Binding mode of phospholipase A2 with a new type of phospholipid analog having an oxazolidinone ring.

Inhibition of phospholipases A2 (PLA2s) by a new type of monodispersed phospholipid analog, 3-dodecanoyl-4-phosphatidylcholinohydroxymethyl-2-oxazolidinone (oxazolidinone-PC), was investigated by the pH stat assay method using monodispersed 1,2-dihexanoyl-sn-glycero-3-phosphorylcholine (diC6PC) as the substrate. The PLA2s used were those from bovine pancreas and cobra (Naja naja atra) venom (Group I) and from Japanese mamushi (Agkistrodon halys blomhoffii) venom (Group II). This new-type substrate analog was shown to inhibit competitively both types of venom and bovine pancreatic enzymes by binding to the active site in a similar manner to the carboxamide-type analog 2-dodecanoyl-amino-1-hexanol-phosphocholine (amide-PC). The binding of a stereoisomer, (R)-amide-PC, to N. naja atra (Group I) and A. halys blomhoffii (Group II) PLA2s was facilitated by the binding of Ca2+ to the enzymes. On the other hand, the binding of (R)-oxazolidinone-PC to the N. naja atra (Group I) enzyme was found to be independent of Ca2+ binding, while its binding to the A. halys blomhoffii (Group II) enzyme was markedly facilitated by the binding of Ca2+ to the enzyme. The binding of (R)-amide-PC to N. naja atra PLA2 (Group I) was markedly influenced by the ionization state of the catalytic residue His 48, whereas the binding of (R)-oxazolidinone-PC was found to be practically independent of the ionization state of this residue.(ABSTRACT TRUNCATED AT 250 WORDS)