title: Purification and characteristics of an enzyme with both bilirubin oxidase and laccase activities from mycelium of the basidiomycete Pleurotus ostreatus.
abstract: A homogenous enzyme with both bilirubin oxidase and laccase activities was isolated from a submerged culture of the basidiomycete Pleurotus ostreatus mycelium and characterized. The yield of the enzyme was 127 microg/g dry biomass of the mycelium. The specific activity of the enzyme was 21 and 261 U/mg to bilirubin and to a laccase substrate ABTS, respectively. The intracellular phenol oxidase from the P. ostreatus mycelium was identified as bilirubin oxidase with the amino acid sequence highly homologous to that of the pox2 gene-encoded product. The enzyme displayed the maximal laccase activity at 50-55 degrees C to all substrates examined, whereas the pH optimum was substrate-dependent and changed from 3.0 for ABTS to 7.0 for syringaldazine and guaiacol. The enzyme maintained catalytic activity within a broad pH range but was inactivated at pH 4.0. The enzyme was thermostable but very sensitive to metal chelating inhibitors. Trypan Blue (5 mg/liter) was completely decolorizated upon 3 h of incubation with the bilirubin oxidase (20 mU/ml) at room temperature.
authors.affiliation: Sakharov International Environmental University, Minsk, 220009, Belarus. pohodnia@yahoo.com
authors.forename: Y G
authors.initials: YG
authors.lastname: Pakhadnia
authors.forename: N I
authors.initials: NI
authors.lastname: Malinouski
authors.forename: A G
authors.initials: AG
authors.lastname: Lapko
mesh_terms: D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D042845:Laccase / Q000302:isolation & purification* / Q000378:metabolism; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000302:isolation & purification* / Q000378:metabolism; D020076:Pleurotus / Q000201:enzymology* / Q000254:growth & development; D021241:Spectrometry, Mass, Electrospray Ionization; D013379:Substrate Specificity; D053719:Tandem Mass Spectrometry
chemical_list: D042845:Laccase; D044925:Oxidoreductases Acting on CH-CH Group Donors; C042401:bilirubin oxidase