Hydrolyzes glycerol-phospholipids at the terminal phosphodiesteric bond. Plays an important role in various cellular processes. a 1,2-diacyl-sn-glycero-3-phosphocholine + H2O = a 1,2-diacyl-sn-glycero-3-phosphate + choline + H(+) Optimum pH is 6.0. Stable from 4 to 37 degrees Celsius. Activity is reduced to one third of the original level after incubation at 50 degrees Celsius for 30 minutes. Monomer. Expressed in leaves, roots, developing seeds and cultured cells. The transcript begins to emerged in seeds as early as the second day after imbibition and increased after radicle emergence on the third day. Strongly expressed in the leaves, roots and residual grain of seedling eight days after imbibition. Undetectable in mature dry seeds. C2 domain is a calcium-binding fold, and the binding promotes the protein association with membranes. A lower affinity toward calcium can be anticipated for PLD alpha due to the absence of two potential calcium ligands. Belongs to the phospholipase D family. C2-PLD subfamily.