Phospholipase A2 (PLA2) catalyzes the hydrolysis of fatty acids at the sn-2 position of glycerophospholipids, yielding a free fatty acid and a lysophospholipid as products. There are three broad classes of PLA2, secretory (sPLA2), calcium-dependent cytosolic (cPLA2), and calcium-independent cytosolic (iPLA2), that have different functions. FKGK 11 is a selective inhibitor of iPLA2 that demonstrates an XI(50) value of 0.0073, where XI(50) equals the mole fraction of FKGK 11 in the total substrate interface required to inhibit iPLA2 by 50%. In comparison, mole fractions as high as 0.091 do not inhibit cPLA2 activity and cause only slight inhibition of sPLA2.