Peroxidase in unripe and processing-ripe strawberries

The activity, enzymatic polymorphism and tissue localization of peroxidase in unripe and processing-ripe strawberries (Fragaria ananassa var. Oso Grande) was studied. The results showed that both unripe and processing-ripe strawberries contain a peroxidase isoenzyme of basic pI, which is the only component of peroxidase polymorphism in the fruits and which is mainly localized in the concentric array of the vascular bundles and in the vascular connections with the seeds. This isoenzyme is also located in the epidermal cells. The activity of this basic peroxidase isoenzyme, which is apparently bound to acidic polysaccharides during extraction and from which it may be solubilized by treatment with Caylase 345L, did not vary with ripening. From these results, it may be concluded that this basic peroxidase isoenzyme, similar to its homologous isoenzyme in grape berries, is involved in the lignification of the vascular tissues during fruit development.