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PubMed1992

Purification and characterization of an extracellular muramidase of Clostridium acetobutylicum ATCC 824 that acts on non-N-acetylated peptidoglycan.

An extracellular enzyme showing lytic activity on non-N-acetylated peptidoglycan has been isolated from Clostridium acetobutylicum ATCC 824. The lytic enzyme was purified to homogeneity by anion-exchange chromatography and gel filtration, with a recovery of 24%. The enzyme was monomeric and had an estimated molecular weight of 41,000 and an isoelectric point of 3.8. It has been characterized as a muramidase whose 23-amino-acid N terminus displayed 39% homology with the N,O-diacetyl muramidase of the fungus Chalaropsis sp. The muramidase hydrolyzed purified cell walls at an optimum pH of 3, with a maximum velocity of 9.1 mumol of reducing sugars released min-1 mg of muramidase-1 and a concentration of cell walls giving a half-maximum rate of 0.01 mg ml-1. Its activity was inhibited by glucosamine, N-acetylglucosamine, Hg2+, Fe3+, and Ag+ but not by choline. The muramidase-peptidoglycan complex rapidly dissociated before total hydrolysis of the chain and randomly reassociated on another peptidoglycan chain. The affinity of the muramidase was affected by the protein content and the acetylation of the cell wall.

Acetylation↗
PubMed1987

Immunoassay of serum muramidase (lysozyme) in ocular diseases.

Serum levels of muramidase activity were measured in 162 patients with different ocular diseases and 84 healthy subjects by electro-immuno-diffusion technique. We demonstrated for the first time that electro-immuno-diffusion technique could be successfully applied for the estimation of serum muramidase concentrations. Serum muramidase was found to be high in significant number of cases with granulomatous uveitis, tuberculous keratitis, central serous retinopathy and Eales' disease. Tuberculosis was presumed to be the cause in them by the process of exlusion. Patients with high serum muramidase activity were subjected to anti-tubercular treatment with a marked clinical improvement. It is suggested that high serum muramidase could be an useful parameter in deciding the line of treatment in patients with ocular diseases of uncertain etiology. Serum muramidase concentrations showed return to normal levels with the clinical improvement of the diseases with treatment. It increased again with the re-appearance of the activity of the diseases.

Eye Diseases↗
PubMed1992

The autolytic ('suicidase') system of Enterococcus hirae: from lysine depletion autolysis to biochemical and molecular studies of the two muramidases of Enterococcus hirae ATCC 9790.

Autolysis of Enterococcus hirae ATCC 9790 is the result of the action of endogenous enzymes that hydrolyze bonds in the protective and shape-maintaining cell wall peptidoglycan. It is thought that these potentially suicidal enzymes play a positive role(s) in wall growth and division and are expressed as autolysins when cell wall assembly and/or repair are inhibited. E. hirae possesses two potentially autolytic enzymes, both of which are muramidases. Although they hydrolyze the same bond as hen egg-white lysozyme, both are high-molecular-mass, complex enzymes. Muramidase-1 is synthesized as a zymogen, requiring protease activation. It is a glucoenzyme that is also multiply nucleotidylated with an unusual nucleotide, 5-mercaptouridine monophosphate. Muramidase-2 is almost certainly a product of a separate gene. The deduced amino acid sequence of a cloned gene for extracellular muramidase-2 showed several unusual features. It appears to be a two-, or perhaps three-domain protein with a putative glycosidase-active site near the N-terminal end and six 45-amino-acid-long repeats at the C-terminal end which are presumed to be involved with high-affinity binding to the insoluble peptidoglycan substrate. Muramidase-2 binds penicillin with low affinity. The presence of several amino acid groupings characteristic of serine-active site beta-lactam-interactive proteins is consistent with the possible presence of a penicillin-binding, third domain. Indirect evidence consistent with a role(s) for these enzymes in cell wall growth and division has been obtained. However, proof of such role(s) awaits modern genetic, molecular, and biochemical analyses.

Amino Acid Sequence↗
PubMed1995

Identification of a gene (arpU) controlling muramidase-2 export in Enterococcus hirae.

