified polysaccharides, in combination with FMN, substitutes for the crude stimulating factor. The polysaccharides exert their effect on the fatty acid synthetase by lowering the K(m) for acetyl-CoA about 50-fold.
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PMID:Fatty acid synthetase activity in Mycobacterium phlei: regulation by polysaccharides. 527 5

An esterase activity hydrolyzing palmitoyl-CoA was released into the culture medium from Mycobacterium smegmatis. Although another esterase activity hydrolyzing Tween 20 (polyoxyethylene sorbitan monolaurate) was also found in the culture medium, the bulk of the esterase activity was retained in the cells. However, treatment of early-log phase cells with lysozyme to prepare ghosts released 80% of the Tween 20 hydrolyzing activity, indicating the localization of the esterase in the periplasmic space or the cell envelope fraction. The presence of two different esterases hydrolyzing palmitoyl-CoA and Tween 20, suggested by the above results, was confirmed by the separation of these esterases on phenyl-Sepharose column chromatography. Palmitoyl-CoA hydrolase (thioesterase) was purified 630-fold from lysozyme-treated supernatant fluid to homogeneity, by means of Sephadex G-100 gel filtration, and DEAE-cellulose, phenyl-Sepharose and Blue-Agarose column chromatographies. Its molecular weight was approximately 42,000. Tween hydrolase was partially purified 150-fold by the same purification procedure up to the step of phenyl-Sepharose chromatography and its molecular weight was found to be about 51,000. These activities were stable against heating at 60 degrees C and treatment with non-ionic detergents. Thioesterase hydrolyzed long chain acyl-CoAs (C12-C20), but not Tween 20-80 or beta-naphthyl acetate. On the other hand, Tween hydrolase hydrolyzed Tween 20-80 and beta-naphthyl acetate. On the other hand, Tween hydrolase hydrolyzed Tween 20-80 and beta-naphthyl acetate, but not acyl-CoAs. Both esterases hydrolyzed monoolein, but not diolein, triolein, or phosphatidylcholine.
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PMID:Two esterases released from Mycobacterium smegmatis from the hydrolysis of long chain acyl-CoAs and Tween. 733 1

Some time ago, it was found that attachment of hydrophilic polyoxyethylene chains to various hydrophobic phenols and alcohols gave water-soluble products which, although inactive in vitro, influenced and experimental tuberculous infection. With short chains the infection was suppressed, and with long chains it was promoted. Later work concentrated on Macrocyclon (short chain) and HOC-60 (long chain), both derived from a hydrophobic, polyphenolic calixarene. Growth of Mycobacterium tuberculosis inside macrophages (M phi) was inhibited by Macrocyclon and stimulated by HOC-60. Also, triglyceride lipase from M phi extracts and an extracellular phospholipase were inhibited by Macrocyclon and stimulated by HOC-60. This suggestion of a mechanism has been strengthened by the finding that M phi cultivated in monolayers and treated with Macrocyclon showed accumulation of lipid and little formation of fatty acid after incubation of killed cells. With HOC-60, lipid was depleted and much fatty acid was found.
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PMID:Calixarenes with host-mediated potency in experimental tuberculosis: further evidence that macrophage lipids are involved in their mechanism of action. 860 27

Mycobacterial cell walls contain unique lipids such as mycolic acids, very long chain fatty acids and multimethyl-branched fatty acids. A multifunctional fatty acid synthase (Fas) with the unique capability of catalyzing both de novo synthesis and chain elongation of fatty acids has been purified and characterized from Mycobacterium tuberculosis var. bovis BCG (Bacillus Calmette-Geurin) [Kikuchi et al., Arch. Biochem. Biophys. 295 (1992) 318-326]. To understand how the various domains that catalyze the reactions involved in both de novo synthesis and elongation are organized in the mycobacteria, a fas gene was cloned from a cosmid library of genomic DNA from M. bovis BCG. Sequencing of the cosmid clone revealed a contiguous sequence of 11 577 bp of mycobacterial genome containing a 8389-bp open reading frame that could code for a protein of 2797 amino acids (301 kDa). By comparing the Fas aa sequence with the sequences in the active site regions of known fas and polyketide synthase-encoding genes, the functional catalytic domains in Fas were identified. This analysis revealed that the domains are organized in the following order: acyltransferase, enoyl reductase, dehydratase, malonyl/palmitoyl transferase, acyl carrier protein, beta-keto reductase, beta-ketoacyl synthase. This domain organization is like a head to tail fusion of the two yeast fas gene subunits. The results obtained constitute the first report of the cloning, sequencing and structural elucidation of a fas from the Mycobacteria.
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PMID:Cloning, sequencing and characterization of a fatty acid synthase-encoding gene from Mycobacterium tuberculosis var. bovis BCG. 862 Oct 98

A single gene (mas) encodes the multifunctional enzyme that catalyzes the synthesis of very long chain multiple methyl branched fatty acids called mycocerosic acids that are present only in slow-growing pathogenic mycobacteria and are thought to be important for pathogenesis. To achieve a targeted disruption of mas, an internal 2-kb segment of this gene was replaced with approximately the same size hygromycin-resistance gene (hyg), such that hyg was flanked by 4.7- and 1.4-kb segments of mas. Transformation of Mycobacterium bovis BCG with this construct in a plasmid that cannot replicate in mycobacteria yielded hygromycin-resistant transformants. Screening of 38 such transformants by PCR revealed several transformants representing homologous recombination with single crossover and one with double crossover. With primers representing the hyg termini and those representing the mycobacterial genome segments outside that used to make the transformation construct, the double-crossover mutant yielded PCR products expected from either side of hyg. Gene replacement was further confirmed by the absence of the vector and the 2-kb segment of mas replaced by hyg from the genome of the mutant. Thin-layer and radio-gas chromatographic analyses of the lipids derived from [1-14C]propionate showed that the mutant was incapable of synthesizing mycocerosic acids and mycosides. Thus, homologous recombination with double crossover was achieved in a slow-growing mycobacterium with an intron-containing RecA. The resulting mas-disrupted mutant should allow testing of the postulated roles of mycosides in pathogenesis.
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PMID:Targeted replacement of the mycocerosic acid synthase gene in Mycobacterium bovis BCG produces a mutant that lacks mycosides. 864 81


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