Phospholipase A2 homolog

General Catalytically inactive snake venom phospholipases A2 (svPLA2s) present a high degree of amino acid sequence similarity to viperid snake PLA2s (group II subfamily). In these PLA2 variants, the aspartic acid residue at position 49 (Asp49) that is invariable in catalytically active PLA2s, is substituted by a lysine residue (Lys49). The epsilon-amino group of the Lys49 is located in the position normally occupied by the Ca 2+ cofactor in the Asp49-PLA2, and Lys49-PLA2s are catalytically inactive partly as a consequence of the loss Ca 2+ cofactor binding.

Although the Lys49-PLA2s do not show catalytic activity, they have a Ca 2+-independent membrane-damaging activity that does not involve the hydrolysis of membrane phospholipids. Nevertheless, the in vivo activities of the Lys49-PLA2s include the formation of edema and local myonecrosis, cytolysis of a wide range of cell types, bactericidal activity and local inflammation and pain.