Defibrinogenating enzymes

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.

Hematology products from snake venoms

Venoms have primarily been used to prepare antivenoms for the treatment of snake bites, but they have constituents that might serve other medical needs. These include metalloproteinases, serine proteases, phospholipases, and C-type lectin-like proteins. Some of the products that have been prepared from venoms are procoagulants employed as topical hemostatics, and either applied directly to bleeding wounds or used as adjuncts to surgical procedures to assist in controlling blood loss. Venoms are also a valuable source of laboratory reagents helpful in diagnosing specific coagulation factor deficiencies, identifying lupus anticoagulants, or managing therapeutic anticoagulation. In addition, the unique properties of certain venom components have led to their use as antithrombotic agents. This review describes how snake venoms have provided insight into coagulation mechanisms and generated products to improve human health. Venomous snakes are dangerous but we must learn to safely share our planet with them, not least because studies of their venoms might lead to the discovery of valuable biomolecules.

Effects of batroxobin on the antithrombotic system in patients with cerebral venous thrombosis: Clues to mechanisms

BACKGROUND AND PURPOSE

More evidence supports the benefits of batroxobin combined with anticoagulation in correcting acute cerebral venous thrombosis (CVT). The dynamic fluctuations of peripheral blood platelets, fibrinolysis, and coagulation biomarkers during this therapy were analyzed.

METHODS

We investigated batroxobin's effects on the antithrombotic system under two regimens. The pretreatment group included patients on anticoagulants for at least 1 week before starting batroxobin. The simultaneous treatment group began both treatments upon admission. The control group received only anticoagulation. Batroxobin was given on alternate days at doses of 10BU, 5BU, and 5BU, totaling three doses. Anticoagulation was continuous. Baseline data were T0; the next day after each batroxobin dose was T1, T2, and T3. Data from these four time points was analyzed.

RESULTS

The time-point paired sample T-test results of the pretreatment group [n = 60; mean age (SD), 43.3(16.5); 38 (63.35%) women] showed that batroxobin significantly inhibited ADP-induced platelet aggregation rate (T1-T0: p = 0.015; T2-T0: p = 0.025; T3-T0: p = 0.013), decreased fibrinogen level (T1-T0: p < 0.001; T2-T0: p < 0.001; T3-T0: p < 0.001), and increased D-dimer (T1-T0:p < 0.001; T2-T0: p < 0.001; T3-T0: p < 0.001), TT (T1-T0:p = 0.046; T2-T0: p = 0.003; T3-T0: p < 0.001), and APTT (T1-T0:p = 0.021; T2-T0: p = 0.012; T3-T0: p = 0.026). Compared to the control group, the simultaneous treatment group showed significantly higher TT (T2: p = 0.002; T3: p = 0.004) and D-dimer (T1: p < 0.001; T2: p < 0.001; T3: p < 0.001) values, while fibrinogen (T2: p < 0.001; T3: p < 0.001) levels were significantly lower. Using batroxobin can alleviate the amplitude of changes in coagulation indicators other than TT caused by anticoagulants. The above conclusions are consistent with the results of repeated measurement data analysis.

CONCLUSIONS

Batroxobin can significantly inhibit ADP-induced platelet aggregation rate, increase D-dimer, decrease fibrinogen, and prolong TT and APTT in the presence of anticoagulant agents. Using batroxobin can reduce the amplitude of changes in coagulation indicators caused by anticoagulants. These results reveal the potential mechanism of batroxobin combined with anticoagulation in the safe and effective treatment of CVT.

Randomized, placebo-controlled study on efficacy, safety and tolerability of drug-induced defibrinogenation for sudden sensorineural hearing loss: the lessons learned

PURPOSE

Disturbance of cochlear microcirculation is discussed as final common pathway of various inner ear diseases. Hyperfibrinogenemia causing increased plasma viscosity is a possible factor for a critical reduction of cochlear blood flow that might lead to sudden sensorineural hearing loss (SSHL). The aim was to determine the efficacy and safety of drug-induced defibrinogenation by ancrod for SSHL.

METHODS

Double-blind, randomized, placebo-controlled, multicenter, parallel group, phase II (proof-of-concept) study (planned enrollment: 99 patients). Patients received an infusion of ancrod or placebo (day 1) followed by subcutaneous administrations (day 2, 4, 6). Primary outcome was the change in pure tone audiogram air conduction average until day 8.

RESULTS

The study was terminated early due to slow recruiting (31 enrolled patients: 22 ancrod, 9 placebo). A significant improvement of hearing loss was registered in both groups (ancrod: - 14.3 dB ± 20.4 dB, - 39.9% ± 50.4%; placebo: - 22.3 dB ± 13.7 dB, - 59.1% ± 38.0%). A statistically significant group-difference was not detected (p = 0.374). Placebo response of 33.3% complete and 85.7% at least partial recovery was observed. Plasma fibrinogen levels were reduced significantly by ancrod (baseline: 325.2 mg/dL, day 2: 107.2 mg/dL). Ancrod was tolerated well, no adverse drug reaction was of severe intensity, no serious adverse events occurred.

