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United States Department of Agriculture

Agricultural Research Service


item Cote, Gregory - Greg
item Ahlgren, Jeffrey

Submitted to: Carbohydrate Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Alternan is a water-soluble gum that is being considered as a replacement for imported gum arabic and as a low-calorie bulking agent in foods. While studying the microbial digestion of alternan, it was discovered that some of the products had unusual chemical structures. These products were found to be cyclic (ring-shaped) sugars, which is very unusual for compounds of this type. Our previous studies reported on the production of these ring-shaped sugars from alternan. We have now found that they can also be produced from other sugars, including some derived from starch. This work shows that these novel and potentially useful compounds can be produced not only from cane and beet sugar, but also from starch and starch-derived materials. The results are of potential value to starch-producers and reveal information about the basic biochemistry of this class of enzymes.

Technical Abstract: Alternanase is an enzyme which endo-hydrolytically cleaves the alpha(1-3), alpha(1-6)-linked D-glucan alternan. The main products are isomaltose, alpha-D-Glcp-(1-3)-alpha-D-Glcp-(1-6)-D-Glc and the cyclic tetrasaccharide cyclo{-6)-alpha-D-Glcp-(1-3)-alpha-D-Glcp-(1-6)-alpha-D-Glcp-(1-3)-alpha-D- Glcp-(1-}. It is also capable of acting on oligosaccharide substrates. The cyclic tetrasaccharide is slowly hydrolyzed to isomaltose. Panose and the trisaccharide alpha-D-Glcp-(1-6)-alpha-D-Glcp-(1-3)-D-Glc both undergo transglycosylation reactions to give rise to the cyclic tetrasaccharide plus D-glucose, with panose being converted at a much faster rate. The tetrasaccharide alpha-D-Glcp-(1-3)-alpha-D-Glcp-(1-6)-alpha-D-Glcp-(1-4)-D- Glc is hydrolyzed to D-glucose plus the trisaccharide alpha-D-Glcp-(1-3)- alpha-D-Glcp-(1-6)-D-Glc. Alternanase does not act on isomaltotriose, theanderose, or alpha-D-Glcp-(1-6)-alpha-D-Glcp-(1-6)-alpha-D-Glcp-(1-4)- alpha-D-Glc. The enzyme releases 4-nitrophenol from 1-O-(4-nitrophenyl) alpha-isomaltoside, but not from 1-O-(4-nitrophenyl) alpha-D- glucopyranoside, 1-O-(4-nitrophenyl) alpha-isomaltotrioside, or 1-O-(4- nitrophenyl) alpha-isomaltotetraoside.

Last Modified: 06/28/2017
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