title: Inhibition of lysozyme by taurine dibromamine.
abstract: Hypobromous acid (HOBr) is a powerful oxidant produced by stimulated neutrophils and eosinophils. Taurine, a non-protein amino acid present in high amounts in the leukocytes, reacts instantaneously with HOBr leading to their haloamine derivative taurine dibromamine (Tau-NBr2). Lysozyme is a bactericidal enzyme also present in leukocytes and in secretory fluids. The inhibition of lysozyme is a pathway for bacterial proliferation in inflammatory sites. Here, we investigated the inhibition of the enzymatic activity of lysozyme when it was submitted to oxidation by Tau-NBr2. We found that the oxidation of lysozyme by Tau-NBr2 decreased its enzymatic activity in 80%, which was significant higher compared to the effect of its precursor HOBr (30%). The study and comparison of Tau-NBr2 and HOBr regarding the alterations provoked in the intrinsic fluorescence, synchronous fluorescence, resonance light scattering and near and far-UV circular dichroism spectra of lysozyme and oxidized lysozyme revealed that tryptophan residues in the active site of the protein were the main target for Tau-NBr2 and could explain its efficacy as inhibitor of lysozyme enzymatic activity. This property of Tau-NBr2 may have pathological significance, since it can be easily produced in the inflammatory sites.
authors.affiliation: Department of Chemistry, Faculty of Science, São Paulo State University (UNESP), 17033-360, Bauru, São Paulo, Brazil. vfximenes@fc.unesp.br.
authors.forename: M S
authors.initials: MS
authors.lastname: Petrônio
authors.forename: V F
authors.initials: VF
authors.lastname: Ximenes
mesh_terms: D000818:Animals; D001959:Bromates / Q000737:chemistry; D049109:Cell Proliferation / Q000187:drug effects*; D002642:Chick Embryo / Q000201:enzymology*; D002942:Circular Dichroism; D004531:Eggs; D004804:Eosinophils / Q000737:chemistry / Q000378:metabolism; D008837:Micrococcus / Q000187:drug effects; D009113:Muramidase / Q000037:antagonists & inhibitors / Q000737:chemistry*; D009504:Neutrophils / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D013654:Taurine / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology*; D014364:Tryptophan / Q000737:chemistry
chemical_list: D001959:Bromates; D013654:Taurine; D014364:Tryptophan; D009113:Muramidase; C027664:hypobromous acid