Purification and characterization of bothrombin, a fibrinogen-clotting serine protease from the venom of Bothrops jararaca

Understanding the effects of Bothrops erythromelas and Bothrops leucurus venoms on human blood coagulation

Coagulation disorders are a primary symptom of envenomation caused by snakes belonging to the genus Bothrops. In the Northeast region of Brazil, the species Bothrops erythromelas and Bothrops leucurus are the main responsible for snakebite accidents. Due to the specific action of Bothrops venoms on several components of the coagulation cascade, the objective of this work was to characterize the coagulotoxic profile of B. erythromelas and B. leucurus venoms and the neutralizing potential of bothropic antivenom, considering that their venom are not used in the production of antivenom. Regarding the clotting components targeted by the venom of these species, B. leucurus samples had higher thrombin-like activity and ability to activate prothrombin, while the activation of Factor X was comparable between these two species. B.erythromelas and B. leucurus venom displayed α- and β-fibrinogenolytic activities, with the former presenting higher overall fibrinogenolytic activity. In contrast, B. erythromelas venom showed greater procoagulant activity on human plasma, assessed through the coagulation time induced by the venom samples and thromboelastometry. Bothropic antivenom inhibited the procoagulant potential of B. leucurus venom better than B. erythromelas. However, the ability of the antivenom to neutralize this activity is lower compared to that determined for the venom of B. jararaca, which is used for antivenom production. The results shown herein describe the procoagulant activity of B. leucurus and B. erythromelas venoms and highlight the differences regarding their procoagulant capacity on human plasma, contributing to a deeper understanding of the pathophysiology of the envenomation caused by these species.

The Versatility of Serine Proteases from Brazilian Bothrops Venom: Their Roles in Snakebites and Drug Discovery

Serine proteases are multifunctional and versatile venom components found in viper snakes, including the Bothrops species, a widely distributed genus notorious for causing the highest number of snakebites across Latin America. These enzymes, representing a significant fraction of Bothrops venom proteomes, exhibit a wide range of biological activities that influence blood coagulation, fibrinolysis, and inflammation. This review provides a comprehensive overview of serine proteases, with a particular focus on those found in the venom of Brazilian Bothrops snakes. The discussion begins with a summary of snake species found in Brazil and their medical relevance. Specifically addressing the Bothrops genus, this review explores the distribution of these species across Brazilian territory and their associated medical importance. Subsequently, the article investigates the biochemistry of Bothrops venoms and the clinical manifestations induced by envenomation. Finally, it offers an in-depth discussion on the serine proteases, highlighting their biochemical properties, mechanisms of action, and potential therapeutic applications. Furthermore, this review provides an in-depth exploration of the diverse serine proteases found in Bothrops venoms and their functional significance, from thrombin-like effects to potent fibrinogenolytic actions, which determine the clinical manifestations of envenomation. This review delves into the evolutionary adaptations and biochemical diversity of serine proteases in Bothrops venoms, emphasizing their critical roles in venom functionality and the resulting pathophysiological effects. Additionally, it opens new avenues for utilizing these enzymes in biomedical applications, underscoring their potential beyond toxinology.

Exploring the Diversity and Function of Serine Proteases in Toxicofera Reptile Venoms: A Comprehensive Overview

Toxicofera reptile venoms are composed of several toxins, including serine proteases. These proteases are glycosylated enzymes that affect the prey's hemostatic system. Their actions extend across the coagulation cascade, the kallikrein-kinin system, and platelet activation. Despite their specificity for different substrates, these enzymes are homologous across all toxicoferans and display high sequence similarity. The aim of this review is to compile decades of knowledge about venom serine proteases, showing the diversity of biochemically and biophysically characterized enzymes, their structural characteristics, advances in understanding their origin and evolution, as well as methods of obtaining enzymes and their biotechnological applications.

The Clot Thickens: Differential Coagulotoxic and Cardiotoxic Activities of Anguimorpha Lizard Venoms

Despite their evolutionary novelty, lizard venoms are much less studied in comparison to the intense research on snake venoms. While the venoms of helodermatid lizards have long been assumed to be for defensive purposes, there is increasing evidence of toxic activities more useful for predation than defence (such as paralytic neurotoxicity). This study aimed to ascertain the effects of Heloderma, Lanthanotus, and Varanus lizard venoms on the coagulation and cardiovascular systems. Anticoagulant toxicity was demonstrated for the Varanus species studied, with the venoms prolonging clotting times in human and bird plasma due to the destructive cleavage of fibrinogen. In contrast, thromboelastographic analyses on human and bird plasmas in this study demonstrated a procoagulant bioactivity for Heloderma venoms. A previous study on Heloderma venom using factor-depleted plasmas as a proxy model suggested a procoagulant factor was present that activated either Factor XI or Factor XII, but could not ascertain the precise target. Our activation studies using purified zymogens confirmed FXII activation. Comparisons of neonate and adult H. exasperatum, revealed the neonates to be more potent in the ability to activate FXII, being more similar to the venom of the smaller species H. suspectum than the adult H. exasperatum. This suggests potent FXII activation a basal trait in the genus, present in the small bodied last common ancestor. This also indicates an ontogenetic difference in prey preferences in the larger Heloderma species paralleing the change in venom biochemistry. In addition, as birds lack Factor XII, the ability to clot avian plasma suggested an additional procoagulant site of action, which was revealed to be the activation of Factor VII, with H. horridum being the most potent. This study also examined the effects upon the cardiovascular system, including the liberation of kinins from kininogen, which contributes to hypotension induction. This form of toxicity was previously described for Heloderma venoms, and was revealed in this study was to also be a pathophysiological effect of Lanthanotus and Varanus venoms. This suggests that this toxic activity was present in the venom of the last common ancestor of the anguimorph lizards, which is consistent with kallikrein enzymes being a shared toxin trait. This study therefore uncovered novel actions of anguimorph lizard venoms, not only contributing to the evolutionary biology body of knowledge but also revealing novel activities to mine for drug design lead compounds.

Evaluation of the Inhibitory Potential of Synthetic Peptides Homologous to CDR3 Regions of a Monoclonal Antibody against Bothropic Venom Serine Proteases

Snakebite accidents, neglected tropical diseases per the WHO, pose a significant public health threat due to their severity and frequency. Envenomation by Bothrops genus snakes leads to severe manifestations due to proteolytic enzymes. While the antibothropic serum produced by the Butantan Institute saves lives, its efficacy is limited as it fails to neutralize certain serine proteases. Hence, developing new-generation antivenoms, like monoclonal antibodies, is crucial. This study aimed to explore the inhibitory potential of synthetic peptides homologous to the CDR3 regions of a monoclonal antibody targeting a snake venom thrombin-like enzyme (SVTLE) from B. atrox venom. Five synthetic peptides were studied, all stable against hydrolysis by venoms and serine proteases. Impressively, four peptides demonstrated uncompetitive SVTLE inhibition, with Ki values ranging from 10-6 to 10-7 M. These findings underscore the potential of short peptides homologous to CDR3 regions in blocking snake venom toxins, suggesting their promise as the basis for new-generation antivenoms. Thus, this study offers potential advancements in combatting snakebites, addressing a critical public health challenge in tropical and subtropical regions.