Muramidase-2 of Enterococcus hirae is a 74-kDa peptidoglycan hydrolase that plays a role in cell wall growth and division. To study its regulation, we isolated a mutant defective in muramidase-2 release under certain growth conditions. This mutant had cell walls which apparently lacked 74-kDa muramidase-2 but which accumulated two proteolytic fragments of 32 and 43 kDa, which exhibited muramidase-2 activity in the membrane fraction. By complementation cloning, we identified a 2.6-kb fragment of the E. hirae chromosome containing a gene cluster coding for proteins of 58 to 137 amino acids. One of these genes (arpU), which encoded a 15.9-kDa protein, was shown to complement the defect of the A9 mutant in trans. We propose that this gene may be involved in the regulation of muramidase-2 export.

Amino Acid Sequence↗
PubMed1997

Molecular characterization of a germination-specific muramidase from Clostridium perfringens S40 spores and nucleotide sequence of the corresponding gene.

The exudate of fully germinated spores of Clostridium perfringens S40 in 0.15 M KCI-50 mM potassium phosphate (pH 7.0) was found to contain another spore-lytic enzyme in addition to the germination-specific amidase previously characterized (S. Miyata, R. Moriyama, N. Miyahara, and S. Makino, Microbiology 141:2643-2650, 1995). The lytic enzyme was purified to homogeneity by anion-exchange chromatography and shown to be a muramidase which requires divalent cations (Ca2+, Mg2+, or Mn2+) for its activity. The enzyme was inactivated by sulfhydryl reagents, and sodium thioglycolate reversed the inactivation by Hg2+. The muramidase hydrolyzed isolated spore cortical fragments from a variety of wild-type organisms but had minimal activity on decoated spores and isolated cell walls. However, the enzyme was not capable of digesting isolated cortical fragments from spores of Bacillus subtilis ADD1, which lacks muramic acid delta-lactam in its cortical peptidoglycan. This indicates that the enzyme recognizes the delta-lactam residue peculiar to spore peptidoglycan, suggesting an involvement of the enzyme in spore germination. Immunochemical studies indicated that the muramidase in its mature form is localized on the exterior of the cortex layer in the dormant spore. A gene encoding the muramidase, sleM, was cloned into Escherichia coli, and the nucleotide sequence was determined. The gene encoded a protein of 321 amino acids with a deduced molecular weight of 36,358. The deduced amino acid sequence of the sleM gene indicated that the enzyme is produced in a mature form. It was suggested that the muramidase belongs to a separate group within the lysozyme family typified by the fungus Chalaropsis lysozyme. A possible mechanism for cortex degradation in C. perfringens S40 spores is discussed.

Amino Acid Sequence↗
PubMed1981

Muramidase content of cells in human granulomatous reactions.

The muramidase content of reactive cells in the lesions of human foreign body reactions, lepromatous and tuberculoid leprosy, sarcoidosis, tuberculosis, and granulomatous hepatitis, was assessed using specific anti-human muramidase antiserum and a peroxidase-anti-peroxidase marker system. Epithelioid and giant cells in sarcoidosis, tuberculosis, granulomatous hepatitis, and tuberculoid leprosy all showed the presence of muramidase in their cytoplasm. The muramidase content of macrophages in foreign body reactions and lepromatous leprosy varied and most multinucleate cells in these lesions gave a negative reaction. Possibly varying rates of muramidase secretion may account for these differences.

Cytoplasm↗
PubMed1985

Muramidase (lysozyme) findings in sural and radial nerve biopsies in leprosy patients after varying periods of treatment.

Using the immunoperoxidase staining method, tissue muramidase (lysozyme) activity was studied in 34 nerve biopsies from leprosy patients and compared to findings in the skin. In a majority of lepromatous and borderline-lepromatous leprosy patients, the enzyme was seen to form a saccular pattern within the cells; whereas a granular pattern was found at the tuberculoid end of the leprosy spectrum, as well as during reversal reactions. Indeed, the most intense enzymatic activity was found in four patients with reversal reactions. Compared to the skin, muramidase activity was found to be more intense and persisted longer in the nerves. Successful antileprosy treatment reduced the enzymatic activity in both the nerves and the skin, but more so in the skin. Schwann cells and axons did not show muramidase activity, indicating that the muramidase-positive cells are not of neuronal origin. Our results suggest that a high percentage of mononuclear cells infiltrating the peripheral nerves in leprosy are derived from blood monocytes. The function of tissue muramidase in leprosy is not yet clear. Its peculiar intracellular distribution pattern in the different forms of leprosy, however, warrants further study to elucidate its role in the pathogenesis of the disease.

