PURIFICATION OF PECTATE LYASE PRODUCED BY COLLETOTRICHUM-GLOEOSPORIOIDES AND ITS INHIBITION BY EPICATECHIN - A POSSIBLE FACTOR INVOLVED IN THE RESISTANCE OF UNRIPE AVOCADO FRUITS TO ANTHRACNOSE

Pectate lyase (PL) from Colletotrichum gloeosporioides was purified to apparent homogeneity by hydrophobic interaction chromatography follow ed by isoelectric focusing. The purified preparation showed one band c orresponding to 40 kD on sodium dodecyl sulfate-polyacrylamide gels. T he isoelectric point of the enzyme was 7.9, and the optimum pH for act ivity was 8.9. The purified PL efficiently macerated unripe avocado fr uit wedges. In vitro translation of mRNA from an induced fungal cultur e revealed a 36-kD precursor polypeptide, which was precipitated with PL antibodies. The antibodies inhibited enzymatic activity and macerat ion ability on avocado wedges. Epicatechin, a flavan 3-ol present in t he peel of unripe avocado fruit, had a K-i of 3.4 mu M for inhibition of PL activity in vitro. At 20 mu g/ml (68 mu M), epicatechin reduced the enzyme's macerating ability by 64%. Since the flavan is present in unripe fruit at much higher concentrations (about 350 mu g/g fresh we ight) than the inhibitory concentrations, epicatechin may be involved in the resistance of unripe avocado fruits by inhibiting the PL activi ty of C. gloeosporioides.