RESISTANCE OF HIGHLY BRANCHED (1-]3)-BETA-D-GLUCANS TO FORMOLYSIS

Small molecular weight (MW) glucan derivatives could be a useful tool for studying the mechanisms of beta-glucan mediated biological activit y, especially as antagonists for a beta-glucan receptor. This paper de scribed the stability of various (1-->6) branched (1-->3)-beta-D-gluca ns to formolysis in the preparation of small MW derivatives. The gluca ns used were curdlan (linear), pachyman (few branches), GRN (one branc h in every third main chain unit; 2/6), SPG (2/6), SSG (3/6), and OL-2 (4/6). Curdlan and pachyman were easily degraded to oligosaccharides by degradation for 20 min at 100 degrees C by 90% formic acid. However , branched glucans, especially the highly branched glucans, SSG and OL -2, were significantly resistant to degradation, and the majority rema ined high MW. SSG required a longer period and/or a higher temperature (121 degrees C treatment) to produce small MW derivatives. Branched g lucans were also resistant to zymolyase (an endo-(1-->3)-beta-D-glucan hydrolase) digestion. These facts suggest that the (1-->6)-beta-D-bra nched residues contribute to the glucans' resistance to formic acid de gradation and zymolyase digestion.