Crosstalk of Inflammation and Coagulation in Bothrops Snakebite Envenoming: Endogenous Signaling Pathways and Pathophysiology

Snakebite envenoming represents a major health problem in tropical and subtropical countries. Considering the elevated number of accidents and high morbidity and mortality rates, the World Health Organization reclassified this disease to category A of neglected diseases. In Latin America, Bothrops genus snakes are mainly responsible for snakebites in humans, whose pathophysiology is characterized by local and systemic inflammatory and degradative processes, triggering prothrombotic and hemorrhagic events, which lead to various complications, organ damage, tissue loss, amputations, and death. The activation of the multicellular blood system, hemostatic alterations, and activation of the inflammatory response are all well-documented in Bothrops envenomings. However, the interface between inflammation and coagulation is still a neglected issue in the toxinology field. Thromboinflammatory pathways can play a significant role in some of the major complications of snakebite envenoming, such as stroke, venous thromboembolism, and acute kidney injury. In addition to exacerbating inflammation and cell interactions that trigger vaso-occlusion, ischemia-reperfusion processes, and, eventually, organic damage and necrosis. In this review, we discuss the role of inflammatory pathways in modulating coagulation and inducing platelet and leukocyte activation, as well as the inflammatory production mediators and induction of innate immune responses, among other mechanisms that are altered by Bothrops venoms.

Increased Binding of von Willebrand Factor to Sub-Endothelial Collagen May Facilitate Thrombotic Events Complicating Bothrops lanceolatus Envenomation in Humans

Consumption coagulopathy and hemorrhagic syndrome exacerbated by blood anticoagulability remain the most important causes of lethality associated with Bothrops snake envenomation. Bothrops venom also engages platelet aggregation on the injured endothelium via von Willebrand factor (vWF) interactions. Besides platelet aggregation, some Bothrops venom toxins may induce qualitative thrombopathy, which has been in part related to the inhibition of vWF activation. We tested whether B. lanceolatus venom impaired vWF to collagen(s) binding (vWF:CB) activity. Experiments were performed with B. lanceolatus crude venom, in the presence or absence of Bothrofav, a monospecific B. lanceolatus antivenom. Venom of B. lanceolatus fully inhibited vWF to collagen type I and III binding, suggesting venom interactions with the vWF A3 domain. In contrast, B. lanceolatus venom increased vWF to collagen type VI binding, suggesting the enhancement of vWF binding to collagen at the vWF A1 domain. Hence, B. lanceolatus venom exhibited contrasting in vitro effects in terms of the adhesive properties of vWF to collagen. On the other hand, the antivenom Bothrofav reversed the inhibitory effects of B. lanceolatus venom on vWF collagen binding activity. In light of the respective distribution of collagen type III and collagen type VI in perivascular connective tissue and the sub-endothelium, a putative association between an increase in vWF:CB activity for collagen type VI and the onset of thrombotic events in human B. lanceolatus envenomation might be considered.

Toxic Habits: An Analysis of General Trends and Biases in Snake Venom Research

Biases in snake venom research have been partially identified but seldomly quantified. Using the Google Scholar web search engine, we collected a total of 267 articles published between 1964 and 2021, and reviewed them to assess the main trends in this field of study. We developed a 4-category classification of the harmful potential of each of the 298 snake species retrieved from the analysed publications, and tested whether taxonomy, realm of origin, and/or assigned hazard category could affect how often each of them appeared in the articles considered. Overall, viperids were significantly more represented than any other snake taxon retrieved. The Neotropics were the most represented biogeographic realm for number of studied species, whereas information about the country of origin of the analysed specimens was often incomplete. The vast majority of the publications focused on snake venom characterisation, whereas more ecology-related topics were rarely considered. Hazard category and biogeographic realm of origin of each species had a significant effect on the number of articles dedicated to it, suggesting that a snake's harmful potential and place of origin influence its popularity in venom studies. Our analysis showed an overall positive trend in the number of snake venom studies published yearly, but also underlined severe neglect of snake families of supposedly minor medical relevance (e.g., Atractaspididae), underrepresentation of some of the areas most impacted by snakebite (i.e., Indomalayan and Afrotropic realms), and limited interest in the ecological and functional context of snake venom.

Production of a murine mAb against Bothrops alternatus and B. neuwiedi snake venoms and its use to isolate a thrombin-like serine protease fraction

Accidents with snakes from the genus Bothrops represent ~90 % of all snakebites in Brazil. Monoclonal antibodies (mAbs) targeting venom components can be important assets for treating envenoming syndromes, for developing diagnostic tests and for research purposes. Therefore, in this study, we aimed to generate murine mAbs against the antigenic mixture of Bothropic venoms traditionally used as immunogen to produce Bothropic antivenoms in Brazil. ELISA showed that one of the produced mAbs recognizes B. alternatus and B. neuwiedi venoms (mAb anti-Ba/Bn) specifically and Western Blot revealed that this mAb binds to a single protein band of molecular mass of ≈50 kDa. MAb anti-Ba/Bn inhibited the coagulant activity but was unable to neutralize hemorrhagic and phospholipase A2 activities caused by the B. neuwiedi venom. MAb anti-Ba/Bn was immobilized to Sepharose beads and used for immunoaffinity chromatography of B. neuwiedi venom. Proteolytic activity assays indicated that the immunoaffinity-purified fraction (BnF-Bothrops neuwiedi fraction) has a serine protease thrombin-like profile, which was supported by coagulability assays in mice. Bottom-up proteomic analysis confirmed the prevalence of serine proteases in BnF using label-free quantification. In conclusion, this work characterized a mAb with neutralizing properties against B. neuwiedi coagulant activity and demonstrates that immunoaffinity chromatography using mAbs can be a useful technique for purification of bioactive toxic proteins from Bothrops spp. snake venoms.

Bleeding and Thrombosis: Insights into Pathophysiology of Bothrops Venom-Related Hemostasis Disorders

Toxins from Bothrops venoms targeting hemostasis are responsible for a broad range of clinical and biological syndromes including local and systemic bleeding, incoagulability, thrombotic microangiopathy and macrothrombosis. Beyond hemostais disorders, toxins are also involved in the pathogenesis of edema and in most complications such as hypovolemia, cardiovascular collapse, acute kidney injury, myonecrosis, compartmental syndrome and superinfection. These toxins can be classified as enzymatic proteins (snake venom metalloproteinases, snake venom serine proteases, phospholipases A₂ and L-amino acid oxidases) and non-enzymatic proteins (desintegrins and C-type lectin proteins). Bleeding is due to a multifocal toxicity targeting vessels, platelets and coagulation factors. Vessel damage due to the degradation of basement membrane and the subsequent disruption of endothelial cell integrity under hydrostatic pressure and tangential shear stress is primarily responsible for bleeding. Hemorrhage is promoted by thrombocytopenia, platelet hypoaggregation, consumption coagulopathy and fibrin(ogen)olysis. Onset of thrombotic microangiopathy is probably due to the switch of endothelium to a prothrombotic phenotype with overexpression of tissue factor and other pro-aggregating biomarkers in association with activation of platelets and coagulation. Thrombosis involving large-caliber vessels in B. lanceolatus envenomation remains a unique entity, which exact pathophysiology remains poorly understood.

