| Abstrakt: |
Laccases of the basidiomycetes Cerrena unicolor 059, C. unicolor 0784, and Pleurotus oastreatus 0432 were subjected to a comparative study. The enzymes were isolated as homogeneous preparations with molecular weights of 55, 56, and 57 kD, respectively. The three enzymes were found to be glycoproteins. The carbohydrate moiety of the glycoproteins included mannose, galactose, and N-acetylglucosamine. The carbohydrate moieties of the laccases from C. unicolor 059, C. unicolor 0784, and P. oastreatus 0432 accounted for 17, 23, and 24%, respectively. The pH optima of the enzymes corresponded to 4.0, 3.75, and 5.6, respectively. Thermal stability tests (carried out at 40°C) demonstrated that the laccase of C. unicolor 0784 was characterized by the highest temperature resistance (the enzyme retained 25% activity after 172 h of incubation). The values of the Michaelis constant (KM) were determined for the reactions of oxidation of pyrocatechol, hydroquinone, and potassium ferrocyanide catalyzed by the laccases of the basidiomycetes. [ABSTRACT FROM AUTHOR] |
