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Mammalian secretory phospholipase A 2 s (sPLA 2 s) form a family of structurally related enzymes that are involved in a variety of physiological and pathological processes via the release of arachidonic acid from membrane phospholipids or the binding to specific membrane receptors. Here, we report the cloning and characterization of a novel sPLA 2 that is the sixth isoform of the sPLA 2 family found in humans. The novel human mature sPLA 2 consists of 123 amino acids (M r ‫؍‬ 14,000) and is most similar to group IIA sPLA 2 (sPLA 2 -IIA) with respect to the number and positions of cysteine residues as well as overall identity (51%). Therefore, this novel sPLA 2 should be categorized into group II and called group IIE (sPLA 2 -IIE) following the recently identified group IID sPLA 2 (sPLA 2 -IID). The enzymatic properties of recombinant human sPLA 2 -IIE were almost identical to those of sPLA 2 -IIA and IID in terms of Ca 2؉ requirement, optimal pH, substrate specificity, as well as high susceptibility to the sPLA 2 inhibitor indoxam. Along with the biochemical properties of proteins, genetic and evolutional similarities were also observed among these three types of group II sPLA 2 s as to the chromosomal location of the human gene (1p36) and the exon/intron organization. The expression of sPLA 2 -IIE transcripts in humans was restricted to the brain, heart, lung, and placenta in contrast to broad expression profiles for sPLA 2 -IIA and -IID. In sPLA 2 -IIA-deficient mice, the expression of sPLA 2 -IIE was markedly enhanced in the lung and small intestine upon endotoxin challenge, which contrasted with the reduced expression of sPLA 2 -IID mRNA. In situ hybridization analysis revealed elevation of sPLA 2 -IIE mRNA at alveolar macrophage-like cells in the lung of endotoxin-treated mice. These findings suggest a distinct functional role of novel sPLA 2 -IIE in the progression of inflammatory processes.