POTATO BETA-1,3-GLUCANASES PROBABLY PARTICIPATE IN PROTECTION OF THE PLANTS AGAINST PATHOGENS

Two beta-1,3-glucanases (I and II) have been isolated from vacuum extr act of potato leaves. The enzymes have optimum activity at 30 degrees C and pH 5.5. By gel filtration, the molecular weights of glucanase I and glucanase II are 22 and 20 kD, respectively. By electrophoresis un der denaturing conditions, their molecular weights are 30 and 28 kD, r espectively. Inhibitor analysis indicates that tryptophan and dicarbox ylic acid residues are important for the activities of glucanases I an d II. The enzymes are resistant to some natural inhibitors of carbohyd rases. The two enzymes cleave laminaran as endo-specific enzymes, prod ucing oligosaccharides with different degree of polymerization and a t race amount of glucose. Glucanase I has higher viscosimetric activity towards carboxymethylpachyman than glucanase II. The enzymes have tran sglycosylating activity. This capability is probably used in the plant s for the synthesis of elicitors initiating a protection mechanism.