Snake Venoms in Diagnostic Hemostasis and Thrombosis

Snake venoms have evolved primarily to immobilize and kill prey, and consequently, they contain some of the most potent natural toxins. Part of that armory is a range of hemotoxic components that affect every area of hemostasis, which we have harnessed to great effect in the study and diagnosis of hemostatic disorders. The most widely used are those that affect coagulation, such as thrombin-like enzymes unaffected by heparin and direct thrombin inhibitors, which can help confirm or dispute their presence in plasma. The liquid gold of coagulation activators is Russell's viper venom, since it contains activators of factor X and factor V. It is used in a range of clotting-based assays, such as assessment of factor X and factor V deficiencies, protein C and protein S deficiencies, activated protein C resistance, and probably the most important test for lupus anticoagulants, the dilute Russell's viper venom time. Activators of prothrombin, such as oscutarin C from Coastal Taipan venom and ecarin from saw-scaled viper venom, are employed in prothrombin activity assays and lupus anticoagulant detection, and ecarin has a valuable role in quantitative assays of direct thrombin inhibitors. Snake venoms affecting primary hemostasis include botrocetin from the jararaca, which can be used to assay von Willebrand factor activity, and convulxin from the cascavel, which can be used to detect deficiency of the platelet collagen receptor, glycoprotein VI. This article takes the reader to every area of the diagnostic hemostasis laboratory to appreciate the myriad applications of snake venoms available in diagnostic practice.

Design, synthesis, and evaluation of Bothrops venom serine protease peptidic inhibitors

Background:

In Central and South America, snakebite envenomation is mainly caused by Bothrops spp. snakes, whose venoms feature significant biochemical richness, including serine proteases. The available bothropic antivenoms are efficient in avoiding fatalities, but do not completely neutralize venom serine proteases, which are co-responsible for some disorders observed during envenomation.

Methods:

In order to search for tools to improve the antivenom’s, 6-mer peptides were designed based on a specific substrate for Bothrops jararaca venom serine proteases, and then synthesized, with the intention to selectively inhibit these enzymes.

Results:

Using batroxobin as a snake venom serine protease model, two structurally similar inhibitor peptides were identified. When tested on B. jararaca venom, one of the new inhibitors displayed a good potential to inhibit the activity of the venom serine proteases. These inhibitors do not affect human serine proteases as human factor Xa and thrombin, due to their selectivity.

Conclusion:

Our study identified two small peptides able to inhibit bothropic serine proteases, but not human ones, can be used as tools to enhance knowledge of the venom composition and function. Moreover, one promising peptide (pepC) was identified that can be explored in the search for improving Bothrops spp. envenomation treatment.

High throughput screening and identification of coagulopathic snake venom proteins and peptides using nanofractionation and proteomics approaches

Snakebite is a neglected tropical disease that results in a variety of systemic and local pathologies in envenomed victims and is responsible for around 138,000 deaths every year. Many snake venoms cause severe coagulopathy that makes victims vulnerable to suffering life-threating haemorrhage. The mechanisms of action of coagulopathic snake venom toxins are diverse and can result in both anticoagulant and procoagulant effects. However, because snake venoms consist of a mixture of numerous protein and peptide components, high throughput characterizations of specific target bioactives is challenging. In this study, we applied a combination of analytical and pharmacological methods to identify snake venom toxins from a wide diversity of snake species that perturb coagulation. To do so, we used a high-throughput screening approach consisting of a miniaturised plasma coagulation assay in combination with a venom nanofractionation approach. Twenty snake venoms were first separated using reversed-phase liquid chromatography, and a post-column split allowed a small fraction to be analyzed with mass spectrometry, while the larger fraction was collected and dispensed onto 384-well plates. After fraction collection, any solvent present in the wells was removed by means of freeze-drying, after which it was possible to perform a plasma coagulation assay in order to detect coagulopathic activity. Our results demonstrate that many snake venoms simultaneously contain both procoagulant and anticoagulant bioactives that contribute to coagulopathy. In-depth identification analysis from seven medically-important venoms, via mass spectrometry and nanoLC-MS/MS, revealed that phospholipase A2 toxins are frequently identified in anticoagulant venom fractions, while serine protease and metalloproteinase toxins are often associated with procoagulant bioactivities. The nanofractionation and proteomics approach applied herein seems likely to be a valuable tool for the rational development of next-generation snakebite treatments by facilitating the rapid identification and fractionation of coagulopathic toxins, thereby enabling specific targeting of these toxins by new therapeutics such as monoclonal antibodies and small molecule inhibitors.

Biochemistry of the Thrombin-Like TLBpic and Its Purification fromBothrops pictus“Jergon de la Costa” (Reptilia: Viperidae)

The venom of snakes is composed of a heterogeneous mixture of simple and complex substances, with inflammation and hyperalgesia being the first symptom caused by the action ofBothropsvenom, generating processes such as leukocyte infiltration, hemorrhage, and the intravascular formation of thrombi. Within the simple substances, we have free amino acids, peptides, nucleotides, carbohydrates, lipids, and biogenic amines (organic molecules) as well as cations and anions (inorganic constituents). Of the ions, we can highlight calcium, which is an important cofactor of some proteolytic enzymes as well as phospholipases A2. And magnesium and zinc are important cofactors of venom metalloproteases. Complex substances are related to proteins and enzymes. Studies related to the total venom of snake present in several organic substances act as pain mediators and are called biogenic amines, such as bradykinin, histamine, 4-hydroxytryptamine,N-methyl-5-hydroxytryptamine,N′-N′-dimethyl-5-hydroxytryptamine, and serotonin. In the present study, a fraction with serinoprotease and coagulant activity has been purified on fibrinogen, called TLBpic, using a cationic ion exchange chromatographic system coupled to an HPLC system. The main characteristic of our protocol is the speed, and the high recovery of the fraction with optimal terms gave result of evidence in the SDS-PAGE gel. The ESI (electrospray ionisation), corresponding to the electrophoresis of proteins in polyacrylamide gels and to their denaturing solubilization in the presence of the SDS ionic detergent, uniting the proteins, breaking hydrophobic interactions, showing a molecular mass of ∼30 kDa, demonstrating high molecular homogeneity that exists in this family of proteins, is a soft ionization method, in which the samples were ionized by the addition or removal of a proton, with very little extra energy to cause fragmentation of the produced ions. Samples with molecular masses greater than 1200 Da originate multicharged ions (M + nH)n+ in the positive ionization mode; this methodology guarantees that the purified material has a high degree of purity.

RGD-independent binding of Russell's Viper venom Kunitz-type protease inhibitors to platelet GPIIb/IIIa receptor

This study elucidates the platelet-modulating properties of two snake venom Kunitz-type serine protease inhibitors, Rusvikunin and Rusvikunin-II, from Russell’s Viper venom, their native and reconstituted complexes, and two synthetic custom peptides (developed from the platelet-binding region of Rusvikunin-II) against mammalian platelet-rich plasma (PRP) and washed platelets. The Rusvikunins and their complexes demonstrated concentration-dependent deaggregation and aggregation of washed platelets independent of von Willebrand factor and/or fibrinogen requirement. At lower concentrations they abolished collagen and ADP-induced platelet aggregation, but at higher concentrations, they progressively decreased the inhibition of ADP-induced aggregation and potentiated the effect of collagen on PRP. Rusvikunin complex/Rusvikunin-II bound to and induced RGD-independent aggregation of α-chymotrypsin-treated platelets. Molecular docking studies suggested interaction of Rusvikunin-II and custom peptides with platelet GPIIb/IIIa receptor, which was validated by spectrofluorometry analysis and ELISA. This study reports, for the first time, an RGD-independent binding of a snake venom component to the platelet GPIIb/IIIa receptor.