CONCLUSION

Ancrod reduced fibrinogen levels that support its mechanism of action. The safety profile can be rated positively. Since the planned number of patients could not be enrolled, no efficacy conclusion can be drawn. The high rate of placebo response challenges clinical trials for SSHL and needs to be considered in future investigations. Trial registrations This study was registered in the EU Clinical Trials Register, EudraCT-No. 2012-000066-37 at 2012-07-02.

Short-term effects of intravenous batroxobin in treatment of sudden sensorineural hearing loss: a propensity score-matched study

Background

Sudden sensorineural hearing loss (SSNHL) can cause great panic in patients. Whether it is advantageous to add intravenous batroxobin in the treatment of SSNHL remains to be determined. This study aimed to compare the short-term efficacy of therapy combined with intravenous batroxobin and that without intravenous batroxobin in SSNHL patients.

Methods

This retrospective study harvested the data of SSNHL patients hospitalized in our department from January 2008 to April 2021. The hearing levels on the admitted day (before treatment) and the discharge day were considered pre-treatment hearing and post-treatment hearing, respectively. The hearing gain was the difference value of pre-treatment hearing and post-treatment hearing. We used Siegel's criteria and the Chinese Medical Association of Otolaryngology (CMAO) criteria to evaluate hearing recovery. The complete recovery rate, overall effective rate, and hearing gain at each frequency were considered outcomes. Propensity score matching (PSM) was conducted to balance the baseline characteristics between the batroxobin group and the non-batroxobin group. Sensitivity analysis was carried out in flat-type and total-deafness SSNHL patients.

Results

During the study period, 657 patients with SSNHL were admitted to our department. Among them, a total of 274 patients met the enrolled criteria of our study. After PSM, 162 patients (81 in each group) were included in the analysis. Once the hospitalized treatment was completed, the patients would be discharged the next day. Logistic regression analysis of the propensity score-matched cohort indicated that both the complete recovery rates [Siegel's criteria, OR: 0.734, 95% CI: 0.368-1.466, p = 0.381; CMAO criteria, OR: 0.879, 95% CI: 0.435-1.777, p = 0.720] and the overall effective rates [Siegel's criteria and CMAO criteria, OR: 0.741, 95% CI: 0.399-1.378, p = 0.344] were not significantly different between the two treatment groups. Sensitivity analysis has shown similar results. For flat-type and total-deafness SSNHL patients, no significant difference was found in post-treatment hearing gain at each frequency between the two groups after PSM.

Conclusion

There was no significant difference in short-term hearing outcomes between treatment with batroxobin and treatment without batroxobin in SSNHL patients by Siegel's and CMAO criteria after PSM. Future studies for better therapy regimens of SSNHL are still needed.

Analysis of the Composition of Deinagkistrodon acutus Snake Venom Based on Proteomics, and Its Antithrombotic Activity and Toxicity Studies

There is a strong correlation between the composition of Deinagkistrodon acutus venom proteins and their potential pharmacological effects. The proteomic analysis revealed 103 proteins identified through label-free proteomics from 30 different snake venom families. Phospholipase A2 (30.0%), snaclec (21.0%), antithrombin (17.8%), thrombin (8.1%) and metalloproteinases (4.2%) were the most abundant proteins. The main toxicity of Deinagkistrodon acutus venom is hematotoxicity and neurotoxicity, and it acts on the lung. Deinagkistrodon acutus venom may have anticoagulant and antithrombotic effects. In summary, the protein profile and related toxicity and pharmacological activity of Deinagkistrodon acutus venom from southwest China were put forward for the first time. In addition, we revealed the relationship between the main toxicity, pharmacological effects, and the protein components of snake venom.

Suppression of fibrin(ogen)-driven pathologies in disease models through controlled knockdown by lipid nanoparticle delivery of siRNA

