Endopolygalacturonase from Rhizoctonia fragariae. Purification and characterization of two isoenzymes

An electrophoretically homogeneous preparation of endo-polygalacturonase (poly(1,4-alpha-D-galacturonide)glycanohydrolase, EC 3.2.1.15) from culture filtrates of Rhizoctonia fragariae, a pathogenic agent in strawberry plants, was resolved into two isoenzymes when subjected to isoelectrofocusing in a narrow pH range. The isoelectric points of the two isoenzymes were 6.76 +/- 0.03 and 7.08 +/- 0.05. The two polygalacturonases exhibited similar substrate specificity, pH optimum and pattern of degradation of sodium polypectate. The two enzymes consisted of a single polypeptide chain which had an apparent molecular weight of 36 000 as determined by gel filtration on Sephadex G-100.