Concanavalin A as a probe of phosphomannan molecular structure

Abstract

The diploid yeast Hansenula holstii NRRL Y-2448 produces a highly viscous extracellular phosphomannan that does not interact with concanavalin A. Autohydrolysis of the polymer cleaves mannosyl α-l-phospho-6′-mannosyl links to yield mannose 6-phosphate-based oligosaccharides (90%) and a highly phosphorylated core polysaccharide (10%). The core polymer strongly interacts with concanavalin A. Intact phosphomannans produced by mucoid (NRRL Y-2154) and relatively non-mucoid (NRRL Y-2155) parent haploid strains are less viscous and interact with concanavalin A. Autohydrolysis of these polymers also gives rise to oligosaccharide and core phosphomonoesters. These mannan phosphate cores also strongly interact with concanavalin A. The intensities of phosphomannan interactions with concanavalin A likely reflect the extent to which reactive sites in the polymer cores are covered by nonreactive oligosaccharide polyphosphodiester branches.