Fibrinogen plays a pathologic role in multiple diseases. It contributes to thrombosis and modifies inflammatory and immune responses, supported by studies in mice expressing fibrinogen variants with altered function or with a germline fibrinogen deficiency. However, therapeutic strategies to safely and effectively tailor plasma fibrinogen concentration are lacking. Here, we developed a strategy to tune fibrinogen expression by administering lipid nanoparticle (LNP)-encapsulated small interfering RNA (siRNA) targeting the fibrinogen α chain (siFga). Three distinct LNP-siFga reagents reduced both hepatic Fga messenger RNA and fibrinogen levels in platelets and plasma, with plasma levels decreased to 42%, 16%, and 4% of normal within 1 week of administration. Using the most potent siFga, circulating fibrinogen was controllably decreased to 32%, 14%, and 5% of baseline with 0.5, 1.0, and 2.0 mg/kg doses, respectively. Whole blood from mice treated with siFga formed clots with significantly decreased clot strength ex vivo, but siFga treatment did not compromise hemostasis following saphenous vein puncture or tail transection. In an endotoxemia model, siFga suppressed the acute phase response and decreased plasma fibrinogen, D-dimer, and proinflammatory cytokine levels. In a sterile peritonitis model, siFga restored normal macrophage migration in plasminogen-deficient mice. Finally, treatment of mice with siFga decreased the metastatic potential of tumor cells in a manner comparable to that observed in fibrinogen-deficient mice. The results indicate that siFga causes robust and controllable depletion of fibrinogen and provides the proof-of-concept that this strategy can modulate the pleiotropic effects of fibrinogen in relevant disease models.

Association Between the Number of Intratympanic Steroid Injections and Hearing Recovery in Sudden Sensorineural Hearing Loss

The frequency of intratympanic (IT) steroid injection varies from once daily to once weekly or less among studies and does not reach a uniform standard. This study investigated the potential association between the number of IT steroid injections and hearing recovery to determine the optimal number in sudden sensorineural hearing loss (SSNHL) patients. A retrospective study involving 233 SSNHL patients receiving IT steroids plus batroxobin within 7 days of onset was performed. Patients were followed up for 3 months. More than 15 dB of HL improvement in the pretreatment pure tone average (PTA) was defined as effective. The effective group had a higher IT injection numbers than the ineffective group (≥ 6 times: 84.6 vs. 61.1, p < 0.001). Regardless of the unadjusted model or adjusted model, patients who received more frequent IT steroid injections seemed more likely to recover hearing (unadjusted model, OR, 95% CI: 1.25, 1.06-1.48; p = 0.007; adjusted model, OR, 95% CI: 1.21, 1.01-1.45; p = 0.044). Six IT injections had the highest rate of hearing recovery (79.1%). In conclusion, IT injection number was an independent factor that was positively associated with hearing recovery, and the optimal number of IT steroid injections was 6. Batroxobin plus higher number of IT steroid injections showed more effective for treating SSNHL.

In silico biophysics and hemorheology of blood hyperviscosity syndrome

Hyperviscosity syndrome (HVS) is characterized by an increase of the blood viscosity by up to seven times the normal blood viscosity, resulting in disturbances to the circulation in the vasculature system. HVS is commonly associated with an increase of large plasma proteins and abnormalities in the properties of red blood cells, such as cell interactions, cell stiffness, and increased hematocrit. Here, we perform a systematic study of the effect of each biophysical factor on the viscosity of blood by employing the dissipative particle dynamic method. Our in silico platform enables manipulation of each parameter in isolation, providing a unique scheme to quantify and accurately investigate the role of each factor in increasing the blood viscosity. To study the effect of these four factors independently, each factor was elevated more than its values for a healthy blood while the other factors remained constant, and viscosity measurement was performed for different hematocrits and flow rates. Although all four factors were found to increase the overall blood viscosity, these increases were highly dependent on the hematocrit and the flow rates imposed. The effect of cell aggregation and cell concentration on blood viscosity were predominantly observed at low shear rates, in contrast to the more magnified role of cell rigidity and plasma viscosity at high shear rates. Additionally, cell-related factors increase the whole blood viscosity at high hematocrits compared with the relative role of plasma-related factors at lower hematocrits. Our results, mapped onto the flow rates and hematocrits along the circulatory system, provide a correlation to underpinning mechanisms for HVS findings in different blood vessels.

Priapism following a juvenile Russell's viper bite: An unusual case report

Following a bite from a juvenile Russell's viper (Daboia russelii), a priapism (painful erection) developed rapidly in a 16-year-old male and only subsided after administration of antivenom 3 hours later. Potential mechanisms for this snakebite-induced priapism are unclear but likely due to venom toxins causing nitric oxide (NO) release and subsequent vasodilation of endothelium in the corpus cavernosum, although the possible involvement of other mechanisms cannot be ruled out. We strongly believe that this unusual case report may lead to further scientific research in order to improve the clinical understanding of the pathophysiology of envenomation due to Russell's viper bites. Although it is too early to speculate, further research may also discover the possibilities of developing venom-based candidate molecules to treat sexual dysfunction in males and females.

