Purification and characterization of β-1,6-glucanase of Streptomyces rochei application in the study of yeast cell wall proteins

A beta-1,6-glucanase was purified to apparent homogeneity from a commercial yeast digestive enzyme prepared from Streptomyces rochei by a series of column chromatographies. The molecular mass of the purified enzyme was 60 kDa by SDS-PAGE. The purified enzyme had an optimum pH range from 4.0 to 6.0 and was stable in the same pH range. The enzyme was stable under 50degreesC but lost almost all activity at 60degreesC. The enzyme was specific to beta-1,6-glucan and had little activity towards beta-1, 3-glucan and beta-1, 4-glucan. When the beta-1,6-glucan was hydrolyzed with the purified enzyme for 5 h, the reaction products contained 20% glucose, 36% gentiobiose, and 44% other oligosaccharides, suggesting that the enzyme is an endo-type glucanase. When the purified enzyme was used for the digestion of the cell wall of Saccharomyces cerevisiae, cell-wall proteins covalently bound to the cell-wall glucan were recovered as soluble forms, suggesting that this enzyme is useful for analysis of yeast-cell wall proteins.