PURIFICATION AND CHARACTERIZATION OF PLATELET-ACTIVATING-FACTOR ACETYLHYDROLASE FROM PERITONEAL-FLUID OBTAINED FROM GUINEA-PIGS AFTER ENDOTOXIN-SHOCK

Platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocho line; PAF) acetylhydrolase is an enzyme that hydrolyzes the acetyl est er of PAF. We purified this enzyme, which accumulated in the peritonea l cavity during endotoxin shock, by ammonium sulfate precipitation, an d sequential use of butyl-Toyopearl, heparin-Sepharose, Con A-Sepharos e, chelating-Sepharose, and MonoQ column chromatographies. We identifi ed a monomeric polypeptide with a molecular weight of approximately 63 kDa on SDS-PAGE. This molecular weight differs from those of previous ly described acetylhydrolases. The purified enzyme did not degrade pho spholipids with a long chain fatty acyl group at the sn-2 position. In addition, the enzyme activity was not inhibited by either pBPB or qui nacrine. Accordingly, this enzyme is distinct from phospholipase A(2). In addition, this enzyme also hydrolyzed some oxidatively fragmented phospholipids with PAF-like biological activities such as -hexadecyl-2 -glutaroyl-sn-glycero-3-phosphocholine and hexadecyl-2-succinoyl-sn-gl ycero-3-phosphocholine.