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United States Department of Agriculture

Agricultural Research Service

Title: Enzymatic Production of a Cyclic Glucotetrasaccharide Derived from Alternan

Authors
item Ahlgren, Jeffrey
item COTE, GREGORY

Submitted to: Society of Industrial Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: August 15, 2002
Publication Date: N/A

Technical Abstract: When the enzyme alternanase hydrolyzes alternan, a microbial polysaccharide composed of alpha-D-glucose, the main product is a novel cyclic tetrasaccharide that maintains the alternating alpha-(1-6), alpha-(1-3) linkages found in native alternan. An analysis of this reaction revealed that the enzyme cleaves the alpha-(1-3) linkages of alternan but not the alpha-(1-6) linkages, since isomaltose {alpha-D-glucose-(1-6)-alpha-D-glucose} was also found as a product of hydrolysis. Other substrates can be hydrolyzed by alternanase to form the cyclic tetrasaccharide; 2 moles of the trisaccharide panose {alpha-D-glucose-(1-6)-alpha-D-glucose-(1-4)-alpha-D-glucose} can be converted into one mole of cyclic tetrasaccharide with alternating alpha-(1-6), alpha-(1-3) linkages and 2 moles of free glucose, suggesting that alternanase was also capable of hydrolyzing an alpha-(1-4) linkage adjacent to an alpha-(1-6)-linked glucose. This was further demonstrated by the observation that alternanase can act on reuteran, an exopolysaccharide from Lactobacillus reuteri LB121, which contains alpha-(1-4), alpha-(1-6), and 4,6-branched glucose residues, to form the cyclic tetrasaccharide. Further modifications of the cyclic tetrasaccharide can be achieved enzymatically; the enzyme alpha-galactosidase can catalyze an efficient 6-O-alpha-D-galactopyranosylation of the cyclic tetrasaccharide, opening possibilities for future studies.

Last Modified: 9/10/2014
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