Purification, characterization, and chemical modification of manganese peroxidase from Bjerkandera adusta UAMH 8258

Ten strains of Bjerkandera adusta from the University of Alberta Microfungus Collection and Herbarium (UAMH) were compared for manganese peroxidase production. The enzyme from B. adusta UAMH 8258 was chosen for further study. After purification the enzyme showed a molecular weight of 43 kDa on 15% SDS-PAGE, 36.6 kDa on matrix-assisted laser desorption ionization-time of flight mass spectrometry, and an isoelectric point of 3.55. The N-terminal amino acid sequence was determined to be VAXPDGVNTATNAAXXALFA, and the amino acid composition showed no tyrosine residues in the enzyme. Manganese peroxidase exhibited both Mn(II)-dependent (optimum pH 5) and Mn(II)-independent activity (optimum pH 3). The purified enzyme was chemically modified with cyanuric chloride-activated methoxypolyethylene glycol to enhance its surface hydrophobicity. The modified and native enzymes showed similar catalytic properties in the oxidation of Mn(II) and other substrates such as 2,6-dimethoxylphenol, veratryl alcohol, guaiacol, and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonate). However, the modified enzyme showed greater resistance to denaturation by hydrogen peroxide and stability to organic solvents such as acetonitrile, N,N-dimethylformamide, tetrahydrofuran, methanol, and ethanol. The PEG-modified enzyme also showed greater stability to higher temperatures and lower pH than the native enzyme. Thus, chemical modification of manganese peroxidase from B. adusta increases its potential usefulness for applied studies.