title: Preparation of antimicrobial reduced lysozyme compatible in food applications.
abstract: The structural and antimicrobial functions of lysozyme reduced with food-compatible reducing agents-cysteine (Cys) and glutathione (GSH)-were investigated. The disulfide bonds were partially reduced by thiol-disulfide exchange reactions under heat-induced denaturing conditions from 55 to 90 degrees C. The results showed that treatment of lysozyme with Cys and GSH resulted in the introduction of new half-cystine residues (2-3 residues/mol of protein). The released SH groups, in turn, rendered the lysozyme molecule more flexible, being accompanied by a dramatic increase in the surface hydrophobicity and exposure of tryptophan residues. As a consequence, the resulting reduced lysozymes were more capable of binding to lipopolysaccharides (LPS) and permeabilizing the bacterial outer membrane, as evidenced by the liposome leakage experiment, than were native or heated lysozyme. Both reduced lysozymes displayed significantly higher antimicrobial activity than native or heated lysozyme against Salmonella enteritidis (SE) in sodium phosphate buffer (10 mM, pH 7.2) at 30 degrees C for 1 h. Their minimal inhibitory concentrations (MICs) against the tested bacteria were about 150- and 25-fold lower than their respective MICs of native or heated lysozyme. The results suggest that partially reduced lysozyme could be used as a potential antimicrobial agent for prevention of SE attack.
authors.affiliation: Department of Biochemistry and Food Science, Faculty of Agriculture, Kagawa University, Ikenobe, Kagawa, Japan.
authors.forename: Visalsok
authors.initials: V
authors.lastname: Touch
authors.forename: Shigeru
authors.initials: S
authors.lastname: Hayakawa
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Fukada
authors.forename: Yuka
authors.initials: Y
authors.lastname: Aratani
authors.forename: Yuanxia
authors.initials: Y
authors.lastname: Sun
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D003545:Cysteine / Q000737:chemistry; D005503:Food Additives; D005978:Glutathione / Q000737:chemistry; D006358:Hot Temperature; D008070:Lipopolysaccharides / Q000378:metabolism; D009113:Muramidase / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D010084:Oxidation-Reduction; D012477:Salmonella enteritidis / Q000187:drug effects; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000737:chemistry
chemical_list: D000900:Anti-Bacterial Agents; D005503:Food Additives; D008070:Lipopolysaccharides; D014364:Tryptophan; D009113:Muramidase; D005978:Glutathione; D003545:Cysteine