Functional characteristics of a phospholipase A(2) inhibitor from Notechisater serum

A phospholipase A(2) inhibitor has been purified from the serum of Notechis ater using DEAE-Sephacel chromatography. The inhibitor was found to be com posed of two protein subunits (alpha and beta) that form the intact complex of approximately 110 kDa. The alpha-chain is a 30-kDa glycoprotein and the beta-chain a nonglycosylated, 25-kDa protein. N-terminal sequence analysis reveals a high level of homology to other snake phospholipase A(2) inhibit ors. The inhibitor was shown to be extremely pH and temperature stable. The inhibitor was tested against a wide variety of phospholipase A(2) enzymes and inhibited the enzymatic activity of all phospholipase A(2) enzymes test ed, binding with micromole to nanomole affinity. Furthermore, the inhibitor was compared with the Eli-Lilly compound LY311727 and found to have a high er affinity for human secretory nonpancreatic phospholipase A(2) than this chemical inhibitor. The role of the carbohydrate moiety was investigated an d found not to affect the in vitro function of the inhibitor.