A novel intracellular membrane-bound calcium-independent phospholipase A(2)

We have cloned human cDNA encoding a novel protein of 782 amino acids that contains the lipase consensus sequence Gly-Xaa-Ser-Xaa-Gly and several stretches surrounding the motif, which are homologous to those of the catalytic domain of cytosolic calcium-independent phospholipase A(2) (iPLA(2)). When expressed in COS-7 cells, the protein predominantly exists in the membrane fraction and exhibits a phospholipase A(2) activity in a calcium-independent manner. The transcript of the membrane-bound iPLA(2) gene is ubiquitously observed as a single band of approximately 3.3 kb on Northern blot, with the most abundant expression in the skeletal muscle and heart. By a search of the database, we have also identified its putative C. elegans homologue, which shows 47% identity with that of human in the iPLA(2) catalytic region. Thus the novel type of iPLA(2) is evolutionarily well conserved, suggestive of its biological significance.