The hydrolytic and transferase action of alternanase on oligosaccharides Original Research Article

Alternanase is an enzyme which endo-hydrolytically cleaves the α-(1→3), α-(1→6)-linked d-glucan, alternan. The main products are isomaltose, α-d-Glcp-(1→3)-α-d-Glcp-(1→6)-d-Glc and the cyclic tetrasaccharide cyclo{→6)-α-d-Glcp-(1→3)-α-d-Glcp-(1→6)-α-d-Glcp-(1→3)-α-d-Glcp-(1→}. It is also capable of acting on oligosaccharide substrates. The cyclic tetrasaccharide is slowly hydrolyzed to isomaltose. Panose and the trisaccharide α-d-Glcp-(1→6)-α-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 α-d-Glcp-(1→3)-α-d-Glcp-(1→6)-α-d-Glcp-(1→4)-d-Glc is hydrolyzed to d-glucose plus the trisaccharide α-d-Glcp-(1→3)-α-d-Glcp-(1→6)-d-Glc. Alternanase does not act on isomaltotriose, theanderose (6Glc-O-α-d-Glcp sucrose), or α-d-Glcp-(1→6)-α-d-Glcp-(1→6)-α-d-Glcp-(1→4)-α-d-Glc. The enzyme releases 4-nitrophenol from 4-nitrophenyl α-isomaltoside, but not from 4-nitrophenyl α-d-glucopyranoside, 4-nitrophenyl α-isomaltotrioside, or 4-nitrophenyl α-isomaltotetraoside.