title: [Catalytic properties of extracellular phenol oxidases from the higher basidiomycete Pleurotus ostreatus (Fr.) Kumm].
abstract: Phenol oxidase preparations possessing high stability in the reaction of phenols oxidation are isolated from the culture filtrates of four strains of higher basidiomycete Pleurotus ostreatus (F r.) Kumm. The preparations are able to oxidize mono- and diphenols with different substituents in o-, m- and p-positions to phenol hydroxyls as well as o- and p-phenylene diamines. A change in the orientation of substituents in the substrate molecule is followed by a change in the mechanism of its oxidation. The enzyme activity is determined by the type of substituents in the phenol molecule: electron-withdrawing groups impede and electron-releasing ones facilitate the substrate oxidation. The Hammett equation is shown to be applicable for description of monophenol oxidation. An explanation of high values of positive deviations from it in the case of halogen-substituted phenols is suggested. A conclusion is drawn that Km of enzymes for oxygen determined from the full kinetic curves of O2 uptake with phenol redundancy are kinetic constants depending on the substrate structure.
mesh_terms: D001487:Basidiomycota / Q000201:enzymology*; D002384:Catalysis; D004156:Catechol Oxidase / Q000378:metabolism*; D007700:Kinetics; D014442:Monophenol Monooxygenase / Q000302:isolation & purification / Q000378:metabolism*; D010084:Oxidation-Reduction; D011124:Polyporaceae / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D004156:Catechol Oxidase; D014442:Monophenol Monooxygenase
vernacular_title: Kataliticheskie svoĭstva vnekletochnykh fenoloksidaz vysshego bazidiomitseta Pleurotus ostreatus (Fr.) Kumm.