A DIGESTIVE PHOSPHOLIPASE-A2 IN LARVAL MOSQUITOS, AEDES-AEGYPTI

We report on the presence of phospholipase A(2) activity in whole larv a and midguts of the yellow fever mosquito Aedes aegypti. Phospholipas e A(2) is responsible for hydrolyzing fatty acids from the sn-2 positi on of dietary phospholipids to release essential fatty acids for norma l larval and adult growth. In contrast to the mammalian digestive phos pholipase A(2) background, the Ae. aegypti phospholipase A(2) was Ca2-independent. We further characterized the mosquito midgut phospholipa se A(2) by altering the reaction conditions including incubation time, protein concentrations, pH and temperature. The site-specific PLA(2) inhibitor oleyloxyethylphosphorylcholine failed to inhibit the enzyme at concentrations up to 5000 mu M. We found that the phospholipase A(2 ) activity was consistently high throughout the fourth instar, but fel l to very low levels on the first day of pupation which is a non-feedi ng stage. The enzyme is regulated with respect to feeding activity bec ause fasting and re-feeding modified the larval digestive PLA(2) activ ity. (C) 1998 Elsevier Science Ltd. All rights reserved.