Stable lysozyme-cello-oligosaccharide complexes

Stable complexes that formed when ¹⁴C]cello-oligosaccharides and lysozyme were incubated under various conditions were isolated chromatographically and characterized. Complexation occurred over the pH range of 3–9 but was favored at high pH; the extent of complexation was inversely proportional to temperature. The stoichiometry of the complex was 1:1 sugar-protein, but no radiolabeled peptides could be isolated from a tryptic digest. The minimum requirements for association were native enzyme and a substrate composed of three or more (1→4)-β-D-glucopyranosyl residues. Acceptors and competitive inhibitors of lysozyme inhibited complexation and stimulated dissociation of the complex. Lysozyme did not hydrolyze the cello-oligosaccharides nor did it use them as D-glucosyl donors. Ultracentrifugation, molecular-sieve chromatography, and light-scattering studies indicated that the precipitated complexes were large, heterogeneous aggregates of protein and oligosaccharide which conform to the following equilibrium: n(protein+oligosaccharide)?(protein-oligosaccharide)_n. Polymerization is a cooperative phenomenon.