CARBODIIMIDE MODIFICATION ENHANCES ACTIVITY OF PIG PANCREATIC PHOSPHOLIPASE A(2)

Pig phospholipase A(2), pig iso-phospholipase A(2) and bovine pancreat ic phospholipase A(2) were reacted in solution with 1-ethyl-3-(3-dimet hylaminopropyl)carbodiimide, in the presence of N-hydroxysulfosuccinim ide, at pH 7. The influence of micellar protectants was analyzed. In t he presence of n-hexadecylphosphocholine, the losses of activity in mi cellar diheptanoyl-lecithin were 80, 35, and 10% in bovine phospholipa se A(2), pig iso-phospholipase A(2), and pig phospholipase A(2), respe ctively. With 1-oleoylglycerophosphocholine, the bovine enzyme lost 40 % activity, but the pig enzyme was activated sevenfold. The modified p ig enzyme showed pre-micellar activation on monomeric diheptanoyl-leci thin, and either reduced or increased activities on mixed micelles of bile salt with egg phosphatidylcholine, depending on the composition o f the micelles. This activation is consistent with previous protein-en gineering studies of pig pancreatic phospholipase A(2). In this study, we present new information concerning the specificity and interfacial recognition behaviour of this enzyme in relation to this activation.