Oxidative enzyme activities and soluble protein content in leaves and fruits of olives during ripening

Changes in the content and composition of soluble proteins and the activities of ionically bound peroxidase and polyphenoloxidase in leaves and fruits of olive trees Olea europaea cv. Zard from three regions during "on" and "off" years were evaluated. It was shown that peroxidase and polyphenoloxidase activities were low at early fruit developmental stages, gradually increased and were the highest at full fruit development (120-135 days after fruit set), and remained relatively high throughout ripening and softening stage. Polyacrylamide gel electrophoresis was used for characterization of peroxidase and polyphenoloxidase enzymes in leaf and fruit extracts. Isoenzymes were assessed in extracts from different regions and it was observed that some isoenzymes were only present at full fruit maturity. The protein content and its expression was estimated and characterized, and it was shown that protein content increased during various stages of fruit growth and remained the highest at full fruit ripening. The increase in enzyme activity from leaves and fruits was accompanied by differential expression of isoenzymes and the protein bands between 20 to 37 KDa, that seems to be a marker of full fruit maturity. It was also concluded that in all cases protein content and enzyme activities in leaves and fruits of olive trees during "on" years are considerably lower than those during "off" years.