Batroxobin inhibits astrocyte activation following nigrostriatal pathway injury

Batroxobin is a thrombin-like serine protease from the venom of the Bothrops atrox and Bothrops moojeni snake species. Sirtuin 1 (Sirt1) has been shown to play an important role in neuroprotection after traumatic brain injury. However, its underlying mechanism of action remains poorly understood. The purpose of this study was to investigate whether the mechanism by which batroxobin participates in the activation of astrocytes is associated with Sirt1. Mouse models of nigrostriatal pathway injury were established. Immediately after modeling, mice were intraperitoneally administered 39 U/kg batroxobin. Batroxobin significantly reduced the expression of cleaved caspase-3 in both the substantia nigra and striatum, inhibited neuronal apoptosis, and promoted the recovery of rat locomotor function. These changes coincided with a remarkable reduction in astrocyte activation. Batroxobin also reduced Sirt1 expression and extracellular signal-regulated kinase activation in brain tissue. Intraperitoneal administration of the Sirt1-specific inhibitor EX527 (5 mg/kg) 30 minutes prior to injury could inhibit the abovementioned effects. In mouse astrocyte cultures, 1 ng/mL batroxobin attenuated interleukin-1β-induced activation of astrocytes and extracellular signal-regulated kinase. EX527 could also inhibit the effects of batroxobin. These findings suggest that batroxobin inhibits astrocyte activation after nigrostriatal pathway injury through the Sirt1 pathway. This study was approved by the Animal Ethics Committee of China Medical University, China (approval No. CMU2020037) on July 19, 2015.

Clinical implications of differential antivenom efficacy in neutralising coagulotoxicity produced by venoms from species within the arboreal viperid snake genus Trimeresurus

Snake envenomation globally is attributed to an ever-increasing human population encroaching into snake territories. Responsible for many bites in Asia is the widespread genus Trimeresurus. While bites lead to haemorrhage, only a few species have had their venoms examined in detail. We found that Trimeresurus venom causes haemorrhaging by cleaving fibrinogen in a pseudo-procoagulation manner to produce weak, unstable, short-lived fibrin clots ultimately resulting in an overall anticoagulant effect due to fibrinogen depletion. The monovalent antivenom 'Thai Red Cross Green Pit Viper antivenin', varied in efficacy ranging from excellent neutralisation of T. albolabris venom through to T. gumprechti and T. mcgregori being poorly neutralised and T. hageni being unrecognised by the antivenom. While the results showing excellent neutralisation of some non-T. albolabris venoms (such as T. flavomaculaturs, T. fucatus, and T. macrops) needs to be confirmed with in vivo tests, conversely the antivenom failure T. hageni, and the very poor results against T. gumprechti and T. mcgregori, despite being conducted in the ideal scenario of preincubation of antivenom:venom, indicates that the likelihood of clinically relevant cross-reactivity for these species is low (T. gumprechti and T. mcgregori) to non-existent (T. hageni). These same latter three species were also not inhibited by the serine protease inhibitor AEBSF, suggesting that the toxins leading to a coagulotoxic effect in these species are non-serine proteases while in contrast T. albolabris coagulotoxicity was completely impeded by AEBSF, and thus driven by kallikrein-type serine proteases. There was a conspicuous lack of phylogenetic pattern in venom variation, with the most potent venoms (T. albolabris and T. hageni) being distant to each other on the organismal tree, and with the three most divergent and poorly neutralised venoms (T. gumprechti, T. hageni, and T. mcgregori) were also not each others closest relatives. This reinforces the paradigm that the fundamental dynamic evolution of venom results in organismal phylogeny being a poor predictor of venom potency or antivenom efficacy. This study provides a robust investigation on the differential venom effects from a wide range of Trimeresurus species on coagulation, highlighting differential fibrinogenolytic effects, while also investigating the relative antivenom neutralisation capabilities of the widely available Thai Red Cross Green Pit Viper antivenom. These results therefore have immediate, real-world implications for patients envenomed by Trimeresurus species.

Agkihpin, a Distinct SVTLE from the Venom of Gloydius halys Pallas: Purification, Characterization and Structure-Activity Determination

Blood clots produced by snake-venom thrombin-like enzymes (SVTLEs) are cleared rapidly, which makes SVTLEs attractive as potential candidates for antithrombotic therapy. We isolated a SVTLE, agkihpin, from the venom of Gloydius halys Pallas. Agkihpin was confirmed to a single-chain TLE with molecular mass of 25.5 kD, pI of 7.43, optimal pH of 8.0 (hydrolyzing TAME), linked carbohydrate absent, and weak fibrinogen clotting activity. It was also found that (i) G. halys might be the latest species in SVTLEs phylogenetic tree; (ii) different level of conservation was shown among the SVTLEs from the Viperidae snakes. Some of those site may account for different activities exhibited by those SVTLEs, especially position 181, at which a fibrinogenolytic activity increase was found when a basic and larger amino acid substituted by a neutral and smaller one; (iii) an extra α-helix constructed with a 'Pro + acidic amino acid + aromatic amino acid' pattern was found in the SVTLEs from Gloydius and Agkistrodon snakes, although it does not necessarily imply an effect on the fibrinogenolytic activity of the SVTLEs. This study provided some new insight into the activity of SVTLE.

