Lysozyme properties

Lysozyme is an enzyme that hydrolyzes polysaccharide chains. It ruptures certain bacterial cells by cleaving the polysaccharide chains that make up their cell wall. Lysozyme is found in many body fluids, but the most thoroughly studied form is from hen egg whites. The Russian scientist P. Laschtchenko first described the bacteriolytic properties of hen egg white lysozyme in 1909. In 1922, Alexander Fleming, the London bacteriologist who later discovered penicillin, gave the name lysozyme to the agent in mucus and tears that destroyed certain bacteria, because it was an enzyme that caused bacterial lysis. 

Just as individual amino acids have isoelectric points, proteins have an overall p/ because of the acidic or basic amino acids they may contain. The enzyme lysozyme, for instance, has a preponderance of basic amino acids and thus has a high isoelectric point (p/= 11.0). Pepsin, however, has a preponderance of acidic amino acids and a low- isoelectric point pi 1.0). Not surprisingly, the solubilities and properties of proteins with different pi s are strongly affected by the pH of the medium. Solubility- is usually lowest at the isoelectric point, where the protein has no net charge, and is higher both above and below the pi, where the protein is charged. 

Finally, we come to enzyme models. D. W. Griffiths and M. L. Bender describe the remarkable catalytic property of certain cycloamyloses which act through formation of inclusion complexes, and in this respect recall the clefts containing the active sites in enzymes such as lysozyme and papain. 

Habeeb, A.F.S.A., and Atassi, M.Z. (1970) Enzymatic and immunochemical properties of lysozyme. Evaluation of several amino group reversible blocking reagents. Biochemistry 9, 4959—4944. 

The model systems, discussed here, contain one type of well-defined protein and one type of well-characterized solid surface in an aqueous medium containing one type of low molecular-weight electrolyte. Table 2 summarizes some relevant properties of the proteins. Lysozyme (LSZ)... 

Some unnatural amino acids have been designed with this metal-chelating property in mind. For instance, bipyridylalanine (BpyAla, 27) has the bipyridyl group that chelates most transition metal ions and has been successfully incorporated into proteins in E. coli BpyAla was shown to reversibly bind copper ions when incorporated into T4 lysozyme, but a tyrosine in the same location was unable to bind copper, indicating that BpyAla is useful to coordinate copper ions to a protein of interest. 

If aspartic acid-52 acts as a nucleophile in lysozyme reactions a glycosyl enzyme intermediate will be formed [60]. There is no evidence, kinetic or otherwise, for substituted enzyme intermediates, but rapid breakdown might preclude attainment of detectable concentrations. Formation of a substituted enzyme could explain the observed retention of configuration at the anomeric carbon in transglycosidation reactions, provided backside attack in a subsequent reaction is chemically reasonable. It has therefore been important to attempt to understand the chemistry of acylal hydrolysis so as to assess the properties that would be expected of an acylal intermediate in reactions catalysed by the enzyme. 

Exposure of animals to ozone lowers their resistance to bacterial infection of the limgs ( ). Ozone exposure also causes changes in the properties of material that can be lavaged from the lungs there is inactivation of the enzymes acid phosphatase, 3-glucuronidase and lysozyme, and there is a tendency for these enzymes to have been released from the alveolar macrophage cells ( ). vivo inactivation of lung lysozyme has... 

In order to analyse the properties of the inactivated lysozyme, the enzyme was subjected to further analysis by electrophoresis and chromatography. Both analyses of the samples at various pHs, inactivated to the extent over 95%, indicated that the product is composed of one peak. The ozonized lysoz3mie moved slower than the native lysozyme on DEAE-Sephadex and the products at different pHs were readily distinguished from each other (Fig, 3), However, a diffuse band was observed for ozonized lysozyme as distinct from a sharp band for native lysozyme in polyacrylamide gel (17), The presence of only one band suggests that the ozonolysis does not cause the cleavage of peptide bonds and the remaining activity is not due to the presence of a small amount of unmodified lysozyme. 

Distinct changes in several properties of lysozyme occur after reaction with ozone. The lytic activity of the ozonized lysozyme shows the same trend at various pHs as the native enz3mie (Fig. 2) this may suggest that the pK values of the ionizable groups involved in catalysis have not been altered by ozonplysis. The amino acid composition of ozonized lysozyme differs from that of the native enz3mie in three residues — methionine, tryptophan and t3H osine. None of the other amino acids is affected by ozone. The extensive loss of enz5miic activity must be ascribed to the oxidative modification of these three amino acid residues in the lysozyme. 

Habeeb, A. F. S. A. and Atassi, M. Z. 1971. Enzymic and immunochemical properties of lysozyme. IV. Demonstration of conformational differences between a-lactal-bumin and lysozyme. Biochim. Biophys. Acta 236, 131-141. 

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