Polarographic assay for phospholipase A2

A rapid, specific, and quantitative assay for phospholipase A₂ from Naja naja venom has been devised, in which phospholipid hydrolysis is measured as soybean lipoxidase-catalyzed oxygen incorporation into the ensuing unsaturated fatty acids. Under conditions where phospholipid was limiting, a linear relationship developed between the extent of oxygen uptake and the amount of egg lecithin metabolized. When phospholipase was rate limiting, the initial rate of oxygen consumption was a linear function of phospholipase concentration over a 14-fold range from 30 to 420 ng/ml. This linear relationship did not exist at higher phospholipase levels, probably due to the micellar nature of the phospholipid. Since this assay can readily detect as little as 17 ng/ml of phospholipase A₂ (Naja naja venom) and is insensitive to most potential interfering materials, it should be useful in a variety of applications.