Domain structure of laccase I from the lignin-degrading basidiomycete PM1 revealed by differential scanning calorimetry.

The application of scanning calorimetry to investigate laccase I from the lignin-degrading basidomycete PM1 (CECT 2971) showed three thermal transitions beneath the overall endotherm following the previous heating of the sample up to 60 degrees C. The thermodynamic parameters of these three transitions satisfy a model of two-state independent unfolding, supporting a three-domain organization of the enzyme. It is shown that the catalytic site of laccase I is located in the domain with the thermally-induced transition at 76 degrees C.