Adolescent↗
PubMed2004

Two novel muramidases from skin mucosa of rainbow trout (Oncorhynchus mykiss).

Two novel antibacterial muramidases were purified to homogeneity from skin exudates of rainbow trout (Oncorhynchus mykiss). Unusually, one has an acidic isoelectric point and it is the first anionic muramidase to be reported for fish. Its molecular mass is 14,268 Da, as determined by mass spectrometry. The other muramidase is cationic with a mass of 14,252 Da. Partial N-terminal amino acid sequencing and peptide mapping strongly point to it being a c-type lysozyme, the first to be purified and characterised from skin of a salmonid. Its optimum pH ranges from 4.5 to 5.5 and its optimum temperature, at pH 5.0, is 33-49 degrees C, although it still exhibits activity at 5 degrees C. It is strongly bactericidal to the Gram-(+) bacterium Planococcus citreus, with a minimum bactericidal concentration of 100 U ml(-1), but is neither chitinolytic nor haemolytic. These two muramidases probably contribute to epithelial defence of the fish against microbes, either alone or in synergism with antibacterial peptides.

Amino Acid Sequence↗
PubMed1978

[Comparative study of the muramidase (lysozyme) activity in the blood cells of laboratory and agricultural animals].

Comparative studies have been carried out on the blood of certain laboratory and farm animals and birds, whereby the activity of muramidase (lysozyme) is established in neutrophilic cells of mice, guinea pigs, rats, rabbits, dogs, hens, turkeys and geese and in the monocytes of rabbits and dogs. The percentage of cells with muramidase activity manifests species features. No cells with a presence of muramidase activity have been found in the perypheral blood of cattle, sheep, pigs, goats, horses and bullalos. Certain questions of a general biological aspect about the origin of muramidase in the blood serum are examined on the basis of the results obtained and recent data from analyses of human blood.

Animals↗
PubMed2001

The role in flagellar rod assembly of the N-terminal domain of Salmonella FlgJ, a flagellum-specific muramidase.

The C-terminal half of the Salmonella flagellar protein FlgJ has peptidoglycan hydrolyzing activity and it has been suggested that it is a flagellum-specific muramidase which locally digests the peptidoglycan layer to permit assembly of the rod structure to proceed through the periplasmic space. It was also suggested that FlgJ might be involved in rod formation itself, although there was no direct evidence for this. We purified basal body structures from SJW1437(flgJ) transformed with plasmids encoding various mutant FlgJ proteins and found that these basal bodies possessed the periplasmic P ring but lacked the outer membrane L ring; they also lacked a hook at their distal end. All of these mutant FlgJ proteins had an altered or missing C-terminal domain but had at least the first 151 amino acid residues of the N-terminal domain. Immunoblotting analysis of fractionated cell extracts revealed that a rod/hook export class protein, FlgD, was exported to the periplasm but not to the culture supernatant in these mutants. FlgJ was shown to physically interact with several proteins, and especially FliE and FlgB, which are believed to reside at the cell-proximal end of the rod. On the basis of these results, we conclude that the N-terminal 151 amino acid residues of FlgJ are directly involved in rod formation and that the muramidase activity of FlgJ, though needed for formation of the L ring and subsequent events such as hook formation, is not essential for rod or P ring formation. In contrast, muramidase activity alone does not support rod assembly.

Bacterial Proteins↗
PubMed1984

Chloroquine-induced inhibition of rat serum muramidase activity in vivo in relation to tissue changes.

