Comparison of physico-chemical characteristics of four laccases from different basidiomycetes

New strains of basidiomycetes producing extracellular laccases (Trametes ochracea 92-78, and Trametes hirsuta 56) have been found by screening of isolates of Trametes fungi. The laccases from T. hirsuta 56 and T. ochracea 92-78 as well as two laccases from previously found and described strains of basidiomycetes, namely Cerrena maxima and Coriolopsis fulvocinerea, were purified to homogeneity. The standard redox potentials of type 1 copper in the enzymes were determined and found to be 780, 790, 750, and 780 mV, respectively. The spectral and biochemical studies showed that the enzymes had no significant differences between the structures of their active sites (T1, T2, and T3). In spite of this fact, the basic biochemical properties as well as the redox potentials of the T 1 sites of the enzymes were found to be different. The molecular weights of the laccases range from 64 to 70 kDa, and their pl values range from 3.5 to 4.7. The pH-optima are in the range 3.5-5.2. The temperature optimum for activity is about 50 C. The thermal stabilities of the enzymes were studied. The catalytic and Michaelis constants for catechol, guaiacol, hydroquinone, sinapinic acid, and K4Fe(CN)(6) were determined. Based on these results as well as results obtained by comparing with published properties of several laccases, it could be concluded that T. hirsuta and Cerrena maxima laccases have some superior characteristics such as high stability, high activity, and low carbohydrate content, making them attractive objects for further investigations as well as for application in different areas of biotechnology. (C) 2004 Elsevier SAS. All rights reserved.