Biochemical characterization of a phospholipase A2 homologue from the venom of the social wasp Polybia occidentalis

Rafaela Diniz-Sousa, Anderson M. Kayano, Cleópatra A. Caldeira, Rodrigo Simões-Silva, Marta C. Monteiro, Leandro S. Moreira-Dill, Fernando P. Grabner, Leonardo A. Calderon, Juliana P. Zuliani, Rodrigo G. Stábeli, Andreimar M. Soares

Wasp venoms constitute a molecular reservoir of new pharmacological substances such as peptides and proteins, biological property holders, many of which are yet to be identified. Exploring these sources may lead to the discovery of molecules hitherto unknown. This study describes, for the first time in hymenopteran venoms, the identification of an enzymatically inactive phospholipase A2(PLA2) from the venom of the social waspPolybia occidentalis. P. occidentalis venom was fractioned by molecular exclusion and reverse phase chromatography. For the biochemical characterization of the protein, 1D and 2D SDS-PAGE were performed, along with phospholipase activity assays on synthetic substrates, MALDI-TOF mass spectrometry and sequencing by Edman degradation. The protein, called PocTX, was isolated using two chromatographic steps. Based on the phospholipase activity assay, electrophoresis and mass spectrometry, the protein presented a high degree of purity, with a mass of 13,896.47 Da and a basic pI. After sequencing by the Edman degradation method, it was found that the protein showed a high identity with snake venom PLA2homologues. This is the first report of an enzymatically inactive PLA2isolated from wasp venom, similar to snake PLA2homologues.