Characterization of Arabidopsis secretory phospholipase A2-γ cDNA and its enzymatic properties1

Plant secretory phospholipases A2 (sPLA2s) prob- ably play important roles in phospholipid signaling based on the data reported from other organisms, but their functions are poorly understood because of the lack of cloned sPLA2 genes. In this study, we cloned and characterized an Arabidopsis secretory phospholipase A2-Q (AtsPLA2-Q) cDNA, and exam- ined its enzymatic properties. The recombinant protein of AtsPLA2-Q showed maximal enzyme activity at pH 8.0, and required Ca 2þ for activity. Moreover, AtsPLA2-Q showed sn-2 position speci¢city but no prominent acyl preference, though it showed head group speci¢city to phosphatidylethanolamine rather than to phosphatidylcholine. AtsPLA2-Q was found to predominate in the mature £ower rather than in other tissues, and subcellular localization analysis con¢rmed that AtsPLA2-Q Q