Comparative study of platelet aggregation and secretion induced by Bothrops jararaca snake venom and thrombin

Victims of Bothrops jararaca snakebites manifest bleedings, blood incoagulability, platelet dysfunction, and thrombocytopenia, and the latter has been directly implicated in the genesis of hemorrhagic diathesis. We addressed herein the direct effects of B. jararaca venom (BjV) on ex vivo platelet aggregation and granule secretion in washed human and mouse platelets. BjV directly aggregated platelets, but the extent of platelet aggregation was lower in human than mouse platelets. On the other hand, BjV (24.4 μg/mL) and thrombin (0.1 U/mL) induced a similar extent of ATP and platelet factor 4 (PF4) secretion in both species. BjV-induced platelet aggregation was independent of the platelet dense body content, as in pearl mouse (Ap3b1^-/-) platelets, whose dense bodies are deficient in adenine nucleotides and serotonin, the extent of platelet aggregation was superior to that induced in BALB/c or C57BL/6 mice. BjV-induced β-hexosaminidase secretion in human platelets was less intense than that evoked by thrombin, and the contrary was observed in mouse platelets. Irreversible inactivation of platelet cyclooxygenase 1 by acetylsalicylic acid did not reduce BjV-induced platelet aggregation. BjV exerted no cytotoxic activity in human and mouse platelets, as evaluated by lactate dehydrogenase loss. Eptifibatide, which inhibits the binding of fibrinogen to platelet glycoprotein complex GPIIb-IIIa, differently blocked BjV-induced platelet aggregation in mice and humans. BjV-induced platelet aggregation did not depend on snake venom serine proteinases nor metalloproteinases in mice, whilst serine proteinases were rather important for platelet aggregation in humans. Our results show that BjV induces direct activation, aggregation, and secretion in human and mouse platelets, but it exerts diverse responses in them, which should be considered in comparative studies to understand pathophysiological events during Bothrops envenomation.

Snake venom components in medicine: From the symbolic rod of Asclepius to tangible medical research and application

Both mythologically and logically, snakes have always fascinated man. Snakes have attracted both awe and fear not only because of the elegant movement of their limbless bodies, but also because of the potency of their deadly venoms. Practically, in 2017, the world health organization (WHO) listed snake envenomation as a high priority neglected disease, as snakes inflict up to 2.7 million poisonous bites, around 100.000 casualties, and about three times as many invalidities on man. The venoms of poisonous snakes are a cocktail of potent compounds which specifically and avidly target numerous essential molecules with high efficacy. The individual effects of all venom toxins integrate into lethal dysfunctions of almost any organ system. It is this efficacy and specificity of each venom component, which after analysis of its structure and activity may serve as a potential lead structure for chemical imitation. Such toxin mimetics may help in influencing a specific body function pharmaceutically for the sake of man's health. In this review article, we will give some examples of snake venom components which have spurred the development of novel pharmaceutical compounds. Moreover, we will provide examples where such snake toxin-derived mimetics are in clinical use, trials, or consideration for further pharmaceutical exploitation, especially in the fields of hemostasis, thrombosis, coagulation, and metastasis. Thus, it becomes clear why a snake captured its symbolic place at the Asclepius rod with good reason still nowadays.

BjSP, a novel serine protease from Bothrops jararaca snake venom that degrades fibrinogen without forming fibrin clots

Snake venom serine proteases (SVSPs) are commonly described as capable of affecting hemostasis by interacting with several coagulation system components. In this study, we describe the isolation and characterization of BjSP from Bothrops jararaca snake venom, a serine protease with distinctive properties. This enzyme was isolated by three consecutive chromatographic steps and showed acidic character (pI 4.4), molecular mass of 28 kDa and N-carbohydrate content around 10%. Its partial amino acid sequence presented 100% identity to a serine protease cDNA clone previously identified from B. jararaca venom gland, but not yet isolated or characterized. BjSP was significantly inhibited by specific serine protease inhibitors and showed high stability at different pH values and temperatures. The enzyme displayed no effects on washed platelets, but was able to degrade fibrin clots in vitro and also the Aα and Bβ chains of fibrinogen differently from thrombin, forming additional fibrinopeptides derived from the Bβ chain, which should be related to its inability to coagulate fibrinogen solutions or platelet-poor plasma. In the mapping of catalytic subsites, the protease showed high hydrolytic specificity for tyrosine, especially in subsite S1. Additionally, its amidolytic activity on different chromogenic substrates suggests possible effects on other factors of the coagulation cascade. In conclusion, BjSP is a serine protease that acts nonspecifically on fibrinogen, generating different Bβ fibrinopeptides and thus not forming fibrin clots. Its distinguished properties in comparison to most SVSPs stimulate further studies in an attempt to validate its potential as a defibrinogenating agent.

Molecular modeling, biochemical characterization, and pharmacological properties of Cc3 -SPase: A platelet-aggregating thrombin-like enzyme purified from Cerastes cerastes venom

Cc3 -SPase (30 kDa-proteinase; pI 5.98) was isolated from Cerastes cerastes venom. Its sequence of 271 residues yielded from LC-MALDI-TOF showed high degrees of homology when aligned with other proteinases. Cc3 -SPase cleaved natural and synthetic proteins such as casein and fibrinogen leaving fibrin clots unaffected. Cc3 -SPase was fully abolished by ion chelators, whereas aprotinin, antithrombin III (Sigma Aldrich, Saint-Louis, Missouri, USA), and heparin were ineffective. Affinity of Cc3 -SPase to benzamidine indicated the presence of an aspartate residue in the catalytic site as confirmed by three-dimensional structure consisting of 14 β-strands and four α-helices. Molecular mechanisms revealed that Cc3 -SPase is capable of promoting dysfunctional platelet aggregation via two signaling pathways mediated by the G-coupled protein receptors and αIIbβ3 integrin. Cc3 -SPase is involved in both extrinsic/intrinsic coagulation pathways in deficient plasmas by replacing defective/lacking factors FII, FVII, and FVIII but not FX. Cc3 -SPase could substitute missing factors in blood diseases related to plasma factor deficiencies.

The role of platelets in hemostasis and the effects of snake venom toxins on platelet function

The human body has a set of physiological processes, known as hemostasis, which keeps the blood fluid and free of clots in normal vessels; in the case of vascular injury, this process induces the local formation of a hemostatic plug, preventing hemorrhage. The hemostatic system in humans presents complex physiological interactions that involve platelets, plasma proteins, endothelial and subendothelial structures. Disequilibrium in the regulatory mechanisms that control the growth and the size of the thrombus is one of the factors that favors the development of diseases related to vascular disorders such as myocardial infarction and stroke, which are among the leading causes of death in the western world. Interfering with platelet function is a strategy for the treatment of thrombotic diseases. Antiplatelet drugs are used mainly in cases related to arterial thrombosis and interfere in the formation of the platelet plug by different mechanisms. Aspirin (acetylsalicylic acid) is the oldest and most widely used antithrombotic drug. Although highly effective in most cases, aspirin has limitations compared to other drugs used in the treatment of homeostatic disorders. For this reason, research related to molecules that interfere with platelet aggregation are of great relevance. In this regard, snake venoms are known to contain a number of molecules that interfere with hemostasis, including platelet function. The mechanisms by which snake venom components inhibit or activate platelet aggregation are varied and can be used as tools for the diagnosis and the treatment of several hemostatic disorders. The aim of this review is to present the role of platelets in hemostasis and the mechanisms by which snake venom toxins interfere with platelet function.

