Antiflammin-2 (HDMNKVLDL) does not inhibit phospholipase A2 activities

A basic nonapeptide P2 (antiflammin-2, HDMNKVLDL) which is identical to a portion of the amino acid sequence (residues 246-254) of lipocortin I, has been described to have antiinflammatory activity in a rat paw edema model (Nature 335: 726-730 [1988]). P2 (0.05 microM) was also reported to inhibit porcine pancreatic phospholipase A2 (PLA2). The effect of synthetic P2 (98% pure) on PLA2 was evaluated in two assay systems. Using porcine pancreatic PLA2 and phosphatidylcholine/deoxycholate mixed micellar substrate, P2 (0.005-50 microM) had no effect on PLA2 activity, even in the presence of 2-mercaptoethanol to prevent peptide oxidation. In another assay, using human synovial fluid PLA2 as the enzyme and [14C]-oleate-labelled E. coli substrate, P2 (0.005-50 microM) had no significant effect on PLA2 activity. A reported PLA2 inhibitor, manoalide, was a potent inhibitor of PLA2 in both assay systems. On the basis of these results, we conclude that P2 is devoid of PLA2 inhibitory activity.