CHARACTERIZATION OF AN ENDOPOLYGALACTURONASE PRODUCED BY THE CHESTNUT BLIGHT FUNGUS

Extracellular endopolygalacturonase was produced by Cryphonectria parasitica strain Ep 155 (ATCC No. 38755) in culture media amended with 1% sodium polypectate. Production of the enzyme was stimulated dramatically by 1% glucose, or 0.25% yeast extract and 0.75% malt extract. The enzyme was purified 244-fold to apparent homogeneity by ultrafiltration, cation exchange chromatography on CM-cellulose, and gel filtration on Sephadex G-75. Its molecular weight was approximately 42 kDa as estimated by SDS-PAGE and gel filtration, and its isoelectric point was about pH 8.0. The pH optimum of the enzyme was pH 4.5-5.0, and its optimum temperature was 40 degrees C. The K-m and V-max of the enzyme were 0.22 mg ml(-1) with polygalacturonic acid as substrate, and 0.241 mmol reducing group min(-1) mg(-1) protein, respectively. The enzyme acted in an endo fashion; a 50% reduction in viscosity of polygalacturonic acid resulted in hydrolysis of fewer than 2.5% of the glycosidic bonds.