Expression of a new serine protease from Crotalus durissus collilineatus venom in Pichia pastoris and functional comparison with the native enzyme

Snake venom serine proteases (SVSPs) act primarily on plasma proteins related to blood clotting and are considered promising for the treatment of several hemostatic disorders. We report the heterologous expression of a serine protease from Crotalus durissus collilineatus, named collinein-1, in Pichia pastoris, as well as the enzymatic comparative characterization of the toxin in native and recombinant forms. The complementary DNA (cDNA) encoding collinein-1 was amplified from cDNA library of C. d. collilineatus venom gland and cloned into the pPICZαA vector. The recombinant plasmid was used to transform cells of KM71H P. pastoris. Heterologous expression was induced by methanol and yielded 56 mg of recombinant collinein-1 (rCollinein-1) per liter of culture. The native collinein-1 was purified from C. d. collilineatus venom, and its identity was confirmed by amino acid sequencing. The native and recombinant enzymes showed similar effects upon bovine fibrinogen by releasing preferentially fibrinopeptide A. Although both enzymes have induced plasma coagulation, native Colinein-1 has shown higher coagulant activity. The serine proteases were able to hydrolyze the chromogenic substrates S-2222, S-2238, and S2302. Both enzymes showed high stability on different pH and temperature, and their esterase activities were inhibited in the presence of Zn2+ and Cu2+. The serine proteases showed similar k cat/K m values in enzyme kinetics assays, suggesting no significant differences in efficiency of these proteins to hydrolyze the substrate. These results demonstrated that rCollinein-1 was expressed with functional integrity on the evaluated parameters. The success in producing a functionally active recombinant SVSP may generate perspectives to their future therapeutic applications.

Combined venomics, venom gland transcriptomics, bioactivities, and antivenomics of two Bothrops jararaca populations from geographic isolated regions within the Brazilian Atlantic rainforest

Bothrops jararaca is a slender and semi-arboreal medically relevant pit viper species endemic to tropical and subtropical forests in southern Brazil, Paraguay, and northern Argentina (Misiones). Within its geographic range, it is often abundant and is an important cause of snakebite. Although no subspecies are currently recognized, geographic analyses have revealed the existence of two well-supported B. jararaca clades that diverged during the Pliocene ~3.8Mya and currently display a southeastern (SE) and a southern (S) Atlantic rainforest (Mata Atlântica) distribution. The spectrum, geographic variability, and ontogenetic changes of the venom proteomes of snakes from these two B. jararaca phylogroups were investigated applying a combined venom gland transcriptomic and venomic analysis. Comparisons of the venom proteomes and transcriptomes of B. jararaca from the SE and S geographic regions revealed notable interpopulational variability that may be due to the different levels of population-specific transcriptional regulation, including, in the case of the southern population, a marked ontogenetic venom compositional change involving the upregulation of the myotoxic PLA2 homolog, bothropstoxin-I. This population-specific marker can be used to estimate the proportion of venom from the southern population present in the B. jararaca venom pool used for the Brazilian soro antibotrópico (SAB) antivenom production. On the other hand, the southeastern population-specific D49-PLA2 molecules, BinTX-I and BinTX-II, lend support to the notion that the mainland ancestor of Bothrops insularis was originated within the same population that gave rise to the current SE B. jararaca phylogroup, and that this insular species endemic to Queimada Grande Island (Brazil) expresses a pedomorphic venom phenotype. Mirroring their compositional divergence, the two geographic B. jararaca venom pools showed distinct bioactivity profiles. However, the SAB antivenom manufactured in Vital Brazil Institute neutralized the lethal effect of both venoms to a similar extent. In addition, immobilized SAB antivenom immunocaptured most of the venom components of the venoms of both B. jararaca populations, but did not show immunoreactivity against vasoactive peptides. The Costa Rican bothropic-crotalic-lachesic (BCL) antivenom showed the same lack of reactivity against vasoactive peptides but, in addition, was less efficient immunocapturing PI- and PIII-SVMPs from the SE venom, and bothropstoxin-I, a CRISP molecule, and a D49-PLA2 from the venom of the southern B. jararaca phylogroup. The remarkable paraspecificity exhibited by the Brazilian and the Costa Rican antivenoms indicates large immunoreactive epitope conservation across the natural history of Bothrops, a genus that has its roots in the middle Miocene. This article is part of a Special Issue entitled: Omics Evolutionary Ecolog.

Crystal structure of Jararacussin-I: the highly negatively charged catalytic interface contributes to macromolecular selectivity in snake venom thrombin-like enzymes

Snake venom serine proteinases (SVSPs) are hemostatically active toxins that perturb the maintenance and regulation of both the blood coagulation cascade and fibrinolytic feedback system at specific points, and hence, are widely used as tools in pharmacological and clinical diagnosis. The crystal structure of a thrombin-like enzyme (TLE) from Bothrops jararacussu venom (Jararacussin-I) was determined at 2.48 Å resolution. This is the first crystal structure of a TLE and allows structural comparisons with both the Agkistrodon contortrix contortrix Protein C Activator and the Trimeresurus stejnegeri plasminogen activator. Despite the highly conserved overall fold, significant differences in the amino acid compositions and three-dimensional conformations of the loops surrounding the active site significantly alter the molecular topography and charge distribution profile of the catalytic interface. In contrast to other SVSPs, the catalytic interface of Jararacussin-I is highly negatively charged, which contributes to its unique macromolecular selectivity.

Rapid purification and procoagulant and platelet aggregating activities of Rhombeobin: a thrombin-like/gyroxin-like enzyme from Lachesis muta rhombeata snake venom

We report a rapid purification method using one-step chromatography of SVSP Rhombeobin (LMR-47) from Lachesis muta rhombeata venom and its procoagulant activities and effects on platelet aggregation. The venom was fractionated by a single chromatographic step in RP-HPLC on a C8 Discovery BIO Wide Pore, showing high degree of molecular homogeneity with molecular mass of 47035.49 Da. Rhombeobin showed amidolytic activity upon BA ρ NA, with a broad optimum pH (7-10) and was stable in solution up to 60°C. The amidolytic activity was inhibited by serine proteinase inhibitors and reducing agents, but not chelating agents. Rhombeobin showed high coagulant activity on mice plasma and bovine fibrinogen. The deduced amino acid sequence of Rhombeobin showed homology with other SVSPs, especially with LM-TL (L. m. muta) and Gyroxin (C. d. terrificus). Rhombeobin acts, in vitro, as a strong procoagulant enzyme on mice citrated plasma, shortening the APTT and PT tests in adose-dependent manner. The protein showed, "ex vivo", a strong defibrinogenating effect with 1 µg/animal. Lower doses activated the intrinsic and extrinsic coagulation pathways and impaired the platelet aggregation induced by ADP. Thus, this is the first report of a venom component that produces a venom-induced consumptive coagulopathy (VICC).

Biochemical characterization and comparative analysis of two distinct serine proteases from Bothrops pirajai snake venom

This study reports the isolation and biochemical characterization of two different serine proteases from Bothrops pirajai snake venom, thus providing a comparative analysis of the enzymes. The isolation process consisted of three consecutive chromatographic steps (Sephacryl S-200, Benzamidine Sepharose and C2/C18), resulting in two serine proteases, named BpirSP27 and BpirSP41 after their molecular masses by mass spectrometry (27,121 and 40,639 Da, respectively). Estimation by SDS-PAGE under denaturing conditions showed that, when deglycosylated with PNGase F, BpirSP27 and BpirSP41 had their molecular masses reduced by approximately 15 and 42%, respectively. Both are acidic enzymes, with pI of approximately 4.7 for BpirSP27 and 3.7 for BpirSP41, and their N-terminal amino acid sequences showed 57% identity to each other, with high similarity to the sequences of other snake venom serine proteases (SVSPs). The enzymes showed different actions on bovine fibrinogen, with BpirSP27 acting preferentially on the Bβ chain and BpirSP41 on both Aα and Bβ chains. The two serine proteases were also able to degrade fibrin and blood clots in vitro depending on the doses and incubation periods, with higher results for BpirSP41. Both enzymes coagulated the human plasma in a dose-dependent manner, and BpirSP41 showed a higher coagulant potential, with minimum coagulant dose (MCD) of ∼3.5 μg versus 20 μg for BpirSP27. The enzymes were capable of hydrolyzing different chromogenic substrates, including S-2238 for thrombin-like enzymes, but only BpirSP27 acted on the substrate S-2251 for plasmin. They also showed high stability against variations of temperature and pH, but their activities were significantly reduced after preincubation with Cu(2+) ion and specific serine protease inhibitors. In addition, BpirSP27 induced aggregation of washed platelets to a greater extent than BpirSP41. The results showed significant structural and functional differences between B. pirajai serine proteases, providing interesting insights into the structure-function relationship of SVSPs.

