Structural determinants of product specificity of sucrose isomerases

Ravaud, Stéphanie; Robert, Xavier; Watzlawick, Hildegard; Haser, Richard; Mattes, Ralf; Aghajari, Nushin

doi:10.1016/j.febslet.2009.05.002

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Volume 583, Issue 12 , Pages 1964-1968, 18 June 2009

Structural determinants of product specificity of sucrose isomerases

Edited by Hans Eklund

Stéphanie Ravaud
- Laboratoire de BioCristallographie, Institut de Biologie et Chimie des Protéines, UMR 5086-CNRS/Université de Lyon, IFR128 “BioSciences Gerland – Lyon Sud”, 7 Passage du Vercors, F-69367 Lyon cedex 07, France
- Present address: Institut de Biologie Structurale Jean-Pierre Ebel, UMR 5075 CEA-CNRS-Université Joseph Fourier, F-38027 Grenoble cedex 1, France.
Xavier Robert
- Laboratoire de BioCristallographie, Institut de Biologie et Chimie des Protéines, UMR 5086-CNRS/Université de Lyon, IFR128 “BioSciences Gerland – Lyon Sud”, 7 Passage du Vercors, F-69367 Lyon cedex 07, France
Hildegard Watzlawick
- Universität Stuttgart, Institut für Industrielle Genetik, Allmandring 31, D-70569 Stuttgart, Germany
Richard Haser
- Laboratoire de BioCristallographie, Institut de Biologie et Chimie des Protéines, UMR 5086-CNRS/Université de Lyon, IFR128 “BioSciences Gerland – Lyon Sud”, 7 Passage du Vercors, F-69367 Lyon cedex 07, France
Ralf Mattes
- Universität Stuttgart, Institut für Industrielle Genetik, Allmandring 31, D-70569 Stuttgart, Germany
Nushin Aghajari
- Laboratoire de BioCristallographie, Institut de Biologie et Chimie des Protéines, UMR 5086-CNRS/Université de Lyon, IFR128 “BioSciences Gerland – Lyon Sud”, 7 Passage du Vercors, F-69367 Lyon cedex 07, France
- Corresponding author. Fax: +33 (0)472722616.

Received 21 April 2009; accepted 2 May 2009. published online 08 May 2009.

Abstract

The healthy sweetener isomaltulose is industrially produced from the conversion of sucrose by the sucrose isomerase SmuA from Protaminobacter rubrum. Crystal structures of SmuA in native and deoxynojirimycin complexed forms completed with modeling studies unravel the characteristics of the isomaltulose synthases catalytic pocket and their substrate binding mode. Comparison with the trehalulose synthase MutB highlights the role of Arg²⁹⁸ and Arg³⁰⁶ active site residues and surface charges in controlling product specificity of sucrose isomerases (isomaltulose versus trehalulose). The results provide a rationale for the specific design of optimized enzymes.

Keywords: Sucrose isomerase, Glycoside hydrolase, Aromatic clamp, Crystal structure, Deoxynojirimycin, Molecular modeling