Residue Asn21 acts as a switch for calcium binding to modulate the enzymatic activity of human phospholipase A2 group IIE.

Secreted phospholipases A2 (sPLA2) group IIE (GIIE) is involved in several biological events, such as lipid metabolism and possibly inflammation that may mainly depend on its catalytic reaction. We previously showed that Asn21 is a critical residue that contributes to the enzymatic activity of hGIIE, but the underlying mechanism is still not clear. Here, combined with crystal structures and mutagenesis studies of the Asn21Gly mutant, we demonstrate that Asn21 acts as a switch responsible for the calcium binding and the catalytic efficiency. Our results of the atypical feature of calcium binding in hGIIE not only provide clues to understand the molecular basis of its enzymatic activity and physiological function, but also confer improved specificity for potential inhibitor design of sPLA2.

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