Isolation and characterisation of a kallikrein-like enzyme from Agkistrodon halys pallas snake venom

BACKGROUND

Viper snake venoms contain a great variety of toxic proteins. These components mediate their toxicity by either stimulating or inhibiting the haemostatic system of human victims or experimental animals, resulting in common clinical complications of blood clotting or uncontrolled haemorrhage. Therefore it is deemed important to isolate the active component(s) from snake venom with kallikrein-like activity.

RESULTS

A kallikrein-like proteinase of Agkistrodon halys pallas snake venom, designated AHP-Ka, was purified by anion exchange chromatography and affinity chromatography. Physicochemical studies showed that the purified enzyme was a 34 kDa monomeric glycoprotein, the molecular weight of which decreased to 26 kDa after deglycosylation with peptide N-glycosidase F (PNGase F). Sequence studies on the NH(2) -terminal region of the protein indicated that AHP-Ka shared a high degree of sequence homology with other serine proteinases from snake venoms. AHP-Ka showed high catalytic activity and kallikrein-like activity on substrates such as arginine esterase BAEE and chromogenic H-D-Pro-Phe-Arg-pNA·2HCl (S-2302) and was inhibited by protease inhibitor phenylmethylsulfonyl fluoride (PMSF).

CONCLUSION

The results showed that AHP-Ka isolated from A. halys pallas snake venom and purified by anion exchange chromatography and affinity chromatography is in fact a kallikrein-like enzyme.

Hemostatic and toxinological diversities in venom of Micrurus tener tener, Micrurus fulvius fulvius and Micrurus isozonus coral snakes

The coral snake Micrurus tener tener (Mtt) from the Elapidae family inhabits the southwestern United States and produces severe cases of envenomations. Although the majority of Mtt venom components are neurotoxins and phospholipase A₂s, this study demonstrated, by SDS-PAGE and molecular exclusion chromatography (MEC), that these venoms also contain high-molecular-weight proteins between 50 and 150 kDa that target the hemostatic system. The biological aspects of other Micrurus venoms were also studied, such as the LD₅₀s of Micrurus isozonus (from 0.52 to 0.61 mg/kg). A pool from these venoms presented a LD₅₀ of 0.57 mg/kg, Micrurus f. fulvius (Mff) and Mtt had LD₅₀s of 0.32 and 0.78 mg/kg, respectively. These venoms contained fibrino(geno)lytic activity, they inhibited platelet aggregation, as well as factor Xa and/or plasmin-like activities. M. isozonus venoms from different Venezuelan geographical regions inhibited ADP-induced platelet aggregation (from 50 to 68%). Micrurus tener tener venom from the United States was the most active with a 95.2% inhibitory effect. This venom showed thrombin-like activity on fibrinogen and human plasma. Fractions of Mtt showed fibrino(geno)lytic activity and inhibition on plasmin amidolytic activity. Several fractions degraded the fibrinogen Aα chains, and fractions F2 and F7 completely degraded both fibrinogen Aα and Bβ chains. To our knowledge, this is the first report on thrombin-like and fibrino(geno)lytic activity and plasmin or factor Xa inhibitors described in Micrurus venoms. Further purification and characterization of these Micrurus venom components could be of therapeutic use in the treatment of hemostatic disorders.

Haemostatically active proteins in snake venoms

Snake venom proteins that affect the haemostatic system can cause (a) lowering of blood coagulability, (b) damage to blood vessels, resulting in bleeding, (c) secondary effects of bleeding, e.g. hypovolaemic shock and organ damage, and (d) thrombosis. These proteins may, or may not, be enzymes. We review the data on the most relevant haemostatically active proteinases, phospholipases A₂, L-amino acid oxidases and 5'-nucleotidases from snake venoms. We also survey the non-enzymatic effectors of haemostasis from snake venoms--disintegrins, C-type lectins and three-finger toxins. Medical applications have already been found for some of these snake venom proteins. We describe those that have already been approved as drugs to treat haemostatic disorders or are being used to diagnose such health problems. No clinical applications, however, currently exist for the majority of snake venom proteins acting on haemostasis. We conclude with the most promising potential uses in this respect.

Soluble expression, purification, and characterization of Gloydius shedaoensis venom gloshedobin in Escherichia coli by using fusion partners

Gloshedobin, a thrombin-like enzyme from the venom of Gloydius shedaoensis, is usually produced as inclusion bodies in Escherichia coli cell. In this work, gloshedobin was separately fused with three fusion partners NusA, GST, and TrxA at its N terminus and then was expressed as fusion proteins in E. coli. The results showed that the NusA was the most efficient fusion partner to improve the solubility of recombinant gloshedobin. The purified NusA-fused gloshedobin with an overall yield of 64.6% was resolved as one band in the SDS-PAGE gel with molecular mass of about 90 kDa. Both fibrinogen clotting and fibrinogenolytic activities were found for the recombinant product. The purified NusA-fused gloshedobin exhibited amidolytic activity of 506 U/mg under optimal conditions of pH of 8.0 and 40 degrees C. The inhibition study of NusA-fused gloshedobin by various inhibitors showed that serine protease inhibitors, phenylmethylsulphonyl fluoride, and N-tosyl-L: -phenylalanine chloromethyl ketone, strongly inhibited its admidolytic activity, whereas ethylenediaminetetraacetic acid as well as heparin and hirudin did not, suggesting that NusA-fused gloshedobin exhibited the same characteristics as the native form of gloshedobin. The strategy of this work may contribute to improve the soluble expression level of other thrombin-like enzymes from snake venom in E. coli.

Biochemical and functional properties of a thrombin-like enzyme isolated from Bothrops pauloensis snake venom

In the present study, a thrombin-like enzyme named BpSP-I was isolated from Bothrops pauloensis snake venom and its biochemical, enzymatic and pharmacological characteristics were determined. BpSP-I is a glycoprotein that contains both N-linked carbohydrates and sialic acid in its structure, with M(r)=34,000 under reducing conditions and pI approximately 6.4. The N-terminal sequence of the enzyme (VIGGDECDINEHPFL) showed high similarity with other thrombin-like enzymes from snake venoms. BpSP-I showed high clotting activity upon bovine and human plasma and was inhibited by PMSF, benzamidine and leupeptin. Moreover, this enzyme showed stability when examined at different temperatures (-70 to 37 degrees C), pH values (3-9) or in the presence of divalent metal ions (Ca(2+), Mg(2+), Zn(2+) and Mn(2+)). BpSP-I showed high catalytic activity upon substrates, such as fibrinogen, TAME, S-2238 and S-2288. It also showed kallikrein-like activity, but was unable to act upon factor Xa and plasmin substrates. Indeed, the enzyme did not induce hemorrhage, myotoxicity or edema. Taken together, our data showed that BpSP-I is in fact a thrombin-like enzyme isoform isolated from Bothrops pauloensis snake venom.

