The hydrolytic and transferase action of alternanase on oligosaccharides

Alternanase is an enzyme which endo-hydrolytically cleaves the alpha-(1 --> 3), alpha-(1 -->6)-linked D-glucan, alternan. The main products are isomalt ose, alpha -D-Glcp-(1 -->3)-alpha -d-Glcp-(1 -->6)-D-Glc and the cyclic tet rasaccharide cyclo (--> 6)-alpha -D-Glcp-(1 -->3) -alpha -D-Glcp-(1 -->6)-a lpha -D-Glp(1 --> 3)-alpha -d-Glcp-(1 --> ). It is also capable of acting o n oligosaccharide substrates. The cyclic tetrasaccharide is slowly hydrolyz ed to isomaltose. Panose and the trisaccharide alpha -D-Glcp-(1 -->6)-alpha -D-GLcp-(1 -->3)-D-Glc both undergo transglycosylation reactions to give r ise to the cyclic tetrasaccharide plus D-glucose, with panose being convert ed at a much faster rate. The tetrasaccharide alpha -D-Glcp-(1 --> 3)-alpha -D-Glcp-(1 -->6)alpha -D-Glc-(1 --> 6)-D-Glc is hydrolyzed to D-glucose pl us the trisaccharide alpha -D-Glcp-(1 -->3)-alpha -D-Glcp-(1 --> 6)-D-Glc. Alternanase does nut act on isomaltotriose, theanderose (6(Glc)-O-alpha -D- Glcp sucrose), or alpha -D-Glcp-(1 -->6)-alpha -D-Glcp(1 -->6)-alpha -D-Glc p-(1 -->)-alpha -D-Glc, The enzyme releases 4-nitrophenol from 4-nitropheny l alpha -isomaltoside, but not from 4-nitrophenyl alpha -D-glucopyrailoside , 4-nitrophenyl alpha -isomaltotrioside, or 4-nitrophenyl alpha -isomaltote traoside. (C) 2001 Elsevier Science Ltd. All rights reserved.