Catalytic domain of cytosolic phospholipase A2 (PLA2; EC 126.96.36.199) hydrolyzes the sn-2-acyl ester bond of phospholipids to release arachidonic acid. At the active site, cPLA2 contains a serine nucleophile through which the catalytic mechanism is initiated. The active site is partially covered by a solvent-accessible flexible lid. cPLA2 displays interfacial activation as it exists in both "closed lid" and "open lid" forms. Movement of the cPLA2 lid possibly exposes a greater hydrophobic surface and the active site. cPLA2 belongs to the alpha-beta hydrolase family which is identified by a characteristic nucleophile elbow with a consensus sequence of Sm-X-Nu-Sm (Sm = small residue, X = any residue and Nu = nucleophile). Calcium is required for cPLA2 to bind with membranes or phospholipids. Group IV cPLA2 includes six intercellular enzymes: cPLA2alpha, cPLA2beta, cPLA2gamma, cPLA2delta, cPLA2epsilon, and cPLA2zeta.