Primary structures and partial toxicological characterization of two phospholipases A from Micrurus mipartitus and Micrurus dumerilii coral snake venoms.

Snake venom phospholipases A (PLA) share high sequence identities and a conserved structural scaffold, but show important functional differences. Only a few PLAs have been purified and characterized from coral snake (Micrurus spp.) venoms, and their role in envenomation remains largely unknown. In this report, we describe the isolation, sequencing and partial functional characterization of two Micrurus PLAs: MmipPLA from Micrurus mipartitus and MdumPLA from Micrurus dumerilii, two species of clinical importance in Colombia. MmipPLA consisted of 119 amino acid residues with a predicted pI of 8.4, whereas MdumPLA consisted of 117 residues with a pI of 5.6. Both PLAs showed the conserved 'group I' cysteine pattern and were enzymatically active, although MdumPLA had higher activity. The two enzymes differed notably in their toxicity, with MmipPLA being highly lethal to mice and mildly myotoxic, whereas MdumPLA was not lethal (up to 3 μg/g body weight) but strongly myotoxic. MdumPLA displayed higher anticoagulant activity than MmipPLAin vitro and caused more sustained edema in the mouse footpad assay. Neither of these enzymes was cytolytic to cultured skeletal muscle C2C12 myotubes. Based on their structural differences, the two enzymes were placed in separate lineages in a partial phylogeny of Micrurus venom PLAs and this classification agreed with their divergent biological activities. Overall, these findings highlight the structural and functional diversity of Micrurus venom PLAs.