title: Enhancement of hydrogen peroxide stability of a novel Anabaena sp. DyP-type peroxidase by site-directed mutagenesis of methionine residues.
abstract: Previous reports have shown that a unique bacterial dye-decolorizing peroxidase from the cyanobacterium Anabaena sp. strain PCC7120 (AnaPX) efficiently oxidizes both recalcitrant anthraquinone dyes (AQ) and typical aromatic peroxidase substrates. In this study, site-directed mutagenesis to replace five Met residues in AnaPX with high redox residues Ile, Leu, or Phe was performed for the improvement of the enzyme stability toward H(2)O(2). The heme cavity mutants M401L, M401I, M401F, and M451I had significantly increased H(2)O(2) stabilities of 2.4-, 3.7-, 8.2-, and 5.2-fold, respectively. Surprisingly, the M401F and M451I retained 16% and 5% activity at 100 mM H(2)O(2), respectively, in addition to maintaining high dye-decolorization activity toward AQ and azo dyes at 5 mM H(2)O(2) and showing a slower rate of heme degradation than the wildtype enzyme. The observed stabilization of AnaPX may be attributed to the replacement of potentially oxidizable Met residues either increasing the local stability of the heme pocket or limiting of the self-inactivation electron transfer pathways due to the above mutations. The increased stability of AnaPX variants coupled with the broad substrate specificity can be potentially useful for the further practical application of these enzymes especially in bioremediation of wastewater contaminated with recalcitrant AQ.
authors.affiliation: Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504, Japan.
authors.forename: Henry Joseph Oduor
authors.initials: HJ
authors.lastname: Ogola
authors.forename: Naoya
authors.initials: N
authors.lastname: Hashimoto
authors.forename: Suguru
authors.initials: S
authors.lastname: Miyabe
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ashida
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Shibata
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Sawa
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics*; D017033:Anabaena / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004795:Enzyme Stability; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008715:Methionine / Q000235:genetics*; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009195:Peroxidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D050505:Mutant Proteins; D008715:Methionine; D006861:Hydrogen Peroxide; D009195:Peroxidase