A novel intracellular membrane-bound calcium-independent phospholipase A₂

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 A₂ (iPLA₂). When expressed in COS-7 cells, the protein predominantly exists in the membrane fraction and exhibits a phospholipase A₂ activity in a calcium-independent manner. The transcript of the membrane-bound iPLA₂ 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 iPLA₂ catalytic region. Thus the novel type of iPLA₂ is evolutionarily well conserved, suggestive of its biological significance. (C) 2000 Academic Press.