Purification of polygalacturonases produced by the pear scab pathogens, Venturia nashicola and Venturia pirina

An exopolygalacturonase and three endopolygalacturonases were purified from mycelia of pear scab pathogens, Venturia pirina and Venturia nashicola. Th e molecular weight of the isolated exoPG from V. pirina was 43 kDa, and the endoPGs from V. nashicola were 42 kDa as estimated by SDS-polyacrylamide g el electrophoresis. The pH optimum of the exoPG activity from V. pirina was 5.0. The K-m and V-max values of the exoPG were 0.08 mg ml(-1) and 4.44 x 10(-3) mmol reducing group min(-1) mg protein(-1). The N-terminal amino aci d sequence of the exoPG from V. pirina was similar to that of the exoPG fro m Fusarium oxysporum f. sp. melonis, and the N-terminal amino acid sequence s of the three endoPGs from V. nashicola races 1, 2 and 3 were similar to o ther fungal endoPGs with a conserved motif of ASxxxTFTxAAAxxxG. (C) 2000 Ac ademic Press.