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Results for “MURAMIDASE”

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At least 127 records · Page 7Linked to original sources
PubMed1994

Doughnut-shaped structure of a bacterial muramidase revealed by X-ray crystallography.

The integrity of the bacterial cell wall depends on the balanced action of several peptidoglycan (murein) synthesizing and degrading enzymes. Penicillin inhibits the enzymes responsible for peptide crosslinks in the peptidoglycan polymer. Enzymes that act solely on the glycosidic bonds are insensitive to this antibiotic, thus offering a target for the design of antibiotics distinct from the beta-lactams. Here we report the X-ray structure of the periplasmic soluble lytic transglycosylase (SLT; M(r) 70,000) from Escherichia coli. This unique bacterial exomuramidase cleaves the beta-1,4-glycosidic bonds of peptidoglycan to produce small 1,6-anhydromuropeptides. The structure of SLT reveals a 'superhelical' ring of alpha-helices with a separate domain on top which resembles the fold of lysozyme. Site-directed mutagenesis and a crystallographic inhibitor-binding study confirmed that the lysozyme-like domain contains the active site of SLT.

Binding Sites↗
PubMed1998

Anchor structure of staphylococcal surface proteins. II. Cooh-terminal structure of muramidase and amidase-solubilized surface protein.

Surface proteins of the Gram-positive organism Staphylococcus aureus are anchored to the bacterial cell wall by a transpeptidation mechanism during which the polypeptide is cleaved between the threonine (T) and the glycine (G) of the LPXTG motif. The carboxyl of threonine is subsequently amide linked to the amino of the pentaglycyl cross-bridge within the staphylococcal peptidoglycan. Previous work examined the anchor structure of surface proteins solubilized from the peptidoglycan by treatment with lysostaphin or phi11 hydrolase and identified COOH-terminally linked triglycyl or L-Ala-D-iGln-L-Lys(Gly5)-D-Ala and MurNAc-[L-Ala-D-iGln-L-Lys(Gly5)-D-Ala](beta1-4)-GlcNAc, respectively. Here, we report the anchor structure of surface proteins solubilized with N-acetylmuramidase and N-acetylmuramyl-L-alanine amidase. N-Acetylmuramidase-released surface protein was linked to MurNAc-[L-Ala-D-iGln-L-Lys(Gly5)-D-Ala](beta1-4)-GlcNAc, whereas N-acetylmuramyl-L-alanine amidase treatment of the cell wall solubilized surface proteins linked to L-Ala-D-iGln-L-Lys(Gly5)-D-Ala. Most, but not all, anchor structures were cross-linked to other cell wall subunits, in which the D-alanyl at position four was amide linked to the pentaglycyl of a neighboring wall peptide.

Amidohydrolases↗
PubMed1966

Serum and urinary lysozyme (muramidase) in monocytic and monomyelocytic leukemia.

Markedly increased quantities of lysozyme have been found in the serum and urine (ranging to 2.6 g per day) of ten consecutive cases of monocytic and monomyelocytic leukemia. The enzyme has been isolated from the urine of several cases and physicochemically and immunochemically characterized. It is apparently identical to the lysozyme of normal tears, saliva, leukocytes, and serum, but structurally different from the lysozyme of hen's egg white. The activity of the human enzyme assayed with M. lysodeikticus organisms is 3 to 12 times greater than egg white lysozyme at equivalent concentrations. An agar plate method has been developed for quantitating lysozyme activity in small samples (approximately 25 microl) of serum, urine, or other biological fluids. The range and reproducibility of this method were found to be superior to previously available lysozyme assay procedures. Present evidence indicates that lysozyme is the principal, if not the sole, product of the proliferating monocytes in monocytic and monomyelocytic leukemia, and quantitation of serum and urine lysozyme should be a useful diagnostic procedure for these leukemias.

Aged↗
PubMed1982

Lysozyme (muramidase) in pleural effusions and serum.

The authors evaluated the usefulness of paired pleural fluid and serum lysozyme determination in the differential diagnosis of pleurisies in 118 patients. Lysozyme activity of tuberculous effusions was found significantly higher (P less than 0.001) than that of effusions due to malignancy or heart failure, but considerable overlap of the individual values was observed. All patients with tuberculous pleurisy or tuberculous empyema, as well as a group of patients with suspected tuberculous effusion, had pleural fluid to serum lysozyme ratio of 1.0 or greater. In the remaining groups, only three patients, one with malignancy, one with lupus erythematosus, and one with sarcoidosis, exceeded this value. Their results suggest that pleural fluid to serum lysozyme ratio can be applied effectively in the differential diagnosis of tuberculous pleurisy.

Adult↗