Purification, characterization and cytokine release function of a novel Arg-49 phospholipase A2 from the venom of Protobothrops mucrosquamatus

Group IIA phospholipase A2 (PLA2) are major components in Viperidae/Crotalidae venom. In the present study, a novel PLA2 named promutoxin with Arg at the site 49 has been purified from the venom of Protobothrops mucrosquamatus by chromatography. It consists of 122 amino acid residues with a molecular mass of 13,656 Da assessed by MALDI-TOF. It has the structural features of snake venom group IIA PLA2s, but has no PLA2 enzymatic activity. Promutoxin shows higher amino acid sequence identity to the K49 PLA2s (72-95%) than to D49 PLA2s (52-58%). Promutoxin exhibits potent myotoxicity in the animal model with as little as 1 μg of promutoxin causing myonecrosis and myoedema in the gastrocnemius muscle of mice. Promutoxin is also able to stimulate the release of IL-12, TNFα, IL-6 and IL-1β from human monocytes, and induce IL-2, TNFα and IL-6 release from T cells, indicating that this snake venom group IIA PLA2 is actively involved in the inflammatory process in man caused by snake venom poisoning.