Cloning and characterization of novel rat and mouse low molecular weight Ca(2+)-dependent phospholipase A2s containing 16 cysteines.

A novel rat 4.4-kilobase (kb) cDNA encoding a low molecular weight Ca(2+)-dependent phospholipase A2 (PLA2) and its murine homologue were cloned. The rat and mouse cDNA predict a mature protein of 130 amino acids (M(r) = 14, 763) preceded by a 28-amino acid prepro-peptide. The deduced amino acid sequences encode a protein containing 16 cysteines which distinguishes them from both mammalian group I and II PLA2s and the recently described group of mammalian PLA2s containing 12 cysteines. A rat RNA blot hybridized with the rat cDNA exhibited an abundant 2.3-kb and a less abundant 5-kb transcript in testis. When the rat cDNA was expressed using an Epstein-Barr virus-based vector in human 293s cells, PLA2 activity accumulated in the culture medium. Conditioned medium optimally hydrolyzed the phospholipids of [1-14C]oleate-labeled Escherichia coli at neutral to alkaline pH with 1-7 mM Ca2+. In assays with individual substrates, L-alpha-1-stearoyl-2-arachidonyl phosphatidylinositol was hydrolyzed more efficiently than L-alpha-1-palmitoyl-2-oleoyl phosphatidylcholine, L-alpha-1-palmitoyl-2-arachidonyl phosphatidylcholine, or L-alpha-1-palmitoyl-2-arachidonyl phosphatidylethanolamine.