Animal Toxins as Therapeutic Tools to Treat Neurodegenerative Diseases

Neurodegenerative diseases affect millions of individuals worldwide. So far, no disease-modifying drug is available to treat patients, making the search for effective drugs an urgent need. Neurodegeneration is triggered by the activation of several cellular processes, including oxidative stress, mitochondrial impairment, neuroinflammation, aging, aggregate formation, glutamatergic excitotoxicity, and apoptosis. Therefore, many research groups aim to identify drugs that may inhibit one or more of these events leading to neuronal cell death. Venoms are fruitful natural sources of new molecules, which have been relentlessly enhanced by evolution through natural selection. Several studies indicate that venom components can exhibit selectivity and affinity for a wide variety of targets in mammalian systems. For instance, an expressive number of natural peptides identified in venoms from animals, such as snakes, scorpions, bees, and spiders, were shown to lessen inflammation, regulate glutamate release, modify neurotransmitter levels, block ion channel activation, decrease the number of protein aggregates, and increase the levels of neuroprotective factors. Thus, these venom components hold potential as therapeutic tools to slow or even halt neurodegeneration. However, there are many technological issues to overcome, as venom peptides are hard to obtain and characterize and the amount obtained from natural sources is insufficient to perform all the necessary experiments and tests. Fortunately, technological improvements regarding heterologous protein expression, as well as peptide chemical synthesis will help to provide enough quantities and allow chemical and pharmacological enhancements of these natural occurring compounds. Thus, the main focus of this review is to highlight the most promising studies evaluating animal toxins as therapeutic tools to treat a wide variety of neurodegenerative conditions, including Alzheimer's disease, Parkinson's disease, brain ischemia, glaucoma, amyotrophic lateral sclerosis, and multiple sclerosis.

Hemocoagulase might not control but worsen gastrointestinal bleeding in an elderly patient with type II respiratory failure

Hemocoagulase has been successfully used for the management of bleeding in patients undergoing surgery. Local spray of hemocoagulase during endoscopic therapy may be effective for the management of gastrointestinal bleeding. In China, intravenous infusion of hemocoagulase is given by some physicians for the treatment of gastrointestinal bleeding. However, the potential adverse events secondary to hemocoagulase, such as hypofibrinogenemia, are poorly recognized. In this paper, we reported an elderly patient with type II respiratory failure in whom hemocoagulase might induce hypofibrinogenemia and further worsen gastrointestinal bleeding. We highlighted that fibrinogen levels should be cautiously monitored in patients receiving hemocoagulase.

Ancrod revisited: viscoelastic analyses of the effects of Calloselasma rhodostoma venom on plasma coagulation and fibrinolysis

Fibrinogen depletion via catalysis by snake venom enzymes as a therapeutic strategy to prevent or treat thrombotic disorders was utilized for over four decades, with ancrod being the quintessential agent. However, ancrod eventually was found to not be of clinical utility in large scale stroke trial, resulting in the eventual discontinuation of the administration of the drug for any indication. It was hypothesized that ancrod, possessing thrombin-like activity, may have unappreciated robust coagulation kinetics. Using thrombelastographic methods, a comparison of equivalent tissue factor initiated thrombin generation and Calloselasma rhodostoma venom (rich in ancrod activity) on plasmatic coagulation kinetics was performed. The venom resulted in thrombi that formed nearly twice as fast compared to thrombin formed clots, and there was no difference in fibrinolytic kinetics initiated by tissue-type plasminogen activator. In plasma containing iron and carbon monoxide modified fibrinogen, which may be found in patients at risk of stroke, the coagulation kinetic differences observed with venom was still more vigorous than that seen with thrombin. These phenomena may provide insight into the clinical failure of ancrod, and may serve as an impetus to revisit the concept of fibrinogen depletion via fibrinogenolytic enzymes, not those with thrombin-like activity.

Iron and carbon monoxide attenuate degradation of plasmatic coagulation by Crotalus atrox venom

Hypofibrinogenemia is an important clinical consequence following envenomation by Crotalus species, usually attenuated or prevented by administration of antivenom. It has been determined that iron and carbon monoxide (CO) enhance fibrinogen as a thrombin substrate, likely secondary to conformational changes in molecular structure. We tested the hypothesis that pretreatment of plasma with iron and CO could attenuate the effects of exposure to Crotalus atrox venom. Human plasma was exposed to 0 to 10 μmol/l ferric chloride (iron source) and 0 to 100 μmol/l CO-releasing molecule-2 (CO source) followed by exposure to 0 to 0.5 μg/ml venom for 5 to 20 min. Changes in coagulation kinetics were determined with thrombelastography. Iron and CO significantly attenuated venom-mediated degradation of plasmatic coagulation in terms of onset time, velocity of clot growth and final clot strength. Further preclinical investigation of iron and CO administration as a 'bridge-to-antivenom' to preserve plasmatic coagulation is justified.

