Effect of solvent phase transitions on enzymatic activity and structure of laccase from Coriolus hirsutus.

The effect of solvent phase transitions on catalytic activity and structure of the active site of laccase produced by the Basidiomycetes Coriolus hirsutus 072 was studied. As shown by small-angle X-ray scattering, laccase exists in solution as a mixture of monomeric and aggregated particles in the percent ratio 85:15. This ratio did not change on phase transitions. A complex nature of laccase activity dynamics during thawing and further heating to 20 degrees C was shown. Spontaneous oxidation of T1 copper center in the temperature range 12-20 degrees C was not observed. According to spectral data, the structure of laccase active sites including all copper centers of types T1, T2, and T3 changes during the phase transition.