Enzymes of the yeast lytic system produced byArthrobacter GJM-1 bacterium and their role in the lysis of yeast cell walls

Abstract

Yeast lytic system produced by Arthrobacter GJM-1 bacterium during growth on baker's yeast cell walls contains a complete set of enzymes which can hydrolyze all structural components of cell walls of Saccharomyces cerevisiae. Chromatographic fractionation of the lytic system showed the presence of two types of endo-beta-1,3-glucanase. Rapid lysis of isolated cell walls of yeast was induced only by endo-beta-1,3-glucanase exhibiting high affinity to insoluble beta-1,3-glucans and releasing laminaripentaose as the main product of hydrolysis of beta-1,3-glucans. This enzyme was able to lyse intact cells of S. cerevisiae only in the presence of an additional factor present in the Arthrobacter GJM-1 lytic system, which was identified as an alkaline protease. This enzyme possesses the lowest molecular weight among other identified enzyme components present in the lytic system. Its role in the solubilization of yeast cell walls from the outer surface by endo-beta-1,3-glucanase could be substituted by preincubation of cells with Pronase or by allowing the glucanase to act on cells in the presence of thiol reagents. The mechanism of lysis of intact cells and isolated cell walls by the enzymes of Arthrobacter GJM-1 is discussed in the light of the present conception of yeast cell wall structure.