SVSPs

Snake venom serine proteases, abbreviated as SVSPs, are a diverse family of single-chain serine proteases found in the venoms of many snakes, especially viperids and some elapids. They are primarily involved in prey immobilization and digestion through disruption of blood coagulation and hemostasis. SVSPs can act as thrombin-like enzymes that cleave fibrinogen to form fibrin, or as activators and modulators of other coagulation factors, leading to procoagulant or anticoagulant effects. The net result in envenomation is often a complex pattern of bleeding, clotting abnormalities, and sometimes systemic coagulopathy.

In terms of structure, SVSPs share the canonical chymotrypsin-like fold characteristic of serine proteases. They are typically around 20–30 kDa in molecular weight and are produced as inactive zymogens that become active upon processing. The catalytic triad—histidine, aspartate, and serine—drives peptide bond cleavage, with substrate specificity largely determined by the residues lining the S1 pocket. The diversity of SVSPs reflects variations in substrate preference and regulatory interactions, allowing different toxins to target distinct points in the coagulation cascade.

Biological activity varies among SVSPs. Some act as procoagulants by activating coagulation factors or by converting fibrinogen into cross-linked fibrin, while others act fibrinogenolytically, degrading fibrinogen and causing defibrination. Other SVSPs modulate platelets or participate in kallikrein-kinin pathways, contributing to hypotension or inflammation. The mixture of activities produced by a snake venom can complicate clinical presentations and is countered clinically with antivenoms and supportive care.

SVSPs are studied to understand hemostasis and venom evolution, and their properties inspire research into potential therapeutic approaches for thrombosis and coagulation disorders, though their use is limited by safety concerns and the complexity of venom.