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Directed Divergent Evolution of a Thermostable D-Tagatose Epimerase towards Improved Activity for Two Hexose Substrates

Bosshart, Andreas and Hee, Chee Seng and Bechtold, Matthias and Schirmer, Tilman and Panke, Sven. (2015) Directed Divergent Evolution of a Thermostable D-Tagatose Epimerase towards Improved Activity for Two Hexose Substrates. ChemBioChem, 16 (4). pp. 592-601.

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Official URL: http://edoc.unibas.ch/dok/A6411072

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Abstract

Functional promiscuity of enzymes can often be harnessed as the starting point for the directed evolution of novel biocatalysts. Here we describe the divergent morphing of an engineered thermostable variant (Var8) of a promiscuous D-tagatose epimerase (DTE) into two efficient catalysts for the C3 epimerization of D-fructose to D-psicose and of L-sorbose to L-tagatose. Iterative single-site randomization and screening of 48 residues in the first and second shells around the substrate-binding site of Var8 yielded the eight-site mutant IDF8 (ninefold improved kcat for the epimerization of D-fructose) and the six-site mutant ILS6 (14-fold improved epimerization of L-sorbose), compared to Var8. Structure analysis of IDF8 revealed a charged patch at the entrance of its active site; this presumably facilitates entry of the polar substrate. The improvement in catalytic activity of variant ILS6 is thought to relate to subtle changes in the hydration of the bound substrate. The structures can now be used to select additional sites for further directed evolution of the ketohexose epimerase.
Faculties and Departments:05 Faculty of Science > Departement Biozentrum
05 Faculty of Science > Departement Biozentrum > Structural Biology & Biophysics
05 Faculty of Science > Departement Biozentrum > Structural Biology & Biophysics > Structural Biology (Schirmer)
UniBasel Contributors:Schirmer, Tilman
Item Type:Article, refereed
Article Subtype:Research Article
Bibsysno:Link to catalogue
Publisher:Wiley-VCH
ISSN:1439-4227
e-ISSN:1439-7633
Note:Publication type according to Uni Basel Research Database: Journal article
Language:English
Identification Number:
Last Modified:10 Nov 2016 10:36
Deposited On:04 Sep 2015 14:30

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