LIPOXYGENASE ACTIVITY IN RIPENING TOMATO FRUIT PERICARP TISSUE

To determine what role, if any, lipoxygenases might play in the ripening of tomato fruit, the activities of these enzymes were characterized and measured during fruit development. Two distinct lipoxygenase activities were identified by their pH optima and their sensitivity to the lipoxygenase inhibitor, nordihydroguaiaretic acid (NDGA), in tomato fruit pericarp tissue during ripening. Both activities increased sharply during early ripening stages and decreased after the fruit had ripened fully. Polypeptides with cross-reactivity to pea seed anti-lipoxygenase B antiserum were detected in ripening pericarp by immunoblotting at times which closely paralleled the observed rise in lipoxygenase activity 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.