A Midgut Digestive Phospholipase A₂in Larval Mosquitoes,<i>Aedes albopictus</i>and<i>Culex quinquefasciatus</i>

Abstract

Phospholipase A 2 (PLA 2 ) is a secretory digestive enzyme that hydrolyzes ester bond at sn-2 position of dietary phospholipids, creating free fatty acid and lysophospholipid. The free fatty acids (arachidonic acid) are absorbed into midgut cells. Aedes albopictus and Culex quinquefasciatus digestive PLA 2 was characterized using a microplate PLA 2 assay. The enzyme showed substantial activities at 6 and 8 μ g/ μ l of protein concentration with optimal activity at 20 and 25 μ g/ μ l of substrate concentration in Aedes albopictus and Culex quinquefasciatus , respectively. PLA 2 activity from both mosquitoes increased in a linear function up to 1 hour of the reaction time. Both enzymes were sensitive to pH and temperature. PLA 2 showed higher enzyme activities in pH 8.0 and pH 9.0 from Aedes albopictus and Culex quinquefasciatus , respectively, at 40°C of incubation. The PLA 2 activity decreased in the presence of 5 mM (Aedes albopictus) and 0.5 mM (Culex quinquefasciatus) site specific PLA 2 inhibitor, oleyloxyethylphosphorylcholine. Based on the migration pattern of the partially purified PLA 2 on SDS-PAGE, the protein mass of PLA 2 is approximately 20–25 kDa for both mosquitoes. The information on PLA 2 properties derived from this study may facilitate in devising mosquitoes control strategies especially in the development of inhibitors targeting the enzyme active site.