Glycosidases in Cell Wall-degrading Extracts of Ripening Tomato Fruits

Abstract

Enzyme preparations were obtained from cell wall debris of tomato (Lycopersicon esculentum L. cv. Tropic) fruits at various stages of ripeness and were assayed for glycosidase and polysaccharidase activities. In addition to polygalacturonase (mol wt 40,000), ripening fruits contain beta-galactosidase (mol wt 63,000) and beta-1, 3-glucanase (mol wt 12,000). The beta-glycosidases, unlike polygalacturonase, are active in extracts of green fruits. Placental tissue shows very low polygalacturonase but increasing beta-galactosidase and beta-1, 3-glucanase activities as ripening proceeds. A large change in the susceptibility of the walls to hydrolase action occurs before the stage in which the greatest polygalacturonase activity occurs. The possibility that the beta-glycosidases contribute to the wall modifications that lead to fruit softening is discussed.