Document Detail

Identification of critical residues for the activity and thermostability of Streptomyces sp. SK glucose isomerase.
MedLine Citation:
PMID:  23463249     Owner:  NLM     Status:  Publisher    
The role of residue 219 in the physicochemical properties of D-glucose isomerase from Streptomyces sp. SK strain (SKGI) was investigated by site-directed mutagenesis and structural studies. Mutants G219A, G219N, and G219F were generated and characterized. Comparative studies of their physicochemical properties with those of the wild-type enzyme highlighted that mutant G219A displayed increased specific activity and thermal stability compared to that of the wild-type enzyme, while for G219N and G219F, these properties were considerably decreased. A double mutant, SKGI F53L/G219A, displayed a higher optimal temperature and a higher catalytic efficiency than both the G219A mutant and the wild-type enzyme and showed a half-life time of about 150 min at 85 °C as compared to 50 min for wild-type SKGI. Crystal structures of SKGI wild-type and G219A enzymes were solved to 1.73 and 2.15 Å, respectively, and showed that the polypeptide chain folds into two structural domains. The larger domain consists of a (β/α)8 unit, and the smaller domain forms a loop of α helices. Detailed analyses of the three-dimensional structures highlighted minor but important changes in the active site region as compared to that of the wild-type enzyme leading to a displacement of both metal ions, and in particular that in site M2. The structural analyses moreover revealed how the substitution of G219 by an alanine plays a crucial role in improving the thermostability of the mutant enzyme.
Hajer Ben Hlima; Samir Bejar; Jonas Riguet; Richard Haser; Nushin Aghajari
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-3-6
Journal Detail:
Title:  Applied microbiology and biotechnology     Volume:  -     ISSN:  1432-0614     ISO Abbreviation:  Appl. Microbiol. Biotechnol.     Publication Date:  2013 Mar 
Date Detail:
Created Date:  2013-3-6     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8406612     Medline TA:  Appl Microbiol Biotechnol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Laboratoire de Micro-organismes et de Biomolécules, Centre de Biotechnologie de Sfax, Université de Sfax, BP "1177", 3018, Sfax, Tunisia.
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