title: Aggregation and chemical reaction in hen lysozyme caused by heating at pH 6 are depressed by osmolytes, sucrose and trehalose.
abstract: We examined the effects of osmolytes, sucrose and trehalose, on the deterioration of hen lysozyme as a model protein. Sucrose and trehalose depressed the aggregation of lysozyme molecules caused by heating at 100 degrees C at pH 6. Since lysozyme was fully denatured under these conditions, the effects of sucrose and trehalose on the denatured state of lysozyme were investigated using reduced S-alkylated lysozyme, a model of denatured hen lysozyme. From analyses of circular dichroism spectra and fluorescence spectra, sucrose and trehalose were found to induce alpha-helical conformations and some tertiary structures around tryptophan residues in the reduced S-alkylated lysozyme. Moreover, these compounds also depressed chemical reactions such as deamidation and racemization, which often cause the deterioration of proteins, on the reduced S-alkylated lysozyme. Therefore, the data suggest that sucrose and trehalose have a propensity to depress such deterioration as the aggregation of protein molecules or chemical reactions in proteins by inducing some tertiary structures (including alpha-helical structures) in the polypeptide chain.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan. ueda@phar.kyushu-u.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Ueda
authors.forename: M
authors.initials: M
authors.lastname: Nagata
authors.forename: T
authors.initials: T
authors.lastname: Imoto
mesh_terms: D000478:Alkylation; D000818:Animals; D002942:Circular Dichroism; D004795:Enzyme Stability; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009113:Muramidase / Q000737:chemistry* / Q000187:drug effects; D009997:Osmotic Pressure; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013050:Spectrometry, Fluorescence; D013395:Sucrose / Q000494:pharmacology*; D014199:Trehalose / Q000494:pharmacology*; D014364:Tryptophan / Q000737:chemistry
chemical_list: D013395:Sucrose; D014364:Tryptophan; D014199:Trehalose; C421864:hen egg lysozyme; D009113:Muramidase