Digestive α-amylase of Bacterocera oleae Gmelin (Diptera: Tephritidae): Biochemical characterization and effect of proteinaceous inhibitor

Abstract

Digestive α-amylase of Bacterocera oleae larvae was characterized and treated by an inhibitor to gain a better understanding of the degradation of nutritional molecules as a potential target for controlling the pest. Presence of α-amylase was confirmed in the gut of olive fruit fly through the use of a negative control in dinitrosalicylic acid procedure. An optimal pH of 5 was found for amylolytic activity in the gut. The enzyme had optimal activity in a broad range of temperatures 20–45°C. Among used cations and specific inhibitors, Ca2+, phenylmethylsulphonyl fluoride (PMSF) and ethylene glycol-bis (β-aminoethylether) N,N,N′,N′-tetraacetic acid (EGTA) had statistical differences on amylolytic activity indicating the presence of amino acid triad and Ca2+ in active site of the enzyme. A proteinaceous α-amylase inhibitor was extracted from Polygonum persicaria, a medicinal plant, that widely grows in North of Iran. IC50 value of PPAI was 0.062mg/ml (i.e. 0.062mg/ml of extracted inhibitor inhibited 50% of amylolytic activity in the gut of B. oleae larvae) and was temperature and pH dependent. The use of enzyme inhibitors from different plant sources may serve as an important pest control strategy via plant breeding programs. Identification of genes responsible for these inhibitor proteins could be a first step to provide a resistant variety of olive.