Carbodiimide modification enhances activity of pig pancreatic phospholipase A2

Pig phospholipase A2, pig iso-phospholipase A2 and bovine pancreatic phospholipase A2 were reacted in solution with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, in the presence of N-hydroxysulfosuccinimide, at pH 7. The influence of micellar protectants was analyzed. In the presence of n-hexadecylphosphocholine, the losses of activity in micellar diheptanoyl-lecithin were 80, 35, and 10% in bovine phospholipase A2, pig iso-phospholipase A2, and pig phospholipase A2, respectively. With 1-oleoylglycerophosphocholine, the bovine enzyme lost 40% activity, but the pig enzyme was activated sevenfold. The modified pig enzyme showed pre-micellar activation on monomeric diheptanoyl-lecithin, and either reduced or increased activities on mixed micelles of bile salt with egg phosphatidylcholine, depending on the composition of the micelles. This activation is consistent with previous protein-engineering studies of pig pancreatic phospholipase A2. In this study, we present new information concerning the specificity and interfacial recognition behaviour of this enzyme in relation to this activation.