IMPROVEMENT OF BACTERIAL BETA-GLUCANASE THERMOSTABILITY BY GLYCOSYLATION

The relationship between enzyme stability and glycosylation was examined for two different Bacillus (1,3-1,4)-beta-glucanases following expression of the corresponding genes in Escherichia coli and in Saccharomyces cerevisiae. Both of the (1,3-1,4)-beta-glucanases secreted from yeast cells were glycosylated and a pronounced difference in the type and extent of glycosylation was observed. Thermostability analysis of the glycosylated enzymes and their unglycosylated counterparts synthesized by E. coli disclosed a substantially higher thermotolerance of the glycosylated enzymes. At 70-degrees-C the half-life of the glycosylated form of B. macerans (1,3-1,4)-beta-glucanase was 26 min, as compared to 10 min for the unglycosylated form of the enzyme. Using the same conditions, the half-life of the B. amyloliquefaciens-B. macerans hybrid (1,3-1,4)-beta-glucanase was 5 min for the unglycosylated enzyme and about 100 min when the enzyme was glycosylated.