An extracellular galactoxylomannan of acapsular Cryptococcus laurentii mutant

An extracellular galactoxylomannan (GalXM) composed of D-Gal (34.0%), D-Xyl (26.6%) and D-Man (31.0%), and a small amount of L-Ara (4.0%) and D-Glc (4.4%) has been isolated from culture medium of acapsulated mutant of Cryptococcus laurentii by ethanol precipitation and gel filtration. Phosphorylated polymer of Mw approximately 75,000 contained 90% carbohydrates, 3.9% phosphorus and 5.3% proteins. Results of chemical and spectroscopic studies showed a highly branched structure of GalXM with a 1,6-linked mannopyranosyl-galactopyranosyl backbone (approximately 44%) branched predominantly at C-2 and C-3 of mannosyl, and C-3 of galactosyl residues by side chains terminated mainly by xylosyl and mannosyl residues, and to a less extent by arabinosyl and glucosyl ones.