Effect of Temperature on Xylanase II from Trichoderma reesei QM 9414: A Calorimetric, Catalytic, and Conformational Study
Figure 2
Fluorescence emission and catalytic behaviour of xylanase. (a) Fluorescence intensity emission spectrum of 0.09 mg·mL−1 xylanase in arbitrary units (a.u.) recorded at 20°C upon excitation at 275 nm (solid line), normalized trp residues emission (dotted line), and tyr residues emission (dashed line). Inset: detail of tyr residues emission at low wavelength. (b) Emission spectra of 0.09 mg·mL−1 xylanase recorded from 19°C to 70°C upon excitation at 290 nm. IP means isofluorescent point. Inset: dependence of maximum emission wavelength on temperature. (c) Variation of the xylanase SCM with temperature. The line is a fit of data above 48°C to (1). Inset: normalized xylanase to NATA fluorescence emission ratio versus temperature. (d) Percent residual activity measured in standard conditions (55°C) of 1.3 μg xylanase after being preincubated for 30 min at the indicated temperatures. Data obtained at 45–65°C were fitted (solid line) to (1).
