Changes in oxygen-scavenging systems and membrane lipid peroxidation during maturation and ripening in blackberry.

Maturation and ripening of blackberry (Rubus sp.) fruit was accompanied by decreased activities of oxygen-scavenging enzymes [superoxide dismutase (EC 1.15.1.1), glutathione-peroxidase (EC 1.11.1.9), catalase (EC 1.11.1.6)] and enzymes in the ascorbate-glutathione cycle [ascorbate peroxidase (EC 1.11.1.11), monodehydroascorbate reductase (EC 1.6.5.4), dehydroascorbate reductase (EC 1.8.5.1), and glutathione reductase (EC 1.6.4.2)]. Nonenzyme components in the ascorbate-glutathione cycle such as ascorbate (AsA), dehydroascorbate (DHAsA), glutathione (GSH), and oxidized glutathione (GSSG) and the ratios of AsA/DHAsA, GSH/GSSG were also decreased. These decreases in antioxidant capacity were correlated with increases in the ratios of saturated to unsaturated fatty acid of polar lipids and free sterols to phospholipids, thus contributing to decreased fluidity, enhanced lipid peroxidation, and membrane deterioration, which may be associated with ripening and senescence in blackberry fruit.