Digestive proteolytic activity in larvae and adults of Bactrocera oleae Gmelin (Diptera: Tephritidae)

Digestive proteolytic activity in larvae and adults of Bactrocera oleae was studied using specific substrates and inhibitors. The optimal pH for general proteolytic activity was 4 and 10 for soluble and membrane-bound fractions of larvae, and 9 for the soluble fraction of adults. The highest activities of general proteases were revealed at temperatures of 25 °C and 45 °C for both the soluble and membrane-bound fractions of larvae as well as the soluble fraction of adults. Determination of the specific protease activities demonstrated the presence of serine and cysteine proteases in addition to two exopeptidases in the larvae and adults. However, trypsin-like protease, chymotrypsin-like protease, and two exopeptidases of larvae, and chymotrypsin-like protease as well as cathepsin L of adults had no activity in the soluble fraction. The presence of specific proteases was verified by using specific inhibitors such as PMSF, TLCK, TPCK, E-64, EDTA, phenanthroline, and DTT. Finally, feeding of B. oleae larvae on different olive varieties revealed the highest trypsin-like protease, chymotrypsin-like protease, elastase, cathepsin B, cathepsin L, and cathepsin D on Amigdalifolia, Coratina, Baladi, Mari, Conservalia, Baladi, and Arbequina, respectively. These results showed digestive proteolytic activities in B. oleae for the first time, and could be the basic knowledge required for finding a control procedure to decrease the damage of this destructive pest around the world.