title: Effect of protein concentration and pH on the chitinase activity of Tapes japonica lysozyme.
abstract: Tapes japonica lysozyme (TJL), which belongs to the invertebrate-type lysozyme family, has a unique dimer formation. The residues, which include catalytic residues (glutamate 18 and aspartate 30), at the dimer interface form electrostatic interactions. Our previous study suggested that increasing the NaCl concentration switched TJL from a dimer to monomer structure, which increased TJL activity. Therefore, conversion from the dimeric to the monomeric structure is crucial for the TJL activity. In the present study, to further understand the effect of NaCl on TJL dimer formation, we examined the protein concentration and pH dependence of TJL activity in the presence or absence of 500 mM NaCl. TJL activity was suppressed at the high protein concentration. And the optimum pH of TJL activity was decreased in the absence of NaCl. These dependencies confirm the presence of electrostatic interactions between molecules of TJL in the dimeric form in an aqueous solution.
authors.affiliation: Graduate School of Pharmaceutical Sciences of Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Goto
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Abe
authors.forename: Taiji
authors.initials: T
authors.lastname: Imoto
authors.forename: Tadashi
authors.initials: T
authors.lastname: Ueda
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D049872:Bivalvia / Q000201:enzymology*; D002686:Chitin / Q000378:metabolism*; D005960:Glucosides / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D009113:Muramidase / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D009844:Oligosaccharides / Q000378:metabolism; D009994:Osmolar Concentration; D055503:Protein Multimerization; D012462:Saline Solution, Hypertonic / Q000737:chemistry; D012984:Software; D013379:Substrate Specificity
chemical_list: D000596:Amino Acids; D005960:Glucosides; D009844:Oligosaccharides; D012462:Saline Solution, Hypertonic; C055288:4-nitrophenyl-N,N',N'',N''',N''''-pentaacetyl-beta-chitopentaoside; D002686:Chitin; D009113:Muramidase