Endogenous phospholipase A(2) inhibitors in snakes: a brief overview

The blood plasma of numerous snake species naturally comprises endogenous phospholipase A(2) inhibitors, which primarily neutralize toxic phospholipases A(2) that may eventually reach their circulation. This inhibitor type is generally known as snake blood phospholipase A(2) inhibitors (sbPLIs). Most, if not all sbPLIs are oligomeric glycosylated proteins, although the carbohydrate moiety may not be essential for PLA(2) inhibition in every case. The presently known sbPLIs belong to one of three structural classes – namely sbαPLI, sbβPLI or sbγPLI – depending on the presence of characteristic C-type lectin-like domains, leucine-rich repeats or three-finger motifs, respectively. Currently, the most numerous inhibitors described in the literature are sbαPLIs and sbγPLIs, whereas sbβPLIs are rare. When the target PLA(2) is a Lys49 homolog or an Asp49 myotoxin, the sbPLI is denominated a myotoxin inhibitor protein (MIP). In this brief overview, the most relevant data on sbPLIs will be presented. Representative examples of sbαPLIs and sbγPLIs from two Old World – Gloydius brevicaudus and Malayopython reticulatus – and two New World – Bothrops alternatus and Crotalus durissus terrificus – snake species will be emphasized.