Continuous spectrophotometric assay of phospholipase A2 activity hydrolyzing plasmalogens using coupling enzymes.

We developed a continuous spectrophotometric assay of the phospholipase A2 activity specific for choline plasmalogen using rat liver lysoplasmalogenase and horse liver alcohol dehydrogenase as coupling enzymes and Naja naja venom phospholipase A2 as a source of the phospholipase A2 activity. In these coupling reactions, choline lysoplasmalogen is hydrolyzed by lysoplasmalogenase to glycerophosphocholine and free aldehyde. The free aldehyde is quantitatively converted to alcohol by alcohol dehydrogenase with the oxidation of NADH. The disappearance of NADH is measured spectrophotometrically at 340 nm. The assay is sensitive to about 0.2 nmol aldehyde produced/ml/min and also is rapid, convenient, and continuous.