Lysis of yeast cell-walls: non-lytic and lytic (1→6)-β-D-glucanases from Bacillus circulans WL-12

Two types of extracellular (1?6)-ß-D-glucanases are produced by Bacillus circulans WL-12, and these enzymes are differentiated by their ability to lyse yeast cell-walls. The non-lytic (1?6)-ß-D-glucanase was isolated by a combination of Sephadex G-100, Bio-Gel P-100, and DEAE-Bio-Gel A chromatography. The purified enzyme was eloctrophoretically homogeneous and had a molecular weight of 52,000. For the substrate pustulan, the enzyme exhibited the following kinetic properties: pH, 5.0; K_m, 0.83 mg of pustulan/ml; V_max, 104 microequivalents of D-glucose released/min/mg of protein. Pustulan was hydrolysed by an endo-mechanism, producing D-glucose and gentiobiose as preponderant final products. The non-lytic enzyme was specific for the (1?6)-ß-D-glucosidic linkage and did not hydrolyse branched, (1?3)-ß-D-linked glucans containing (1?6)-interchain linkages. In contrast, the lytic (1?6)-ß-D-glucanase produced D-glucose, gentiobiose, and gentiotriose as the final products of pustulan hydrolysis, and exhibited significant activity on branched (1?3)-ß-D-glucans having (1?6)-interchain linkages. In these cases, the major products were gentiobiose and D-glucose, suggesting an ability of the lytic enzyme to cleave some (1?3)-linkages surrounding a (1?6)-branch-point. This latter property may explain the ability of this enzyme to weakly lyse yeast cell-walls. © 1978.