Purification and characterization of two beta-glucosidases from the thermophilic fungus Thermoascus aurantiacus |
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Authors: | de Palma-Fernandez E R Gomes E da Silva R |
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Institution: | Centro Universitário de Rio Preto, S?o Paulo, Brazil. |
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Abstract: | β-Glucosidase from the fungusThermoascus aurantiacus grown on semi-solid fermentation medium (using ground corncob as substrate) was partially purified in 5 steps—ultrafiltration,
ethanol precipitation, gel filtration and 2 anion exchange chromatography runs, and characterized. After the first anion exchange
chromatography, β-glucosidase activity was eluted in 3 peaks (Gl-1, Gl-2, Gl-3). Only the Gl-2 and Gl-3 fractions were adsorbed
on the gel matrix. Gl-2 and Gl-3 exhibited optimum pH at 4.5 and 4.0, respectively. The temperature optimum of both glucosidases
was at 75–80°C. The pH stability of Gl-2 (4.0–9.0) was higher than Gl-3 (5.5–8.5); both enzyme activities showed similar patterns
of thermostability. Under conditions of denaturing gel chromatography the molar mass of Gl-2 and Gl-3 was 175 and 157 kDa,
respectively. Using 4-nitrophenyl β-d-glucopyranoside as substrate,K
m values of 1.17±0.35 and 1.38±0.86 mmol/L were determined for Gl-2 and Gl-3, respectively. Both enzymes were inhibited by
Ag+ and stimulated by Ca2+. |
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