Sep 15, 2010

Xylanase II from Trichoderma reesei QM 9414: conformational and catalytic stability to Chaotropes, Trifluoroethanol, and pH changes

Journal of Industrial Microbiology & Biotechnology
Gloria LópezP Estrada


Xylanase II, a key enzyme in the hydrolysis of xylan, was purified from cultures of Trichoderma reesei QM 9414 (anamorph of Hypocrea jecorina) grown on wheat straw as a carbon source. Xylanase treated with increasing guanidinium hydrochloride concentrations was denatured in a cooperative way regarding secondary and tertiary structures with midpoint transitions 5.6 ± 0.1 and 3.7 ± 0.1 M, respectively, whereas the enzymatic activity showed an intermediate state at 2-4 M denaturant. Treatment with urea showed that xylanase secondary structure was stabilized up to 4 M urea to be destabilized thereafter in a cooperative way with a transition midpoint Dm = 5.7 ± 0.2 M, but the ellipticity at 220 nm was greater than control in the presence of urea up to 6 M. Tertiary structure in the presence of urea showed also intermediate states with partial cooperative transitions with a midpoint: Dm = 2.7 ± 0.04 and 6.7 ± 0.3 M, respectively, whereas the enzymatic activity was enhanced about 40% at 2 M and inhibited above 4 M urea. Assays with the fluorescent probe 4,4'-bis-1-phenylamine-8-naphftalene sulfonate (bis-ANS) proved that the intermediate states had the characteristics of molten globule structures. The change of free energy for xylanas...Continue Reading

Mentioned in this Paper

Molecular Helix
Guanidine Sulfite (1: 1)
Tertiary Protein Structure
Helix (Snails)
Xylanase Activity
Trichoderma reesei
Xylan Endo-1,3-beta-Xylosidase

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