Bothrops protease A, a unique highly glycosylated serine proteinase, is a potent, specific fibrinogenolytic agent

BACKGROUND

The hemostatic system is the major target of snake venom serine proteinases (SVSPs) that act on substrates of the coagulation, fibrinolytic and kallikrein-kinin systems. Bothrops protease A (BPA), the most glycosylated SVSP, is a non-coagulant, thermostable enzyme. A cDNA encoding BPA showed that the protein has a calculated molecular mass of 25 409 Da, implying that approximately 62% of its molecular mass as assessed by sodium dodecylsulfate polyacrylamide gel electrophoresis (67 kDa) is due to carbohydrate moieties.

RESULTS

Here we show that BPA is a potent fibrinogenolytic agent in vitro, as it readily degraded human and rat fibrinogen at a very low enzyme concentration. Partially N-deglycosylated BPA (p-N-d-BPA) generated similar fibrinogen products, but with enhanced fibrinogenolytic activity. In vivo, injection of 0.75 nmoles of BPA in rats completely avoided thrombus formation induced by stasis in the vena cava, or by endothelium injury in the jugular vein. Moreover, it decreased the fibrinogen plasma level and prolonged the recalcification time. Cleavage of fibrinogen in human and rat plasma was observed with native BPA and p-N-d-BPA by electrophoresis followed by western blot using an anti-fibrinogen antibody. BPA did not cause unspecific degradation of plasma proteins and did not cleave isolated albumin, vitronectin and fibronectin at the same concentration used with fibrinogen. Serine proteinase inhibitors failed to inhibit BPA, probably due to steric hindrance caused by its huge carbohydrate moieties.

CONCLUSIONS

To the best of our knowledge, this investigation underscores a new, thermostable, specific defibrinogenating agent that may have an application in the prevention of thrombus formation.

Hemorrhagic, coagulant and fibrino(geno)lytic activities of crude venom and fractions from mapanare (Bothrops colombiensis) snakes

Bothrops colombiensis venom from two similar geographical locations were tested for their hemostatic functions and characterized by gel-filtration chromatography and SDS-PAGE electrophoresis. The snakes were from Caucagua and El Guapo towns of the Venezuelan state of Miranda. Fibrino(geno)lytic, procoagulant, hemorrhagic, lethal activities, gel-filtration chromatography and SDS-PAGE profiles were analyzed and compared for both venoms. The highest hemorrhagic activity of 5.3 mug was seen in El Guapo venom while Caucagua venom had the lowest LD(50) of 5.8 mg/kg. Both venoms presented similar thrombin-like activity. El Guapo showed a factor Xa-like activity two times higher than Caucagua. Differences were observed in kallikrein-like and t-PA activities, being highest in El Guapo. Caucagua venom showed the maximum fibrin lysis. Both crude venom runs on Sephadex G-100 chromatography gave fraction SII with the high fibrinolytic activity. Proteases presented in SII fractions and eluted from Benzamidine-Sepharose (not bound to the column) provoked a fast degradation of fibrinogen alpha chains and a slower degradation of beta chains, which could possibly be due to a higher content of alpha fibrinogenases in these venoms. The fibrinogenolytic activity was decreased by metalloprotease inhibitors. The results suggested that metalloproteases in SII fractions were responsible for the fibrinolytic activity. The analysis of samples for fibrin-zymography of SII fractions showed an active band with a molecular mass of approximately 30 kDa. These results reiterate the importance of using pools of venoms for antivenom immunization, to facilitate the neutralization of the maximum potential number of toxins.

The venom gland transcriptome of the Desert Massasauga rattlesnake (Sistrurus catenatus edwardsii): towards an understanding of venom composition among advanced snakes (Superfamily Colubroidea)

Background

Snake venoms are complex mixtures of pharmacologically active proteins and peptides which belong to a small number of superfamilies. Global cataloguing of the venom transcriptome facilitates the identification of new families of toxins as well as helps in understanding the evolution of venom proteomes.

Results

We have constructed a cDNA library of the venom gland of a threatened rattlesnake (a pitviper), Sistrurus catenatus edwardsii (Desert Massasauga), and sequenced 576 ESTs. Our results demonstrate a high abundance of serine proteinase and metalloproteinase transcripts, indicating that the disruption of hemostasis is a principle mechanism of action of the venom. In addition to the transcripts encoding common venom proteins, we detected two varieties of low abundance unique transcripts in the library; these encode for three-finger toxins and a novel toxin possibly generated from the fusion of two genes. We also observed polyadenylated ribosomal RNAs in the venom gland library, an interesting preliminary obsevation of this unusual phenomenon in a reptilian system.

Conclusion

The three-finger toxins are characteristic of most elapid venoms but are rare in viperid venoms. We detected several ESTs encoding this group of toxins in this study. We also observed the presence of a transcript encoding a fused protein of two well-characterized toxins (Kunitz/BPTI and Waprins), and this is the first report of this kind of fusion in a snake toxin transcriptome. We propose that these new venom proteins may have ancillary functions for envenomation. The presence of a fused toxin indicates that in addition to gene duplication and accelerated evolution, exon shuffling or transcriptional splicing may also contribute to generating the diversity of toxins and toxin isoforms observed among snake venoms. The detection of low abundance toxins, as observed in this and other studies, indicates a greater compositional similarity of venoms (though potency will differ) among advanced snakes than has been previously recognized.

BJ-48, a novel thrombin-like enzyme from the Bothrops jararacussu venom with high selectivity for Arg over Lys in P1: Role of N-glycosylation in thermostability and active site accessibility

BJ-48, a serine protease from the venom of Bothrops jararacussu, was purified to homogeneity using affinity chromatography on p-aminobenzamidine-agarose followed by HPLC gel filtration. BJ-48 presented 52kDa by SDS-PAGE analysis and 48,036Da by electron spray mass spectrometry. The enzyme was shown to be highly glycosylated with 42% of N-linked carbohydrates composed of Fuc(1):GalN(4):GlcN(5):Gal(1):Man(2) and a high content of sialic acid residues (8-12%). BJ-48 had optimal esterase activity at pH 7.5 and displayed maximum catalytic rate at 50 degrees C. Its hydrolytic activity was strongly inhibited by aprotinin and dithiothreitol while N-tosyl-l-phenylalanine chloromethyl ketone, 6-aminocaproic acid, E-64 and soybean trypsin inhibitor (SBTI) were ineffective. The kinetics of BJ-48 with chromogenic substrates revealed an unprecedented selectivity (10(4)-fold) for Arg over Lys in P1. BJ-48 proved to be a thrombin-like enzyme (TLE) with a specific fibrinogen-clotting activity of 73.4NIH units/mg. The TLE rapidly digested human fibrinogen Bbeta chain, but the Aalpha chain was cleaved specifically to release fibrinopeptide A with k(cat)/K(m)=2.1 microM(-1)s(-1). The TLE showed no activity toward other thrombin substrates like protein C, protease-activated receptor-1 or inhibitors such as hirudin and antithrombin. A non-denaturing procedure using PNGase F and neuraminidase followed by hydrophobic interaction chromatography was employed to obtain active BJ-48 forms with variable carbohydrate content. Compared to the native enzyme, total or partially deglycosylated BJ-48 forms presented up to 2-fold reduction in their specific activities upon heating at 55/65 degrees C or treatment with SBTI. These results point out a role for BJ-48 glycosylation in thermostability and controlling the access of some canonical protein inhibitors to the active site.

