Cell wall autolysis during kiwifruit development

Abstract

Cell walls prepared from developing kiwifruits showed autolytic activity. The proteins extracted from active walls were also able to release carbohydrates from inactive cell walls. Analysis of the sugars released, using both procedures, showed that uronic acids were the major component, especially during the first hours of incubation, although neutral sugars such as glucose and galactose were also present. Most of the carbohydrates autolytically released from the cell wall eluted in the void volume on a Bio Gel P2 column. However, carbohydrates released from inactive cell walls by the protein extract mostly eluted in the monosaccharide uronic acid and glucose peaks. The autolytic activity of isolated cell walls, as well as the glycosylhydrolase activity of the proteins extracted from the cell walls, showed important changes during fruit development. The differences between autolytic activity and the glycosylhydrolase activity against the cell wall suggest that the glycosylhydrolases 'in muro' are subjected to some regulatory mechanism which disappears with their extraction. Finally, the role of glycosylhydrolases, such as polygalacturonases and galactosidases, in relation to cell wall changes in fruits, is discussed.