TAILIEUCHUNG - Báo cáo khoa học: Role of asparagine 1134 in glucosidic bond and transglycosylation specificity of reuteransucrase from Lactobacillus reuteri 121

Glucansucrases from lactic acid bacteria convert sucrose into variousa-glu-cans that differ greatly with respect to the glucosidic bonds present (. dextran, mutan, alternan and reuteran). This study aimed to identify the structural features of the reuteransucrase from Lactobacillus reuteri121 (GTFA) that determine its reaction specificity. | ỊFEBS Journal Role of asparagine 1134 in glucosidic bond and transglycosylation specificity of reuteransucrase from Lactobacillus reuteri 121 Slavko Kralj Wieger Eeuwema Tom H. Eckhardt and Lubbert Dijkhuizen Centre for Carbohydrate Bioprocessing CCB TNO-University of Groningen Haren the Netherlands and Department of Microbiology Groningen Biomolecular Sciences and Biotechnology Institute GBB University of Groningen Haren the Netherlands Keywords glucansucrase Lactobacillus reuteri product specificity reuteransucrase site-directed mutagenesis Correspondence L. Dijkhuizen Department of Microbiology University of Groningen Kerklaan 30 9751 NN Haren the Netherlands Fax 31 50 3632154 Tel 31 50 3632150 E-mail Received 12 May 2006 revised 12 June 2006 accepted 14 June 2006 Glucansucrases from lactic acid bacteria convert sucrose into various a-glu-cans that differ greatly with respect to the glucosidic bonds present . dextran mutan alternan and reuteran . This study aimed to identify the structural features of the reuteransucrase from Lactobacillus reuteri 121 GTFA that determine its reaction specificity. We here report a detailed mutational analysis of a conserved region immediately next to the catalytic Asp1133 putative transition-state stabilizing residue in GTFA. The data show that Asn1134 is the main determinant of glucosidic bond product specificity in this reuteransucrase. Furthermore mutations at this position greatly influenced the hydrolysis transglycosylation ratio. Changes in this amino acid expands the range of glucan and gluco-oligosaccharide products synthesized from sucrose by mutant GTFA enzymes. doi Glucansucrases glucosyltransferases EC from lactic acid bacteria use sucrose to synthesize a diversity of a-glucans with a- 1 fi 6 dextran mainly found in Leuconostoc a- 1 fi 3 mutan mainly found in Streptococcus alternating a- 1 fi 3 and a- 1 fi 6 alternan only reported in Leuconostoc .

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