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Investigations on the Determinants Responsible for Low Molar Mass Dextran Formation by DSR-M Dextransucrase

Claverie, Marion and Cioci, Gianluca and Vuillemin, Marlène and Monties, Nelly and Roblin, Pierre and Lippens, Guy and Remaud-Simeon, Magali and Moulis, Claire Investigations on the Determinants Responsible for Low Molar Mass Dextran Formation by DSR-M Dextransucrase. (2017) ACS Catalysis, 7 (10). 7106-7119. ISSN 2155-5435

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Official URL: https://doi.org/10.1021/acscatal.7b02182


Certain enzymes of the GH70 family dextransucrases synthesize very high molar mass dextran polymers, whereas others produce a mixed population of very high and low molar mass products directly from sucrose substrate. Identifying the determinants dictating polymer elongation would allow the tight control of dextran size. To explore this central question, we focus on the recently discovered DSR-M enzyme from Leuconostoc citreum NRRL B-1299, which is the sole enzyme that naturally, exclusively, and very efficiently produces only low molar mass dextrans from sucrose. Extensive biochemical and structural characterization of a truncated form of DSR-M (DSR-MΔ2, displaying the same biochemical behavior as the parental enzyme) and X-ray structural analysis of complexes with sucrose and isomaltotetraose molecules together with accurate monitoring of the resulting polymer formation reveal that DSR-MΔ2 adopts a nonprocessive mechanism attributed to (i) a high propensity to recognize sucrose as a preferred acceptor at the initial stage of catalysis, (ii) an ability to elongate oligodextrans irrespective of their size, and (iii) the presence of a domain V showing a weak ability to bind to the growing dextran chains. In this study, we present the 3D structure with the largest defined domain V reported to date in the GH70 family and map sugar binding pockets on the basis of the structure of the complex obtained with isomaltotetraose. Altogether, these findings give insights into the interplay between the domain V and the catalytic site during polymerization. They open promising strategies for GH70 enzyme engineering aiming at modulating glucan size.

Item Type:Article
HAL Id:hal-01886431
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
French research institutions > Institut National de la Recherche Agronomique - INRA (FRANCE)
Université de Toulouse > Institut National des Sciences Appliquées de Toulouse - INSA (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
Laboratory name:
French National Research Agency (ANR) - French Ministry of Higher Education
Deposited On:19 Oct 2018 09:01

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