Purification and characterization of an exo-polygalacturonase from the tomato vascular wilt pathogen Fusarium oxysporum f sp lycopersici

An exo-polygalacturonase (EC 3:2.1.15) was purified to apparent homogeneity from cultures of Fusarium oxysporum f.sp. lycopersici on synthetic medium supplemented with citrus pectin, using preparative isoelectric focusing. The enzyme, denominated PG2, bad an apparent M(r) of 74 000 Da upon SDS-PAGE. The pI of the main PG2 isoform was 4.5, and pH and temperature optima were 5.0 and 55 degrees C, respectively. PG2 hydrolyzed polygalacturonic acid in an exo-manner, as demonstrated by anaysis of degradation products. The enzyme was N-glycosylated. The N-terminal amino acid sequence, L-A-F-N-V-P-S-K-P-P, has no identity to other known polygalacturonases.