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

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E. V. Stepanova¹, T. V. Fedorova¹, O. N. Sorokina², V. V. Volkov³, O. V. Koroleva^1*, and A. T. Dembo^3#

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

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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.

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KEY WORDS: laccase, phase transitions, small angle X-ray scattering (SAXS), EPR spectra, active site

DOI: 10.1134/S0006297909040051

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