title: The g-type lysozyme of Scophthalmus maximus has a broad substrate spectrum and is involved in the immune response against bacterial infection.
abstract: Lysozyme is a muramidase that inflicts damage on bacterial cell wall by catalyzing the cleavage of the beta-1,4-glycosidic bond between N-acetylmuramic acid and N-acetylglucosamine in peptidoglycan. Lysozymes are classified into several types, one of which is the goose-type (g-type). In this study, we identified and analyzed a g-type lysozyme (SmLysG) from turbot Scophthalmus maximus. The deduced amino acid sequence of SmLysG contains 193 residues and is most closely related to that of the g-type lysozyme of Scophthalmus rhombus (94% overall identity). SmLysG possesses a Goose Egg White Lysozyme (GEWL) domain with conserved residues essential for catalytic activity. Recombinant SmLysG (rSmLysG) purified from yeast exhibits strong lysozyme activity against Micrococcus luteus. Enzyme assays showed that the optimal temperature and pH of rSmLysG are 30°C and pH 7.0, respectively. Substrate spectrum analysis indicated that rSmLysG inhibited the growth of a number of important fish pathogens of both Gram-negative and Gram-positive natures. SmLysG transcription was detected in multiple tissues and was upregulated in kidney and spleen by experimental challenges with lipopolysaccharide and bacterial pathogens that are, respectively, sensitive to and resistant against the lytic effect of rSmLysG. Comparative analysis showed that although bacterial infection also induced the expression of c-type lysozyme, the induction levels were much lower than those of SmLysG. Taken together, these results indicate that SmLysG is a functional g-type lysozyme with a wide working range and is involved in innate immune defense against general bacterial infection.
authors.affiliation: Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao 266071, PR China.
authors.forename: Lu
authors.initials: L
authors.lastname: Zhao
authors.forename: Jin-Sheng
authors.initials: JS
authors.lastname: Sun
authors.forename: Li
authors.initials: L
authors.lastname: Sun
mesh_terms: D000818:Animals; D001419:Bacteria / Q000276:immunology; D001424:Bacterial Infections / Q000276:immunology / Q000662:veterinary*; D005393:Fish Diseases / Q000276:immunology*; D005412:Flatfishes / Q000235:genetics* / Q000276:immunology*; D020869:Gene Expression Profiling; D015971:Gene Expression Regulation, Enzymologic; D006863:Hydrogen-Ion Concentration; D007107:Immune System / Q000201:enzymology*; D008969:Molecular Sequence Data; D009113:Muramidase / Q000737:chemistry / Q000235:genetics* / Q000276:immunology*; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification; D016415:Sequence Alignment; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D011994:Recombinant Proteins; D009113:Muramidase