THE EXTRACELLULAR POLYSACCHARIDE OF PICHIA (HANSENULA) HOLSTII NRRL Y-2448 - THE STRUCTURE OF THE PHOSPHOMANNAN BACKBONE

The phosphomannan core of the exopolysaccharide of Pichia (Hansenula) holstii NRRL Y-2448 was isolated after hydrolytic removal of the oligo saccharide phosphate side-chains. The core polysaccharide and its deph osphorylated derivative were subjected to extensive 1D and 2D NMR spec troscopy which yielded information on the linkage sites and on the seq uence of the mannosyl residues in the major oligosaccharide repeating unit. The most probable structure for the repeating unit was (1-->2)]- alpha-D-Man-(1-->2)]-alpha-D-Man-(1-->6)- A semiquantitative conformat ional analysis was performed by Monte Carlo simulations and the result was confirmed by comparison with the experimentally determined NMR da ta, The distance distribution for the phosphate groups was determined from the modelling and was found to cover the expected range of distan ces for phosphorylated high-mannose oligosaccharides. (C) 1996 Elsevie r Science Ltd.