POLYGALACTURONASE AND PECTIN METHYLESTERASE EXTRACTED FROM SWEET GREEN, RED AND YELLOW PEPPERS

Native from the Americas, sweet pepper is a Solanaceous fruit belonging to the Capsicum annuum L. species, whose consumption is most popular in Sicily, mainly due to its occurrence in a wide variety of sunny colours (ranging from green, yellow and red), shapes, and sizes and its characteristic flavour. Sweet peppersare used with eggplants as principal ingredients to produce typical ‘caponata’ a Sicilian relish made of chopped cooked vegetables,mixed with capers and olive oil. Unfortunately, fresh sweet pepper, like other fruit or vegetable, is perishable and therefore not suitable for long-term storage. Softening during storage is typicallyaccompanied by the degradation of the middle lamella and loss of cell adhesion. This process derives from the solubilization of cellwall pectin involving the action of cell wall hydrolytic enzymespectin methylesterase (PME, EC 3.1.1.11) and polygalacturonase(PG, EC 3.2.1.15). PME catalyzes the elimination of methanol from pectin and enables the activity of other endo-acting cell wallenzymes such as PG, which catalyzes the degradation of polygalacturonic acid. Decreasing levels of esterification and hydrolysisof pectin are crucial to the softening of fruits. This study compares PME and PG activities of Sicilian sweet Green peppers at commercial ripening with Red and Yellow ones during chilled storage (4.0◦C, 95% R.U.). PME activity followed the increasing order,Red < Yellow < Green sweet peppers. Yellow fruits seemed to be less affected by PME, whilst absence of this activity in Red pepperscan be due to absence of the enzyme, or to the occurrence of a well-known PME inhibitor, a glycoprotein that usually appearsor increases its amount with ripening. PG activity followed the increasing order, Yellow < Green < Red sweet peppers. Results sug-gest that there is no direct relationship between these two enzymes analyzed.