Differential Hematotoxic Activity of Southeast Asian Pit Viper Venoms: The Cross-Neutralizing Effect of Available Antivenoms

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  Image Credit: Creative Commons (some rights reserved) CC BY-NC Photo 111998430, (c) Nicholas Hess Differential Hematotoxic Activity of Southeast Asian Pit Viper Venoms: The Cross-Neutralizing Effect of Available Antivenoms Abstract Background/Objectives : Pit vipers (subfamily Crotalinae) are responsible for a large proportion of snakebite envenoming cases in Southeast Asia. Envenomation by these snakes commonly causes hematotoxic effects, including platelet dysfunction and coagulation disturbances. Although antivenom remains the mainstay of treatment, species-specific antivenoms are not available for several regional pit viper species. This study evaluated the hematotoxic activities of selected Southeast Asian pit viper venoms and the cross-neutralizing capacity of commercially available antivenoms.  Methods : Venoms from five medically important pit viper species— Calloselasma rhodostoma ,  Trimeresurus albolabris ,  T. hageni ,  T. purpureomaculatus , ...

Crystal structure and functional characterization of an Asp49 phospholipase A2 from the bushmaster (Lachesis muta)

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Image Credit: By Christopher Murray - en:Image:Lachesis muta muta.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=1120263

Crystal structure and functional characterization of an Asp49 phospholipase A2 from the bushmaster (Lachesis muta)

Snake-venom phospholipases A2 (PLA2s) are small, structurally conserved enzymes that contribute significantly to the pathophysiology of envenomation. Here, we report the purification and crystal structure of an Asp49-PLA2 isolated from the venom of Lachesis muta, a pit viper from the Peruvian Amazon. The enzyme was purified using ion-exchange and size-exclusion chromatography and exhibited phospholipase activity in a dose- and time-dependent egg-yolk degradation assay. Pure protein crystals were obtained in space group P6222 and diffracted to 2.36 Å resolution, with two molecules in the asymmetric unit. The structure reveals the canonical fold of catalytically active group II PLA2s, with a bound Ca2+ ion and a MES molecule in the active site of one monomer. Seven disulfide bonds stabilize the structure, although one bridge typically associated with the β-hairpin is absent and is replaced by a salt bridge as in other viperid PLA2s. PISA analysis suggests a potential tetrameric assembly composed of two AB dimers generating an interface between two A subunits (A–A′). Electrostatic surface mapping reveals a notable positively charged channel at the A–A′ interface, like that seen for a basic PLA2 homodimer from Crotalus durissus terrificus in which the two active sites lie accessible to the membrane. This study presents the first structural and enzymatic analysis of an Asp49-PLA2 from L. muta and provides insights into its oligomeric assembly, electrostatic landscape and potential adaptations relevant to its role in venom toxicity.

Neyra Chama, N. E., Romero Vargas, F. F., Condori Mamani, E., Vargas, J. A., Alves Furtado, A., D'Muniz Pereira, H., Navarro Oviedo, R. D., Garratt, R. C., Vega Ramirez, J. L. J. & Leonardo, D. A. (2026). Acta Cryst. F82. https://journals.iucr.org/f/issues/2026/05/00/nq5002/index.html