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Effect of Solvent Phase Transitions on Enzymatic Activity and Structure of Laccase from Coriolus hirsutus

E. V. Stepanova1, T. V. Fedorova1, O. N. Sorokina2, V. V. Volkov3, O. V. Koroleva1*, and A. T. Dembo3#

1Bach Institute of Biochemistry, Russian Academy of Sciences, Leninsky pr. 33, 119071 Moscow, Russia; fax: (495) 954-2732; E-mail: koroleva@inbi.ras.ru

2Emmanuel Institute of Biochemical Physics, Russian Academy of Sciences, ul. Kosygina 4, 119334 Moscow, Russia; fax: (495) 137-4101; E-mail: alsiona1983@mail.ru

3Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninsky pr. 59, 119333 Moscow, Russia; fax: (495) 135-1011; E-mail: vvo@ns.crys.ras.ru

# Deceased.

* To whom correspondence should be addressed.

Received July 30, 2008; Revision received September 15, 2008
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°C was shown. Spontaneous oxidation of T1 copper center in the temperature range 12-20°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.
KEY WORDS: laccase, phase transitions, small angle X-ray scattering (SAXS), EPR spectra, active site

DOI: 10.1134/S0006297909040051