Lipomodulin, a naturally occurring phospholipase A₂ inhibitory protein

Abstract

Phospholipase A₂ is an enzyme that cleaves an acyl group in the 2-position of the glycerol moiety of phospholipids. This acyl group is generally a polyunsaturated fatty acid, and is often found to be arachidonic acid, a precursor of prostaglandins and leukotrienes (Van Den Bosh, 1980). The latter compounds are well known to have diverse biological actions such as inflammation, pain, fever and so on (Kuehl & Egan, 1980). Lysophosphatidylcholine, the other product from phosphatidylcholine, also has a variety of biological actions, including enhancement of Na⁺ permeability and glucose uptake, and inhibition of adenylate cyclase (Shier, 1982). Thus, both products of phosphatidylcholine by the action of phospholipase A₂, have various effect on biological and physiological functions. Since arachidonic acid is released from the cells responding to physiological and pathological stimuli (Kuehl & Egan, 1980), specific inhibitors for phospholipase A₂ will provide insights to exploit more detailed roles of phospholipase A₂ in many intracellular events.