Phosphatidylethanolamine as an exclusive substrate for an original phospholipase D from Dechloromonas

Phospholipases D (PLDs) are lipolytic enzymes that catalyze hydrolysis of the distal phosphodiester bond of various membrane phospholipids (PLs). These enzymes generate invariant phosphatidic acid (PA) and a polar head group whose nature depends on the PL substrate. PA is both a key metabolic intermediate in the synthesis of lipids and a second messenger involved in diverse processes, including cellular signaling, development of cancer in mammals, bacterial pathogenesis, and defense responses in plants. Regarding the diversity of PL nature and composition, all PLDs described so far can act on several PLs. Furthermore, the molecular determinants of PL recognition by PLDs and the preference of one PL over another remain poorly understood. We previously described the biochemical characterization of a PLD, called DaPLD1, from the bacterium Dechloromonas aromatica RCB. This PLD did indeed have a strong preference for phosphatidylethanolamine (PE) over all other PLs but was also able to hydrolyze phosphatidylcholine (PC). Here, we identified a second PLD called DaPLD2, which shares only 38% peptide identity with DaPLD1. We have recombinantly expressed this PLD in Escherichia coli and characterized it biochemically. Unlike DaPLD1, DaPLD2 exhibits an exclusive specificity for PE and is inactive toward other PLs, including PC. DaPLD2 is distant phylogenetically from DaPLD1 but shares common features and key residues found in bacterial PLDs. Altogether, this unique property of DaPLD2 towards PE provides valuable insights into PL metabolism in bacteria and holds potential for development as a tool enzyme to selectively transform PE among other PLs.