Metalloproteases Affecting Blood Coagulation, Fibrinolysis and Platelet Aggregation from Snake Venoms: Definition and Nomenclature of Interaction Sites

Snake venom metalloproteases, in addition to their contribution to the digestion of the prey, affect various physiological functions by cleaving specific proteins. They exhibit their activities through activation of zymogens of coagulation factors, and precursors of integrins or receptors. Based on their structure–function relationships and mechanism of action, we have defined classification and nomenclature of functional sites of proteases. These metalloproteases are useful as research tools and in diagnosis and treatment of various thrombotic and hemostatic conditions. They also contribute to our understanding of molecular details in the activation of specific factors involved in coagulation, platelet aggregation and matrix biology. This review provides a ready reference for metalloproteases that interfere in blood coagulation, fibrinolysis and platelet aggregation.

Protective effects of batroxobin on a nigrostriatal pathway injury in mice

Traumatic brain injury triggers a series of damaged processes, such as neuronal death and apoptosis, inflammation and scar formation, which contribute to evolution of brain injury. The present study investigated the neuroprotective effects of batroxobin, a drug widely used clinically for ischemia, in a nigrostriatal pathway injury model. Mice subjected to the nigrostriatal pathway injury were injected with batroxobin (30 BU/kg) or vehicle immediately after injury. The behavioral studies showed that batroxobin could improve the motor function in injured mice in long term. Batroxobin also reduced neuronal apoptosis and inflammation at the acute stage. Moreover, administration of batroxobin attenuated the scar formation and reduced the lesion size at 4 and 14days after brain injury. These results suggest that batroxobin has beneficial effects on the nigrostriatal pathway injury, indicating a potential clinical application.

Comparative Study of Improvement of Nasal Symptoms Following Septoplasty with Partial Inferior Turbinectomy Versus Septoplasty Alone in Adults by NOSE Scale: A Prospective Study

To compare the symptomatic improvement of nasal symptoms following septoplasty with partial inferior turbinectomy (groups A) versus septoplasty alone (groups B) and to assess the improvement of nasal symptoms in both surgical groups before and after surgery by NOSE scale. This Tertiary Hospital based study was carried out between August 2012 and April 2014. 60 cases with septal deviation and contralateral inferior turbinate hypertrophy. Nasal Obstruction Symptom Evaluation (NOSE) scale for evaluating nasal symptoms. Patients were alternatively divided into two surgical groups, group A. Septoplasty with partial inferior turbinectomy and group B septoplasty alone. Post-operative patient's symptoms evaluated by NOSE scale at 1, 3 and 6 months. Data analysed using tables, graph and percentage and test of significance like paired t test, Friedman test, Chi square test used. Post operative improvement following both group A septoplasty with partial inferior turbinectomy and group B in those undergoing septoplasty alone was highly significant (p < 0.001) at post-op 1, 3 and 6 months subjectively. When both groups were compared those undergoing partial inferior turbinectomy surgery with septoplasty had highly significant results (p < 0.001) for subjective assessment by NOSE scale. This study showed that hypertrophied turbinate need to be addressed in chronic cases of nasal obstruction with deviated nasal septum and contralateral turbinate hypertrophy. partial inferior turbinectomy should be done in addition to septoplasty, its highly effective modality for the treatment of nasal obstruction in patients with deviated nasal septum. NOSE score can be used as a subjective tool for symptomatic measurement of patients with nasal obstruction.

Risk Factors for Postoperative Fibrinogen Deficiency after Surgical Removal of Intracranial Tumors

