Group IVA cytosolic phospholipase A2; catalytic domain; Ca-dependent
Group IVA cPLA2, an 85 kDa protein, consists of two domains: the regulatory C2 domain and the alpha/beta hydrolase PLA2 domain. Group IVA cPLA2 is also referred to as cPLA2-alpha. The catalytic domain of cytosolic phospholipase A2 (cPLA2; EC 220.127.116.11) 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. A calcium-dependent phospholipid binding domain resides in the N-terminal region of cPLA2; it is homologous to the C2 domain superfamily which is not included in this hierarchy. Includes PLA2G4A from chicken, human, and frog.