Detection and characterization of extracellular phospholipase A2 in pleural effusion of patients with tuberculosis

Abstract Extracellular phospholipase A 2 activity has been identified in pleural fluid of patients with tuberculosis. This enzyme is a calcium requiring protein and has a pH optimum of 10.0. The enzyme was inhibited by the active site-directed histidine reagent, ϱ-bromophenacyl bromide. Ionic and non-ionic detergents, or the sulfhydryl reagent dithiothreitol, caused loss of enzyme activity. When substrate specificity was tested using 2-[1- 14 C]linoleoyl phospholipids as substrates, phosphatidyl-ethanolamine was the best substrate, followed by phosphatidylserine and phosphatidylcholine. This phospholipase A 2 showed high affinity for heparin, and was recognized by a monoclonal antibody raised against phospholipase A 2 from human synovial fluid. These findings suggest that an extracellular phospholipase A 2 , which may belong to the 14K group II phospholipase A 2 family, exists in the pleural fluid of patients with tuberculosis.