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

Abstract

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

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

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