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  • Author or Editor: Robert P. Walker x
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Although information is available regarding the content of various metabolites such as sugars and organic/amino acids in blackberry (Rubus L.), little is known about its enzyme composition. The aim of this study was to investigate changes in the abundance of various enzymes during the ripening of blackberry. Blackberry is an aggregate fruit, composed of a receptacle and several drupelets attached to it, which in turn, are composed of the flesh (mesocarp plus epicarp) and seed enclosed in the endocarp; therefore, these parts were analyzed separately along with the pedicel. The enzymes studied participate in organic/amino acid and sugar metabolism and photosynthesis, processes known to be important in fruit development. These enzymes were phosphoenolpyruvate carboxykinase [PEPCK (EC:], phosphoenolpyruvate carboxylase [PEPC (EC:], pyruvate, orthophosphate dikinase [PPDK (EC:], cytosolic aspartate aminotransferase [cyt AspAT (EC:], aldolase (EC:, glutamine synthetase [GS (EC:], and ribulose-1,5-bisphosphate carboxylase/oxygenase [RUBISCO (EC:]. To avoid problems in measuring enzyme activity, the approach taken was to use antibodies specific for each enzyme in conjunction with immunoblotting of sodium dodecyl sulfate polyacrylamide gel electrophoresis. During ripening, there were marked changes in abundance of several of these enzymes and these changes were dependent on the tissue investigated. PEPCK appeared when organic acids decreased in the flesh and was only detected in this tissue, whereas PPDK was not detected in any tissue. In the flesh, there was a large decrease in abundance of RUBISCO, plastidic GS, and plastidic aldolase, but little change in cytosolic GS, cytosolic aldolase, and PEPC. In seeds, there was a decrease in the abundance of all enzymes. In the receptacle and pedicel, apart from a large decrease in RUBISCO in the receptacle, there was little change in enzyme abundance.

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Key nutritional characteristics of the fruit flesh of 41 sour cherries growing in the region of Umbria in central Italy have been determined. Fruit size, flesh dry matter content, nonstructural carbohydrates, organic acids, and anthocyanins were the analyzed parameters. Both the growing environment and genotype were statistically significant for most of the characteristics. Morello sour cherries were characterized by a large amount of sorbitol (up to 44.2 mg·g−1 FW), which contributed significantly to the dry matter content of the flesh, malic acid content that was higher (up to 48.4 mg·g−1 FW) than any published values for cherry flesh, and high anthocyanin content (up to 383.4 mg per 100 g FW). Cyanidin 3-glucosyl rutinoside was the most abundant compound. The analyzed germplasm could be the basis for breeding programs and new industrial products with high nutritional value.

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