Kinetic differences of purified laccases from six Pleurotus ostreatus strains

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Abstract
Aims: Enzyme kinetics of purified laccases from six different Pleurotus ostreatus strains were determined in the oxidation of syringaldazine, guaiacol and ABTS. Methods and Results: Significant differences in the kinetic constants were found. Catalytic activity (kcat) ranged from 19 to 941 U mg−1 for syringaldazine, from 18 to 1565 U mg−1 for ABTS, and from 4 to 44 U mg−1 for guaiacol. The apparent affinity constants (KM) also showed significant differences between the different strains, from 12 to 52 μmol l−1 for syringaldazine, from 8 to 79 μmol l−1 for ABTS, and from 0·46 to 6·61 mmol l−1 for guaiacol. No differences were found either on the effect of increasing concentrations of organic solvent (acetonitrile) or on the activity pH profile. The temperature profile was the same for all the P. ostreatus strains, except for the IE8 strain, which seems to be more sensitive to temperature. The kinetic and stability data from the six P. ostreatus strains were also compared with those obtained from other white rot fungi, Coriolopsis gallica and Trametes versicolor, showing clear differences. Conclusions: The different P. ostreatus isolates showed different kinetic constants. Significance and Impact of the Study: The different enzymatic properties of laccases from various P. ostreatus strains should be considered for a potential industrial or environmental application.