STRUCTURE OF GLUCOMANNAN-PROTEIN FROM THE YEAST CRYPTOCOCCUS-LAURENTII

The structure of an extracellular glucomannan-protein produced by Cryp tococcus laurentii was studied. The glucomannan-protein was isolated v ia its insoluble copper complex. It was homogeneous on free-boundary e lectrophoresis, contained 91% saccharide, 6.5% protein and 1% phosphor us. It had (M) over bar(n) 21,000. The carbohydrate portion was compos ed of D-mannose and D-glucose in 33:2 molar ratio. From the results of compositional and methylation analyses, conventional acetolysis, as w ell as H-1 and C-13 NMR spectroscopy it was concluded that the glucoma nnan has an alpha-(1-->6)-linked D-mannopyranosyl backbone having most residues (about 83%) substituted at O-2 with one, two, three or four D-mannopyranosyl units connected by alpha-(1-->2) and alpha-(1-->3) li nkages. Moreover, an additional side chain with the -Manp-(l-->3)-D-Ma np-(l-->2)-D-Manp-(1-->2)-D-Manp backbone structure in which alpha-D-g lucopyranose residue is linked to O-2 of the mannopyranose unit next t o the reducing end. Alkali treatment of glucomannanprotein in the pres ence of sodium borohydride showed that 87% serine and 83% threonine re sidues were glycosylated with mannose, mannobiose, and mannotriose.