Hydrolysis of phosphatidylcholine with phospholipase A2 (EC 3.1.1.4) and phospholipase A1 (EC 3.1.1.32) activities. a 1,2-diacyl-sn-glycero-3-phosphocholine + H2O = a 2-acyl-sn-glycero-3-phosphocholine + a fatty acid + H(+) a 1,2-diacyl-sn-glycero-3-phosphocholine + H2O = a 1-acyl-sn-glycero-3-phosphocholine + a fatty acid + H(+) Binds 1 Ca(2+) ion per monomer. In the dimeric form the Ca(2+) is bound by different amino acids with binding of each Ca(2+) shared with ligands coming from each monomer. The Ca(2+) ion may have a role in catalysis. Homodimer; dimerization is reversible, and the dimeric form is the active one. One of the very few enzymes located there. Present in outer membrane vesicle formulations which are used as vaccines in human. Belongs to the phospholipase A1 family.