Characterization of two endopolygalacturonase isozymes produced by Fusarium oxysporum f. sp. lycopersici

Abstract

Polygalacturonase (EC 3.2.1.15) produced by Fursarium oxysporum f. sp. lycopersici was purified by chromatography on DEAE-cellulose, CM-cellulose, and hydroxyapatite. The purified enzyme consisted of two electrophoretically distinct "isozymes", that behaved as charge isomers during electrophoresis in several different concentrations of polyacrylamide gel. The two isozymes had similar "endo" modes of action on polygalacturonic acid, as determined by comparison of viscosity reduction, reducing group release, and thin-layer chromatography of oligomeric hydrolysis products. Both isozymes hydrolzyed 5% of the substrate bonds in reaching 50% viscosity reduction. The amino acid compositions of the isozymes were similar and their molecular weights were about 37000 as determined by sedimentation equilibrium. Removal of large amounts of carbohydrate during purification did not affect heat stability of the enzymes. A large proportion of the remaining carbohydrate appeared to be covalently linked to the enzyme protein.