Sexual dimorphism in venom of Bothrops jararaca(Serpentes: Viperidae)

Bothrops jararaca is an abundant snake in Brazil, and its venom has been studied exhaustively. The species exhibits adult size dimorphism in which female are larger. We registered the growth in Snout-Vent Length and weight of one litter (with 11 females and 12 males). We compared growth curves and venom profile between male and female of B. jararaca in order to establish the relationship of those characters and sex. Their venoms were analyzed when they were 36 months old, concerning SDS PAGE, protein content, proteolytic, hyaluronidasic, phospholipasic, blood-clotting, edematogenic, hemorrhagic, myotoxic activities, and lethality. Differences in the growth curves of the females and the males were significantly different after the 12th month of age, with the females growing faster. Females produced five times more venom than males. The electrophoretic patterns were variable: the venom from males had more protein bands than females. Venom composition varied significantly between males and females. Venom from females is more potent for hyaluronidasic, hemorrhagic, and lethality activities, whereas venom from males is more potent for coagulant, phospholipasic, and myotoxic activities. The variability of proteolytic and edematogenic activities were not significant. The important sexual dimorphism in body size and mass, amount of venom produced, and venom composition in B. jararaca may reflect a divergence in niche partitioning.

Sex-based individual variation of snake venom proteome among eighteen Bothrops jararaca siblings

Variation of venom proteome is relevant to basic research, to management of envenoming, and to studies on the evolution of poisonous snakes. In this study, we explored the venom proteomes of eighteen Bothrops jararaca specimens of a single litter born and raised in laboratory. Using electrophoretic techniques and various protocols for measuring the proteolytic activities of these venoms we have detected individual variability and highlighted sex-specific proteomic similarities and differences among sibling snakes. SDS-polyacrylamide gel electrophoresis under non-reducing conditions showed protein bands of approximately 100 kDa specific of male venoms. 2D-electrophoresis showed regions with varying spot complexity between pooled female and male venoms as well as spots that were gender specific. Gelatin zymography showed that female venoms contained proteinases of approximately 25 kDa absent from male venoms. Female venoms were more active than male venoms in degrading fibrinogen whereas on fibrin no significant differences were detected. Among various chromogenic peptide substrates tested, male venoms showed higher amidolytic activity than female venoms on D-Val-Leu-Lys-pNA and D-Phe-Pip-Arg-pNA. Taken together, these results show sex-based differences in the venom proteome of sibling snakes of a single litter raised under controlled conditions which seem to be genetically inherited and imposed by evolutionary forces.

Purification and properties of a coagulant thrombin-like enzyme from the venom of Bothrops leucurus

A thrombin-like enzyme from Bothrops leucurus venom, named leucurobin (leuc), was purified by gel filtration, affinity and ion exchange chromatographies. Physicochemical studies indicated that the purified enzyme is a 35 kDa monomeric glycoprotein on SDS-PAGE under reducing conditions, which decreased to 29 kDa after deglycosylation with N-glycosidase F (PNGase F). The amino acid sequence of leuc was determined by automated sequencing of the intact native protein and peptides produced by digestion of the S-pyridyl-ethylated protein with trypsin. The protein sequence exhibits significant similarities with other serine proteases reported from snake venoms, and contains two potential sites of N-linked glycosylation. The proteinase split off fibrinopeptide A (FPA) rapidly from human fibrinogen; however, only negligible traces of fibrinopeptide B (FPB) were observed. In addition, the enzyme released the N-terminal peptide (Mr=4572) containing the first 42 residues from the Bbeta-chain. Leuc could neither activate factor XIII nor release kinins from heat-treated bovine plasma. Its specific clotting activity was equivalent to 198 NIH thrombin U/mg on human fibrinogen. Kinetic properties of leuc were determined using representative chromogenic substrates. The enzyme evoked the gyroxin syndrome when injected into the tail veins of mice at levels of 0.143 microg/g mouse. The inhibitory effects of PMSF and benzamidine on the amidolytic activity suggest that leuc is a serine proteinase, and inhibition by beta-mercaptoethanol revealed the important role of the disulfide bonds in the stabilization of the native structure. Antibothropic serum, SBTI and EDTA had little or no effect on its amidolytic activity. However, the clotting effect of the enzyme was strongly inhibited by antibothropic serum. A Dixon plot showed that the hydrolysis of Bz-L-Arg-pNA by leuc was competitively inhibited by benzamidine (Ki=1.61+/-0.25 mM).

Shedaoenase, a novel fibrinogenase from the venom of Agkistrodon shedaoenthesis Zhao

Shedaoenase, a serine protease, was isolated from the venom of Agkistrodon shedaoenthesis Zhao with an apparent molecular mass of 36 kDa. It was purified by affinity chromatography on arginine Sepharose 4B column and anion exchange on Mono Q fast protein liquid chromatography. Shedaoenase preferentially cleaved the Aalpha-chain of human fibrinogen and slowly digested the Bbeta-chain. It also showed arginyl esterase activity using Nalpha-benzoyl-L-arginine ethyl ester as a substrate, and some synthetic chromogentic substrates, such as Chromozym PL, S-2266, and S-2160, could also be hydrolyzed. The enzyme activity of shedaoenase could be completely inhibited by phenylmethylsulphonylfluoride and could be little inhibited by the chelating reagent EDTA. The N-terminal sequence of shedaoenase was determined, and its full-length cDNA encoding a protein of 238 amino acid residues was cloned by reverse transcription-polymerase chain reaction from the total mRNA extracted from the snake venom gland. The deduced primary sequence of shedaoenase shares significant homology with other snake venom serine proteases.

Purification, primary structures and evolution of coagulant proteases from Deinagkistrodon actus venom

Deinagkistrodon (formerly Agkistrodon) actus (Taiwan) snake venom was found to contain at least seven closely related coagulant proteases. One of them, named actibin, was purified to homogeneity by means of four chromatographic steps. Actibin acted on fibrinogen to form fibrin clots with extremely high specific activity of 1,630 NIH units/mg and preferentially released fibrinopeptide A. Actibin was an acidic glycoprotein (pI 3.4) with molecular weight of 41,000, which was reduced to 28,800 after deglycosylation with N-glycanase. The k(cat)/K(m) values of actibin for hydrolysis of tosyl-l-arginine methyl ester and benzoyl-l-arginine p-nitroanilide were one-third to a half those for thrombin, reflecting a high potency of actibin in fibrinogen clotting. The amidase activities of actibin and its family proteases were inhibited by 3,4-dichloroisocoumarin, a serine protease inhibitor, indicating that actibin and its family proteases are serine proteases. Four cDNAs, named DaP1 and DaP7-DaP9, encoding D. actus coagulant proteases were cloned. All cDNAs contain an open reading frame of 780 bp coding for 260 amino acid residues, including a signal peptide of 24 amino acid residues. Their amino acid sequences predicted are highly homologous to one another with one to five amino acid substitutions. When four D. actus protease cDNAs were compared with the cDNAs coding for Trimeresurus flavoviridis and T. gramineus venom serine proteases, accelerated evolution was clearly observed. Similarity of the nucleotide sequences of four D. actus protease cDNAs with no synonymous and one to five nonsynonymous substitutions seems not to be in direct conformity with accelerated evolution. This possibly suggests that they have evolved to a similar direction to enhance their clotting activity rather than to produce other physiological activities.