SEMINAR

A bacterial beta-glucosidase serves as a model for human genetic disease

Abstract
Of these carbohydrate-active enzymes, beta-glucosidases (E.C. 3.2.1.21), which cut the glycosidic bonds at nonreducing terminal beta-glucosyl moieties (perhaps the most common sugar residues in nature), are of interest for their diverse specificities and possible applications. Glycoside hydrolase family 116 (GH116) is a recently described family of enzymes with beta-glucosidase activity, including human GBA2 glucosyl cerebrosidase and similar plant and bacterial proteins. In order to provide a structural model for this family, we have characterized and solved the structure of a bacterial representative of GH116, Thermoanaerobacterium xylanolyticum TxGH116. The structure of this protein alone and in a covalent complex with 2-fluoroglucose and noncovalent complexes with glucoimidazole, deoxynojirimycin and glucose, allowed us to identify the glycon-binding residues or the active site. A model of human GBA2 based on these structures allowed us to explain the molecular basis for its defects leading to hereditary spastic paraplegia and autosomal recessive congenital ataxia, while the human defects identified a catalytically important residue on the fringe of the active site.

References

[1] Sansenya S, Mutoh R, Charoenwattanasatien R, Kurisu G, Ketudat Cairns JR. (2015) Expression and crystallization of a bacterial glycoside hydrolase family 116 beta-glucosidase from Thermoanaerobacterium xylanolyticum. Acta Crystallogr. Sect. F 71 (1), 41-44.

BIOGRAPHY

2011-present: Professor, School of Biochemistry, Suranaree University of Technology, Thailand
2005-2011: Associate Professor, Schools of Chemistry and Biochemistry, Suranaree University of Technology, Thailand
1998-2005: Assistant Professor, School of Chemistry, Suranaree University of Technology
1996-present: Researcher, Laboratory of Biochemistry, Chulabhorn Research Institute, Thailand
1995-1998: Lecturer, School of Chemistry Suranaree University of Technology, Thailand
1993-1994: Postdoctoral fellow, Department of Chemistry & Center for Molecular Genetics, University of California, San Diego
1993: PhD, University of California, San Diego, USA

Research Fields and Interests:
Simple and complex carbohydrates play important roles in living organisms, including energy storage and transfer, structural, signalling and defensive roles. Carbohydrate active enzymes act to modify the structure and activities of carbohydrates. In my group, we investigate the roles of beta-glucosidases and related enzymes in rice, since carbohydrates and glycoconjugates have the widest variety of structures and functions in plants. We are interested to learn both the biochemical and biological functions of these enzymes, as well as the molecular interactions leading to their specific enzymatic functions. In work with Prof. Jisnuson Svasti in the Biochemistry Laboratory of Chulabhorn Research Institute, we study the molecular defects leading to inborn errors of metabolism, particularly for carbohydrate degradative enzymes. Recently, we have combined these interests by determining the structure and activity of a bacterial enzyme that can serve as a model for both human and plant beta-glucosidases belonging to glycoside hydrolase family 116.

Selected Publications:

Hua Y, Ekkhara W, Sansenya S, Srisomsap C, Roytrakul S, Saburi W, Takeda R, Matsuura H, Mori H, Ketudat Cairns JR. (2015) Identification of rice Os4BGlu13 as a β-glucosidase which hydrolyzes gibberellin A4 1-O--D-glucosyl ester, in addition to tuberonic acid glucoside and salicylic acid derivative glucosides. Arch. Biochem. Biophys. (Accepted 30 July, 2015)

Komvongsa J, Luang S, Marques JV, Phasai K, Davin LB, Lewis NG, Ketudat Cairns JR. (2015) Active site cleft mutants of Os9BGlu31 transglucosidase modify acceptor substrate specificity and allow production of multiple kaempferol glycosides. Biochim. Biophys. Acta, Gen. Subj. 1850 (7), 1405–1414.

Pengthaisong S, Ketudat Cairns JR. 2014. Effects of active site cleft residues on oligosaccharide binding, hydrolysis, and glycosynthase activities of rice BGlu1 and its mutants. Protein Sci. 23, 1738-1752.

Tankrathok A, Iglesias-Fernández J, Luang S, Robinson R, Kimura A, Rovira C, Hrmova M, Ketudat Cairns J. 2013. Structural analysis and insights into glycon specificity of the rice GH1 Os7BGlu26 -D-mannosidase. Acta Crystallogr. Sect. D. D69 (10), 2124-2135.

Luang S, Cho J-I, Mahong B, Opassiri R, Akiyama T, Phasai K, Komvongsa J, Sasaki N, Hua Y, Matsuba Y, Ozeki Y, Jeon J-S, Ketudat Cairns JR. 2013. Os9BGlu31 is a transglucosidase with the capacity to equilibrate phenolpropenoid, flavonoid and phytohormone glycoconjugates. Journal of Biological Chemistry 288(14), 10111- 10123