Chloroquine was tested for its inhibitory effect in vivo on the activities of rat serum and tissue muramidase. Daily administration of this anti-malarial drug to rats resulted in an appreciable reduction of kidney and liver enzyme activities 1 day after the first dose. No corresponding increases in enzyme activity were detected in the serum of treated animals up to day 9 when muramidase activity was then significantly reduced. Activity observed in the heart tissue was not affected until day 12, when the level was significantly reduced. These results suggest that chronic chloroquine administration to rats may result in an extensive inhibition of muramidase activity probably at the cellular/molecular level.

Animals↗
PubMed1981

Occurrence and patterns of muramidase containing cells in Hodgkin's disease, non-Hodgkin's lymphomas, and reactive hyperplasia.

The occurrence and pattern of cytoplasmic muramidase containing histiocytes were studied by the unlabeled antibody peroxidase-antiperoxidase method in biopsy material from patients with Hodgkin's disease, non-Hodgkin's lymphomas, and reactive hyperplasia. The majority of lymph nodes from patients with Hodgkin's disease, nodular lymphoma, and reactive hyperplasia gave positive staining reactions when tested in this manner. Differences in the staining pattern were observed for the different conditions studied. In general, stain positive cells occurred in one of the following four patterns: nodular, dispersed, aggregating without background stain, or aggregating with background stain (mottling pattern). The nodular and aggregating without background stain patterns were not specific and were seen in various conditions. The dispersed pattern, however, was observed only in some cases of non-Hodgkin's diffuse lymphomas, suggesting a subgroup of tumors characterized by active participation of reactive histiocytes. The mottling pattern was virtually limited to Hodgkin's disease. Since the mottling pattern appeared to be produced by virtue of a large amount of extracellular muramidase, the elevation of the serum muramidase level in Hodgkin's disease may be related to enzymatically active secretory histiocytes. Moreover, the mottling staining pattern was observed frequently in the lymphocytic predominance and nodular sclerosis type of Hodgkin's disease, but relatively infrequently in the mixed cellularity or lymphocytic depletion types, suggesting that the variation in histiocytic activity may be related to the course of the disease. The decreased staining reaction observed in the latter two categories could not be accounted for by a decrease in the numbers of histiocytic cells in hematoxylin and eosin stained sections, suggesting that release or synthesis may be defective in those unfavorable types of Hodgkin's disease.

Cytoplasm↗
PubMed2004

Comparison of the microbicidal and muramidase activities of mouse lysozyme M and P.

Lysozyme is one of the most abundant antimicrobial proteins in the airspaces of the lung. Mice express two lysozyme genes, lysozyme M and P, but only the M enzyme is detected in abundance in lung tissues. Disruption of the lysozyme M locus significantly increased bacterial burden and mortality following intratracheal infection with a Gram-negative bacterium. Unexpectedly, significant lysozyme enzyme activity (muramidase activity) was detected in the airspaces of uninfected lysozyme M-/- mice, amounting to 25% of the activity in wild-type mice. Muramidase activity in lysozyme M-/- mice was associated with increased lysozyme P mRNA and protein in lung tissue and bronchoalveolar lavage fluid respectively. The muramidase activity of recombinant lysozyme P was less than that of recombinant M lysozyme. Recombinant P lysozyme was also less effective in killing selected Gram-negative bacteria, requiring higher concentrations than lysozyme M to achieve the same level of killing. The lower antimicrobial activity of P lysozyme, coupled with incomplete compensation by P lysozyme in lysozyme M-/- mice, probably accounts for the increased susceptibility of null mice to infection. Recombinant lysozyme M and P were equally effective in killing selected Gram-positive organisms. This outcome suggests that disruption of both M and P loci would significantly increase susceptibility to airway infections, particularly those associated with colonization by Gram-positive organisms.

Amino Acid Sequence↗
PubMed1997

Production and detection of muramidase and acetylglucosaminidase from Agaricus bisporus.

