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. C. Wattad. Department of Post Harvest Science of Fresh Produce, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel. A. Dinoor(2) and D. Prusky(1). (1)Department of Post Harvest Science of Fresh Produce, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel, and (2)Department of Plant Pathology and Microbiology, Faculty of Agriculture, Hebrew University of Jerusalem, P.O. Box 12, Rehovot, Israel. MPMI 7:293-297. Accepted 2 December 1993 1994. Copyright The American Phytopathological Society.

Pectate lyase (PL) from Colletotrichum gloeosporioides was purified lo apparent homogeneity by hydrophobic interaction chromatography followed by isoelectric focusing. The purified preparation showed one band corresponding to 40 kD on sodium dodecyl sulfate-polyacrylamide gels. The isoelectric point of the enzyme was 7.9, and the optimum pH for activity was 8.9. The purified PL efficiently macerated unripe avocado fruit wedges. In vitro translation of mRNA from an induced fungal culture revealed a 36-kD precursor polypeptide, which was precipitated with PL antibodies. The antibodies inhibited enzymatic activity und maceration ability on avocado wedges. Epicatechin, a flavan 3-ol present in the peel of unripe avocado fruit, had a K_i of 3.4 (uM for inhibition of PL activity in vitro. At 20 Mg/ml (68 uM), epicatechin reduced the enzyme's macerating ability by 64%. Since the flavan is present in unripe fruit al much higher concentrations (about 350 (ug/g fresh weight) than the inhibitory concentrations, epicatechin may be involved in (he resistance of unripe avocado fruits by inhibiting the PL activity of C. gloeosporioides.