Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/22/2007
Publication Date: 4/22/2007
Citation: Cote, G.L. 2007. Alternansucrase acceptor products and their applications [abstract]. Seventh Annual Carbohydrate Bioengineering Meeting. Braunschweig, Germany. P. 67.
Technical Abstract: Alternansucrase is one of a family of enzymes known as glucansucrases. These enzymes are promising catalysts for the conversion of sugar to useful, value-added carbohydrates. The terms "alternan" and "alternansucrase" first entered the literature 25 years ago to refer to a unique glucan and its biosynthetic enzyme. What makes alternansucrase (E.C. 22.214.171.124) so unique is its ability to synthesize an alternating sequence of alpha(1,3) and alpha(1,6)-linked D-glucopyranosyl units using sucrose as the donor substrate. While this imparts some peculiar physical and chemical properties to the polysaccharide alternan, less is known about the oligosaccharide products that arise via acceptor reactions. Recent work in our laboratory and others has shown that alternansucrase is capable of producing a variety of unusual oligosaccharides via glucosyl transfer acceptor reactions to various acceptor sugars. The enzyme’s regioselectivity differs from dextransucrase in ways that can be useful for the synthesis of novel oligosaccharide structures. For example, it has been recently shown that the oligosaccharides produced when maltose is the acceptor include one trisaccharide structure, two tetrasaccharides, one pentasaccharide, two hexasaccharides, and one heptasaccharide. This may shed some light on how the enzyme works to produce the alternan structure. Another characteristic of alternansucrase that distinguishes it from dextransucrase is its ability to use leucrose as an acceptor. Leucrose, produced by glucosyl transfer to fructose released from the initial sucrose substrate, represents a dead-end product for dextransucrase. Alternansucrase, however, continues to transfer glucosyl units to leucrose, resulting in some unusual glucosyl-fructose oligosaccharides. We will also discuss our work with alternan oligosaccharides as potential prebiotics for food and feed, and the use of alternan oligosaccharides in the new low-glycemic sweetener Sucromalt.