Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.17 (lysozyme)
 21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An alanine racemase (EC 5.1.1.1) mutant (Dal-) of Bacillus subtilis required small amounts of D-alanine to synthesize an osmotically stable cell wall in certain growth media. Investigation of the conditions which caused lysis in hypotonic media revealed that in addition to complex media, such as nutrient broth and acid-hydrolyzed casein, glycine inhibited stable cell wall formation. D-Alanine prevented the glycine inhibition. Up to 99% lysis occurred in both dilute and dense cell suspensions (optical densities up to 110) within 2.5 h after adding 1% glycine to late log phase cultures. Intracellular enzymes recovered from the lysate were as active as those from lysozyme-disrupted cells. No amino acid tested other than glycine induced lysis. Dal- mutants can be used for controlled lysis of bacterial cells to facilitate the isolation of normal intracellular constituents and bioengineered products from fermentation processes. Cell walls of most bacteria contain D-alanine; thus, this strategy should be applicable to a wide variety of microorganisms.
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PMID:Controlled lysis of bacterial cells utilizing mutants with defective synthesis of D-alanine. 313 14

A mutant of Escherichia coli has been found to have an increased sensitivity to actinomycin D and to sodium deoxycholate and an unusual morphology which accompanies an abnormality in cellular division. All of these characteristics are suppressed when the strain is grown in the presence of d-alanine. This strain, called MAD-1, for murein altered division mutant, exhibits its pleiotropic phenotype only when certain carbon compounds are used as energy sources in minimal medium. Nonpermissive carbon sources, which elicit the disturbed phenotype, include glucose, mannitol, fructose, maltose, and lactose; permissive carbon sources include galactose, glycerol, lactate, and succinate. The mutant is able to transport nonpermissive carbon compounds; 3 mM 3',5'-cyclic adenosine monophosphate included in the medium does not alter the phenotype seen with growth on glucose. Deoxyribonucleic acid and protein synthesis are normal with respect to cellular mass increase. d-Alanine specifically suppresses the pleiotropic phenotype at a concentration six times lower than l-alanine, the only other compound found to be effective. There is no abnormality in the K(m) or V(max) of l-alanine racemase or d-alanine-d-alanine synthetase of MAD-1 compared to its parent, CR34. MAD-1 is more susceptible to growth inhibition by penicillin or cycloserine than its parent, and is exquisitely sensitive to lysis in the presence of sodium deoxycholate or lysozyme. When cell wall biosynthesis is inhibited, MAD-1 lyses much more rapidly than CR34, even after it has been phenotypically suppressed by growth on d-alanine. The incorporation of l-alanine and diaminopimelic acid into the peptidoglycan of the mutant and wild type is identical; d-alanine is incorporated 1.5 times more rapidly into MAD-1 cells grown under nonpermissive conditions. The peptidoglycan fragments seen after digestion with lysozyme were similar for MAD-1 and the wild type. The results are interpreted as being compatible with an increased autolytic rate in MAD-1, caused either by an increase in the quantity or activity of an autolysin, or by an abnormal cell wall which is especially susceptible to autolysis, but which was not detected by analysis of peptidoglycan fragments.
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PMID:Relationship between permeability, cell division, and murein metabolism in a mutant of Escherichia coli. 426 3

In the present study, peptidoglycan from Rickettsia prowazekii, an obligate intracellular bacterium, was purified. The rickettsial peptidoglycan is like that of gram-negative bacteria; that is, it is sodium dodecyl sulfate insoluble, lysozyme sensitive, and composed of glutamic acid, alanine, and diaminopimelic acid in a molar ratio of 1.0:2.3:1.0. The small amount of lysine found in the peptidoglycan preparation suggests that a peptidoglycan-linked lipoprotein(s) may be present in the rickettsiae. D-Cycloserine, a D-alanine analog which inhibits the biosynthesis of bacterial cell walls, prevented rickettsial growth in mouse L929 cells at a high concentration and altered the morphology of the rickettsiae at a low concentration. These effects were prevented by the addition of D-alanine. This suggests that R. prowazekii contains D-alanine in the peptidoglycan and has D-Ala-D-Ala ligase and alanine racemase activities.
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PMID:Analysis of the peptidoglycan of Rickettsia prowazekii. 830 May 46

d-Alanine is a structural component of mycobacterial peptidoglycan. The primary route of d-alanine biosynthesis in eubacteria is the enantiomeric conversion from l-alanine, a reaction catalysed by d-alanine racemase (Alr). Mycobacterium smegmatis alr insertion mutants are not dependent on d-alanine for growth and display a metabolic pattern consistent with an alternative pathway for d-alanine biosynthesis. In this study, we demonstrate that the M. smegmatis alr insertion mutant TAM23 can synthesize d-alanine at lower levels than the parental strain. The insertional inactivation of the alr gene also decreases the intracellular survival of mutant strains within primary human monocyte-derived macrophages. By complementation studies, we confirmed that the impairment of alr gene function is responsible for this reduced survival. Inhibition of superoxide anion and nitric oxide formation in macrophages suppresses the differential survival. In contrast, for bacteria grown in broth, both strains had approximately the same susceptibility to hydrogen peroxide, acidified sodium nitrite, low pH and polymyxin B. In contrast, TAM23 exhibited increased resistance to lysozyme. d-Alanine supplementation considerably increased TAM23 viability in nutritionally deficient media and within macrophages. These results suggest that nutrient deprivation in phagocytic cells combined with killing mediated by reactive intermediates underlies the decreased survival of alr mutants. This knowledge may be valuable in the construction of mycobacterial auxotrophic vaccine candidates.
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PMID:Impairment of D-alanine biosynthesis in Mycobacterium smegmatis determines decreased intracellular survival in human macrophages. 1938 14