The production and regulation of extracellular bacteriolytic enzymes of Agaricus bisporus are being studied to understand better the nutrition of this fungus and to identify factors that regulate the selectivity of mushroom compost as a growth medium. Both muramidase (EC.3.2.1.17) and N-acetyl-beta-D-glucosaminidase (beta-GlcNAcase, EC.3.2.1.30) have been detected in liquid cultures of A. bisporus, and in cultures fruiting in sterile and non-sterile compost. A turbidometric assay, based on the decrease in optical density of suspended Bacillus subtilis bacterial cell walls, was used to measure muramidase production by A. bisporus. A colorimetric assay was used to measure beta-GlcNAcase. Both bacteriolytic enzyme activities were produced on a range of sole carbon sources, including killed freeze-dried B. subtilis cells. Muramidase activity was highest in axenic compost cultures. Bacteriolytic enzyme activity peaked as the first group of fruit bodies was harvested in both sterile and non-sterile compost.

Acetylglucosaminidase↗
PubMed1980

Detection of muramidase (lysozyme)-secreting leucocytes at the single-cell level by a protein A plaque assay.

Using a modification of the protein A plaque assay, muramidase (lysozyme)-producing leucocytes were detected as plaque-forming cells. In the presence of anti-muramidase Ig and complement the secreted lysozyme resulted in lysis of protein-A-coated target erythrocytes. By the use of a monolayer technique individual plaque-forming cells could be identified by staining procedures. Granulocytes as well as monocytes were found to produce muramidase and thus to form plaques. This method could serve as a useful tool when studying lysozyme secretion. Furthermore, by the use of appropriate antisera, this method could be employed for the study of any cell type (any secretion), provided enough molecules are being secreted.

Cells, Cultured↗
PubMed2000

Effects of a muramidase on a mixed bacterial community.

In bacterial communities one bacterium can influence the growth of other members of the population. These interactions may be based on nutritional factors or may occur via bacterial signaling molecules that are released in the medium. We present an example, showing that in addition to the above means of interactions, muramidases, enzymes that specifically cleave peptidoglycan chains, can also mediate interactions between bacteria. Using fluorescent in situ hybridization we demonstrate that Lactococcus lactis muramidase AcmA can hydrolyze the cell wall of Streptococcus thermophilus, without affecting viability. This intercellular activity of the lactococcal muramidase results in chain disruption of streptococci in vivo. Our data lead us to propose that chains can give growth advantages to streptococci in aerobic conditions.

Aerobiosis↗
PubMed1992

Cloning and sequence analysis of the muramidase-2 gene from Enterococcus hirae.

Extracellular muramidase-2 of Enterococcus hirae ATCC 9790 was purified to homogeneity by substrate binding, guanidine-HCl extraction, and reversed-phase chromatography. A monoclonal antibody, 2F8, which specifically recognizes muramidase-2, was used to screen a genomic library of E. hirae ATCC 9790 DNA in bacteriophage lambda gt11. A positive phage clone containing a 4.5-kb DNA insert was isolated and analyzed. The EcoRI-digested 4.5-kb fragment was cut into 2.3-, 1.0-, and 1.5-kb pieces by using restriction enzymes KpnI, Sau3AI, and PstI, and each fragment was subcloned into plasmid pJDC9 or pUC19. The nucleotide sequence of each subclone was determined. The sequence data indicated an open reading frame encoding a polypeptide of 666 amino acid residues, with a calculated molecular mass of 70,678 Da. The first 24 N-terminal amino acids of purified extracellular muramidase-2 were in very good agreement with the deduced amino acid sequence after a 49-amino-acid putative signal sequence. Analysis of the deduced amino acid sequence showed the presence at the C-terminal region of the protein of six highly homologous repeat units separated by nonhomologous intervening sequences that are highly enriched in serine and threonine. The overall sequence showed a high degree of homology with a recently cloned Streptococcus faecalis autolysin.

Amino Acid Sequence↗
PubMed1974

Blood muramidase activity in colorectal cancer.

The serum muramidase levels were measured in 128 patients with primary or metastatic colorectal cancer, 166 tumour-free patients after resection of a colorectal cancer, and 172 controls. Muramidase levels over 10 mug/ml were detected in 30%-39% of the tumour-bearing patients, in 8.2% of the tumour free, and in only 1.7% of the controls (normal level 6.68 +/- 1.42 mug/ml). Long-term follow up indicated that raised levels may occur as a transient phenomenon in recurrent or metastatic disease. The likely relation of abnormal serum muramidase activity and stimulation of the reticuloendothelial system is discussed.

Adenocarcinoma↗