Action of Azotobacter vinelandii poly-beta-D-mannuronic acid C-5-epimeraseon synthetic D-glucuronans

Eleven different glucans (wheat starch, potato amylopectin, potato amylose, pullulan, alternan, regular comb dextran, a-cellulose, microcrystalline ce llulose, CM-cellulose, chitin, and chitosan) that had their C-6 primary alc ohol groups oxidized to carboxyl groups by reaction with 2,2,6,6-tetramethy l-1-piperidine oxoammonium ion (TEMPO), were reacted with Azotobacter vinel andii poly-beta-(1-->4)-D-mannuronic acid C-5-epimerase. All of the oxidize d polysaccharides reacted with the C-5-epimerase, as evidenced by comparing : (1) differences in the relative viscosities; (2) differences in the carba zole reaction; (3) differences in their susceptibility to acid hydrolysis, and (4) differences in their ability to form calcium gels, before and after reaction. We further show the formation of L-iduronic acid from D-glucuron ic acid for oxidized and epimerized amylose by 2D NOESY and COSY + H-1 NMR. (C) 2000 Elsevier Science Ltd. All rights reserved.