Antitumor activities and immunochemical properties of the cell-wall polysaccharides from Aureobasidium pullulans

Delipidated cell walls from Aureobasidium pullulans were fractionated systematically. The cell surface heteropolysaccharide contains D-mannose, D-galactose, D-glucose, and D-glucuronic acid (ratio, 8.5:3.9:1.0:1.0). It consists of a backbone of (1-->6)-alpha-linked D-mannose residues, some of which are substituted at 0-3 with single or beta-(1-->6)-linked D-galactofuranosyl side chains, some terminated with a D-glucuronic acid residue, and also with single residues of D-glucopyranose, D-galactopyranose, and D-mannopyranose. This glucurono-gluco-galactomannan interacted with antiserum against Elsinoe leucospila, which also reacted with its galactomannan, indicating that both polysaccharides contain a common epitope, i.e., at least terminal beta-galactofuranosyl groups and also possibly internal beta-(1-->6)-linked galactofuranose residues. It was further separated by DEAE-Sephacel column chromatography to gluco-galactomannan and glucurono-gluco-galactomannan. The alkali-extracted beta-D-glucan was purified by DEAE-cellulose chromatography to afford two antitumor-active (1-->3)-beta-D-glucans. One of the glucans (M(r), 1-2 x 10(5)) was a O-6-branched (1-->3)-beta-D-glucan with a single beta-D-glucosyl residue, d.b., 1/7, and the other (M(r), 3.5-4.5 x 10(5)) had similar branched structure, but having d.b., 1/5. Side chains of both glucans contain small proportions of beta-(1-->6)- and beta-(1-->4)-D-glucosidic linkages.