Structural and biochemical data of Trichoderma harzianum GH1 β-glucosidases

1Data

Three sets of data are shown. First, the statistics and parameters from the X-ray diffraction data processing and structural refinement are given for the crystal structures of the enzymes ThBgl1 and ThBgl2. Second, the preferences for different natural and synthetic substrates are shown for these enzymes and, finally, the influence of pH and temperature on the enzyme activity is provided.

2Experimental design, materials and methods

The complete description of the methods is found in the associated research article [1]. For the determination of optimum pH and temperatures for enzyme activity, a reaction mixture using the synthetic substrate 4-nitrophenyl-β-D-glucopyranoside (pNPG Fig. 1). Briefly, 50 μL of pNPG (final concentration of 5 mM), 40 μL of 150 mM citrate-phosphate or phosphate buffer at different pHs and 10 μL of enzyme at 0.1 mg/ml were incubated for 5, 10, 15 and 20 minutes at 30 °C. The reaction was stopped by adding 100 μL of Na₂CO₃ 0.5 M and the amount of released products was measured spectrophometrically at 415 nm. For the determination of optimum temperature, the same reactions were incubated in a temperature range spanning 20 to 70 °C in 5 °C steps (Fig. 2). After 10 minutes, the reaction was stopped by adding 100 μL of Na₂CO₃ 1 M and the amount of released products was measured spectrophometrically at 405 nm.

The substrate preferences for ThBgl1 and ThBgl2 were evaluated using different synthetic substrates: pNPG, 4-nitrophenyl-β-D-xylopyranoside (pPNX), 4-nitrophenyl-α-D-galactopyranoside (pNPGal), 2-nitrophenyl-β-D-galactopyranoside, 4-nitrophenyl-β-D-cellobioside and 4-nitrophenyl-β-D-mannopyranoside (pNPM). All the reactions were tested at 35 °C for ThBgl1 and 40 °C for ThBgl2, using sodium phosphate buffer pH 5.5.

Purified ThBgl1 and ThBgl2 were used for crystallization trials at 25 mg/ml 30 mg/ml, respectively. For ThBgl1 crystals grew in 0.2 M hexahydrated magnesium chloride, 0.1 M HEPES pH 7.5 and 25% PEG3350. For ThBgl2, suitable crystals grew in a solution containing 0.1 MES pH 6.5, 25% PEG 8000. The crystals were flash frozen in a nitrogen stream under 100 K and used for data collection. For ThBgl1 crystal a complete dataset was collected in the MX-2 beamline of the Brazilian Synchrotron Light Source [2]. For ThBgl2 a complete dataset was collected using a Bruker APEX-Duo home source using copper Kα radiation. The scattered intensities were integrated using iMosflm [3] and, after scaling with AIMLESS [4], the structure factors were used for phasing by molecular replacement using the crystal structure of T. reesei GH1 β-glucosidase as the search model [5] and PHASER [6] software. Finally, the crystal structures were refined in iterative cycle of real space manual refinement using Coot [7] and reciprocal space refinement using PHENIX [8] software (Table 1).

Fig. 1

Influence of pH on ThBgl1 (A) and ThBgl2 (B) activities in pNPG.

Fig. 1:

Fig. 2

Temperature influence on ThBgl1 (a) and ThBgl2 (b) activities measured in pNPG.

Fig. 2: