15-LIPOXYGENATION OF PHOSPHOLIPIDS MAY PRECEDE THE SN-2 CLEAVAGE BY PHOSPHOLIPASES A(2) - REACTION SPECIFICITIES OF SECRETORY AND CYTOSOLICPHOSPHOLIPASES A(2) TOWARDS NATIVE AND 15-LIPOXYGENATED ARACHIDONOYL PHOSPHOLIPIDS

Reticulocyte-type 15-lipoxygenase is known to dioxygenate phospholipid s without preceding action of phospholipases A(2) (PLA(2)), Therefore we studied the reaction of the secretory PLA(2)s (sPLA(2)) from pancre as and snake venom, and of the human cytosolic PLA(2) (cPLA(2)) with 1 -palmitoyl-2-arachidonoyl phosphatidylcholine (PAPC) and their 15-lipo xygenated species (PAPC-OOH and PAPC-OH) either alone or as equimolar mixtures. These PLA(2)s cleaved PAPC-O(O)H with higher (sPLA(2)) or si milar rates (cPLA(2)) as compared with native PAPC, In mixtures, howev er, PAPC proved to be the preferred, albeit not exclusive substrate fo r all three PLA(2)s. Thus, partial 15-lipoxygenation of phospholipids may also trigger liberation of arachidonic acid. (C) 1998 Federation o f European Biochemical Societies.