LIPOXYGENASE ACTIVITY IN RIPENING TOMATO FRUIT PERICARP TISSUE

To determine what role, if any, lipoxygenases might play in the ripeni ng of tomato fruit, the activities of these enzymes were characterized and measured during fruit development. Two distinct lipoxygenase acti vities were identified by their pH optima and their sensitivity to the lipoxygenase inhibitor, nordihydroguaiaretic acid (NDGA), in tomato f ruit pericarp tissue during ripening. Both activities increased sharpl y during early ripening stages and decreased after the fruit had ripen ed fully. Polypeptides with cross-reactivity to pea seed anti-lipoxyge nase B antiserum were detected in ripening pericarp by immunoblotting at times which closely paralleled the observed rise in lipoxygenase ac tivity seen during the development of the tomato fruit. Heterogeneity in the M(r) of these polypeptides and associated changes in the ratio of lipoxygenase activities at different pH optima were observed during ripening and upon storage of tomato fruits.