Higher levels of fibrinogen, a critical element in hemostasis, are associated with increased postoperative survival rates, especially for patients with massive operative blood loss. Fibrinogen deficiency after surgical management of intracranial tumors may result in postoperative intracranial bleeding and severely worsen patient outcomes. However, no previous studies have systematically identified factors associated with postoperative fibrinogen deficiency. In this study, we retrospectively analyzed data from patients who underwent surgical removal of intracranial tumors in Beijing Tiantan Hospital date from 1/1/2013to12/31/2013. The present study found that patients with postoperative fibrinogen deficiency experienced more operative blood loss and a higher rate of postoperative intracranial hematoma, and they were given more blood transfusions, more plasma transfusions, and were administered larger doses of hemocoagulase compared with patients without postoperative fibrinogen deficiency. Likewise, patients with postoperative fibrinogen deficiency had poorer extended Glasgow Outcome Scale (GOSe), longer hospital stays, and greater hospital expenses than patients without postoperative fibrinogen deficiency. Further, we assessed a comprehensive set of risk factors associated with postoperative fibrinogen deficiency via multiple linear regression. We found that body mass index (BMI), the occurrence of postoperative intracranial hematoma, and administration of hemocoagulasewere positively associated with preoperative-to-postoperative plasma fibrinogen consumption; presenting with a malignant tumor was negatively associated with fibrinogen consumption. Contrary to what might be expected, intraoperative blood loss, the need for blood transfusion, and the need for plasma transfusion were not associated with plasma fibrinogen consumption. Considering our findings together, we concluded that postoperative fibrinogen deficiency is closely associated with postoperative bleeding and poor outcomes and merits careful attention. Practitioners should monitor plasma fibrinogen levels in patients with risk factors for postoperative fibrinogen deficiency. In addition, postoperative fibrinogen deficiency should be remediated as soon as possible to reduce postoperative bleeding, especially when postoperative bleeding is confirmed.

Nanofibrous Snake Venom Hemostat

Controlling perioperative bleeding is of critical importance to minimize hemorrhaging and fatality. Patients on anticoagulant therapy such as heparin have diminished clotting potential and are at risk for hemorrhaging. Here we describe a self-assembling nanofibrous peptide hydrogel (termed SLac) that on its own can act as a physical barrier to blood loss. SLac was loaded with snake-venom derived Batroxobin (50 μg/mL) yielding a drug-loaded hydrogel (SB50). SB50 was potentiated to enhance clotting even in the presence of heparin. In vitro evaluation of fibrin and whole blood clotting helped identify appropriate concentrations for hemostasis in vivo. Batroxobin-loaded hydrogels rapidly (within 20s) stop bleeding in both normal and heparin-treated rats in a lateral liver incision model. Compared to standard of care, Gelfoam, and investigational hemostats such as Puramatrix, only SB50 showed rapid liver incision hemostasis post surgical application. This snake venom-loaded peptide hydrogel can be applied via syringe and conforms to the wound site resulting in hemostasis. This demonstrates a facile method for surgical hemostasis even in the presence of anticoagulant therapies.

Batroxobin protects against spinal cord injury in rats by promoting the expression of vascular endothelial growth factor to reduce apoptosis

The host response to spinal cord injury (SCI) can lead to an ischemic environment that can induce cell death. Therapeutic interventions using neurotrophic factors have focused on the prevention of such reactions in order to reduce this cell death. Vascular endothelial growth factor (VEGF) is a potent angiogenic and vascular permeability factor. We hypothesized in this study that batroxobin would exhibit protective effects following SCI by promoting the expression of VEGF to reduce the levels of apoptosis in a rat model of SCI. Ninety adult female Sprague Dawley rats were divided randomly into sham injury (group I), SCI (group II) and batroxobin treatment (group III) groups. The Basso-Bettie-Bresnahan (BBB) scores, number of apoptotic cells and expression of VEGF were assessed at 1, 3, 5, 7, 14 and 28 days post-injury. The BBB scores were significantly improved in group III compared with those in group II between days 5 and 28 post-injury (P<0.05). At each time-point subsequent to the injury, the number of apoptotic cells in group III was reduced compared with that in group II. Compared with group II, treatment with batroxobin significantly increased the expression of VEGF from day 3 until 2 weeks post-SCI (P<0.05), while no significant difference was observed at day 28. These data suggest that batroxobin has multiple beneficial effects on SCI, indicating a potential clinical application.

Effects of botropase on clotting factors in healthy human volunteers

OBJECTIVE

To evaluate the effects of botropase on various clotting factors in human volunteers.

MATERIALS AND METHODS

It was a prospective open label study conducted on human healthy volunteers. After the baseline screening, subjects fulfilling inclusion criteria were enrolled. On the study day, 1 ml of botropase was administered intravenously and after an hour same dose of botropase (1 ml) was given by intramuscular (IM) route. The efficacy and safety parameters were monitored up to 72 h from the time of intravenous (IV) administration.

RESULTS

A total of 15 volunteers, belonging to 24-35 years of age were included in the study. Botropase significantly reduced the plasma level of fibrinogen and fibrin degradation products after 5 min of IV administration (P < 0.05). In addition, factor X was observed to reduce constantly by botropase administration suggesting enhanced turnover between 5 and 20 min of IV administration. Although botropase reduced clotting and bleeding time in all the volunteers, the data remains to be statistically insignificant.

