A genus-wide study on venom proteome variation and phospholipase A2 inhibition in Asian lance-headed pit vipers (genus: Trimeresurus).

High molecular weight proteins are present abundantly in viper venoms. The amino acid sequence can be highly variable though, contributing to the structure and function diversity of snake venom protein. This, however, remains unresolved in many species. The study investigated the venom protein variability in a distinct clade of Asian pit vipers (Trimeresurus species) through comparative proteomics, applying gel electrophoresis (SDS-PAGE), liquid chromatography-tandem mass spectrometry (LCMS/MS), and bioinformatic approaches. The proteomes revealed a number of conserved protein families, within each are variably expressed protein paralogs that are unrelated to the snake phylogeny and geographic origin. The expression levels of two major enzymes, i.e., snake venom serine proteinase and metalloproteinase, correlate weakly with procoagulant and hemorrhagic activities, implying co-expression of other functionally versatile toxins in the venom. The phospholipase A₂ (PLA₂) abundance correlates strongly with its enzymatic activity, and a unique phenotype was discovered in two species expressing extremely little PLA₂. The commercial mono-specific antivenom effectively neutralized the venoms' procoagulant and hemorrhagic effects but failed to inhibit the PLA₂ activities. Instead, the PLA₂ activities of all venoms were effectively inhibited by the small molecule inhibitor varespladib, suggesting its potential to be repurposed as a highly potent adjuvant therapeutic in snakebite envenoming.