LIPASE ACTIVITIES OF P37, THE MAJOR ENVELOPE PROTEIN OF VACCINIA VIRUS

p37, the major protein of the extracellular enveloped form of vaccinia virus, is involved in the biogenesis of the viral double membrane and in egress of virus from the cell, p37 was expressed as a glutathione S-transferase fusion protein and was purified to homogeneity by silver staining using glutathione-agarose, Sephacryl S-200, and DEAE-cellulo se chromatography, Incubation of p37 with phosphatidylcholine labeled in the fatty acyl side chains resulted in the production of multiple l ipid products that were identified by thin layer chromatography and ma ss spectrometry as diacylglycerol, free fatty acid, monoacylglycerol, and lysophosphatidylcholine, Lipid-metabolizing activities colocalized with p37-containing fractions throughout the chromatographic steps, p 37 also metabolized phosphatidylethanolamine efficiently, but it had l ess activity toward phosphatidylinositol and little or no activity tow ard phosphatidylserine, The purified enzyme also metabolized triacylgl ycerol to diacylglycerol but was inactive toward sn-1,2-diacylglycerol . p37 was also expressed in insect cells as a poly-His fusion protein; cell lysates and partially purified proteins also generated products expected from phospholipase C and A activities, Thus, p37 is a broad s pecificity lipase with phospholipase C, phospholipase A, and triacylgl ycerol lipase activities.