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.