A novel phospholipase from Trypanosoma brucei

Abstract

Phospholipase A1 activities have been detected in most cells where they have been sought and yet their characterization lags far behind that of the phospholipases A2, C and D. The study presented here details the first cloning and characterization of a cytosolic PLA1 that exhibits preference for phosphatidylcholine (GPCho) substrates. Trypanosoma brucei phospholipase A1 (TbPLA1) is unique from previously identified eukaryotic PLA1 because it is evolutionarily related to bacterial secreted PLA1. A T. brucei ancestor most likely acquired the PLA1 from a horizontal gene transfer of a PLA1 from Sodalis glossinidius, a bacterial endosymbiont of tsetse flies. Nano-electrospray ionization tandem mass spectrometry analysis of TbPLA 1 mutants established that the enzyme functions in vivo to synthesize lysoGPCho metabolites containing long-chain mostly polyunsaturated and highly unsaturated fatty acids. Analysis of purified mutated recombinant forms of TbPLA1 revealed that this enzyme is a serine hydrolase whose catalytic mechanism involves a triad consisting of the amino acid residues Ser-131, His-234 and Asp-183. The TbPLA1 homozygous null mutants generated here constitute the only PLA1 double knockouts from any organism. © 2007 The Authors.