ACYL-CHAIN SELECTIVITY OF THE 85-KDA PHOSPHOLIPASE-A(2) AND OF THE RELEASE PROCESS IN INTACT MACROPHAGES

The selectivity of the intracellular 85 kDa phospholipase A(2) (PLA(2) -85) towards fatty acids closely related to arachidonic acid has been investigated, using purified PLA(2)-85 from J774 cells and mixed phosp holipids, dually acyl-chain-labelled in the sn-2 position. In parallel experiments, we assessed the acyl-chain selectivity of the release pr ocess in intact, dually labelled, peritoneal mouse macrophages respond ing to either calcium ionophore or zymosan beads in the presence of in domethacin and BSA. The results obtained in the two systems were very similar, which supports previous evidence that PLA(2)-85 is responsibl e for stimulus-induced release of eicosanoid precursor in mouse macrop hages. In the in vitro system, PLA(2)-85 was found to exhibit a modera te selectivity towards C-20 acyl chains differing in double-bond struc ture, while the sensitivity to acyl-chain length was more pronounced. Together with previous data, these results demonstrate a striking pref erence for C-20 over either C-18 or C-22 unsaturated acyl chains.