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J Biotechnol. 2001 Jun 1;88(1):37-46.

A combination of weakly stabilizing mutations with a disulfide bridge in the alpha-helix region of Trichoderma reesei endo-1,4-beta-xylanase II increases the thermal stability through synergism.

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1
Laboratory of Bioprocess Engineering, Helsinki University of Technology, P.O. Box 6100, 02015-, HUT, Finland. ossi.turunen@hut.fi

Abstract

Thermal stability and other functional properties of Trichoderma reesei endo-1,4-beta-xylanase II (XYNII; family 11) were studied by designed mutations. Mutations at three positions were introduced to the XYNII mutant containing a disulfide bridge (S110C-N154C) in the alpha-helix. The disulfide bridge increased the half-life of XYNII from less than 1 min to 14 min at 65 degrees C. An additional mutation at the C-terminus of the alpha-helix (Q162H or Q162Y) increased the half-life to 63 min. Mutations Q162H and Q162Y alone had a stabilizing effect at 55 degrees C but not at 65 degrees C. The mutations N11D and N38E increased the half-life to about 100 min. Due to the stabilizing mutations the pH stability increased in a wide pH range, but at the same time the activity decreased both in acidic and neutral-alkaline pH, the pH optimum being at pH region 5-6. There was no essential difference between the specific activities of the mutants and the wild-type XYNII.

PMID:
11377763
[Indexed for MEDLINE]

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