The activities of the fruit ripening enzymes cellulase, polygalacturonase (PG) and pectin methylesterase (PME) were detected during the development of sweet cherry (Prunus avium L.) fruit. Cellulase and PG activities of pericarp tissue increased 4-10 times between hypanthium abscission and harvest. PME activity remained high throughout this period of fruit development. There was a positive correlation between the anthocyanin content of the pericarp and both cellulase and PG activities. Concomitant with the increases in the activities of these ripening enzymes was a decrease in fruit firmness. The increases in cellulase and PG activities were checked following two-weeks storage at 10 C after harvest. The purification and characterization of the putative cellulase and PG enzymes will be discussed, together with attempts to chemically inhibit their activities and modify fruit softening.
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