A lectin extracted from Citrullus colocynthis L. (Cucurbitaceae) inhibits digestive α-amylase of Ectomyelois ceratoniae Zeller (Lepidoptera: Pyralidae)

Abstract

A lectin was extracted from seeds of <em>Citrullus colocynthis</em> (Cucurbitaceae) by column chromatography using Sepharose 4BGalactose and DEAE-Cellulose fast flow. The inhibitory effects of the extracted lectin on digestive α-amylase of <em>Ectomyelois ceratoniae</em> larvae were studied using pH, temperature, time of incubation and kinetic parameters. Different concentrations of extracted lectin, <em>Citrullus colocynthis</em> agglutinin (CCA), inhibited digestive amylolytic activity by 22-49%. The highest inhibition was obtained at pH 8 and 9, which corresponds with the highest enzymatic activity in the control. The highest inhibition of <em>E. ceratoniae</em> α-amylase was found at 40°C, which corresponds with the optimal temperature for enzymatic activity. Timecourse experiments revealed the highest amylolytic activity at 20-40 min post-incubation, while the highest inhibition was found after 20- 30 min. Kinetic analysis showed that incubation of α-amylase with CCA significantly decreased <em>V<sub>max</sub></em>, indicating non-competitive inhibition, but no statistical difference was found in the <em>K<sub>m</sub></em> value. Our results indicated that CCA significantly inhibited activity of digestive α-amylase in <em>E. ceratoniae</em> larvae, suggesting its possible application as a potential alternative control method against this pest.