Toxoplasma gondii secretes a calcium-independent phospholipase A(2)

Phospholipases A(2) (PLA(2)) play an important role in Toxoplasma gondii ho st cell penetration. They are also key enzymes in the host cell response to the parasite invasion. PLA(2) hydrolyse cellular phospholipids, releasing multiple inflammatory lipidic mediators. We have investigated the biochemic al characterisation of T. gondii PLA(2) activity in a mouse-cultured tachyz oite homogenate and in the peritoneal exudate from infected mice, using the hydrolysis of a fluorescent phosphatidylglycerol labelled at the sn-2 posi tion. Spectrofluorimetry and thin-layer chromatography showed a PLA(2) acti vity (about 0.5-2 nmol/min per mg), calcium-independent, secreted into infe cted mice peritoneal exudate, with a broad pH activity ranging between 6.5 and 9.5 and resistant to a great number of potential PLA(2) inhibitors exce pt dithio-nitrobenzoic acid (1 mM). An associated phospholipase A(1) activi ty was also displayed. These results suggest that Toxoplasma gondii display s specific phospholipases different from host enzymes and probably involved at critical steps of infections cycle. (C) 2000 Australian Society for Par asitology Inc. Published by Elsevier Science Ltd. All rights reserved.