CONCLUSION

Present study demonstrated the safety and efficacy of botropase in human healthy volunteers. The study has shown that it is a factor X activator and reduces effectively clotting and bleeding time.

A comprehensive mechanism of fibrin network formation involving early branching and delayed single- to double-strand transition from coupled time-resolved X-ray/light-scattering detection

The formation of a fibrin network following fibrinogen enzymatic activation is the central event in blood coagulation and has important biomedical and biotechnological implications. A non-covalent polymerization reaction between macromolecular monomers, it consists basically of two complementary processes: elongation/branching generates an interconnected 3D scaffold of relatively thin fibrils, and cooperative lateral aggregation thickens them more than 10-fold. We have studied the early stages up to the gel point by fast fibrinogen:enzyme mixing experiments using simultaneous small-angle X-ray scattering and wide-angle, multi-angle light scattering detection. The coupled evolutions of the average molecular weight, size, and cross section of the solutes during the fibrils growth phase were thus recovered. They reveal that extended structures, thinner than those predicted by the classic half-staggered, double-stranded mechanism, must quickly form. Following extensive modeling, an initial phase is proposed in which single-bonded "Y-ladder" polymers rapidly elongate before undergoing a delayed transition to the double-stranded fibrils. Consistent with the data, this alternative mechanism can intrinsically generate frequent, random branching points in each growing fibril. The model predicts that, as a consequence, some branches in these expanding "lumps" eventually interconnect, forming the pervasive 3D network. While still growing, other branches will then undergo a Ca(2+)/length-dependent cooperative collapse on the resulting network scaffolding filaments, explaining their sudden thickening, low final density, and basic mechanical properties.

Snake bites and hemostasis/thrombosis

Snake venom toxins have evolved to affect many prey physiological systems including hemostasis and thrombosis. These toxins belong to a diverse array of protein families and can initiate or inhibit multiple stages of the coagulation pathway or platelet aggregation with incredible specificity. Such specificity toward vertebrate molecular targets has made them extremely useful for diagnosis of human diseases or as molecular scalpels in physiological studies. The large number of yet-to-be characterized venoms provides a vast potential source of novel toxins and subsequent cardiovascular therapeutics and diagnostic agents.

Protective effects of Batroxobin on spinal cord injury in rats

Expansion of the secondary injury following primary spinal cord injury is a major pathological event that increases destruction in the spinal cord, so measures to reduce secondary injury are needed. Our previous study demonstrated that, at the front of the expanding secondary injury in the spinal cord, there is an ischemic area in which many neurons can still be rescued. Therefore, enhancement of blood circulation in the cord may be helpful, and indeed, we found that a traditional Chinese medicine, shu-xue-tong, efficiently reduces the secondary injury. The aim of the present study was to investigate the effect of reducing fibrinogen with Batroxobin, a drug widely used clinically for ischemia, in rats with spinal cord contusion. We found that both 2 and 4 Batroxobin units (BU)/kg efficiently decreased the plasma fibrinogen, and 2 BU/kg significantly increased spinal blood flow, enhanced neuronal survival, mitigated astrocyte and microglia activation, and improved locomotor recovery. However, 4 BU/kg had no effect on the secondary spinal cord injury. These data suggest that Batroxobin has multiple beneficial effects on spinal cord injury, indicating a potential clinical application.

Plasminogen activators and ischemic stroke: conditions for acute delivery

Appropriate acute treatment with plasminogen activators (PAs) can significantly increase the probability of minimal or no disability in selected ischemic stroke patients. There is a great deal of evidence showing that intravenous recombinant tissue PAs (rt-PA) infusion accomplishes this goal, recanalization with other PAs has also been demonstrated in the development of this treatment. Recanalization of symptomatic, documented carotid or vertebrobasilar arterial territory occlusions have also been achieved by local intra-arterial PA delivery, although only a single prospective double-blinded randomized placebo-controlled study has been reported. The increase in intracerebral hemorrhage with these agents by either delivery approach underscores the need for careful patient selection, dose-appropriate safety and efficacy, proper clinical trial design, and an understanding of the evolution of cerebral tissue injury due to focal ischemia. Principles underlying the evolution of focal ischemia have been expanded by experience with acute PA intervention. Several questions remain open that concern the manner in which PAs can be applied acutely in ischemic stroke and how injury development can be limited.

Coagulant thrombin-like enzyme (barnettobin) from Bothrops barnetti venom: molecular sequence analysis of its cDNA and biochemical properties

The thrombin-like enzyme from Bothrops barnetti named barnettobin was purified. We report some biochemical features of barnettobin including the complete amino acid sequence that was deduced from the cDNA. Snake venom serine proteases affect several steps of human hemostasis ranging from the blood coagulation cascade to platelet function. Barnettobin is a monomeric glycoprotein of 52 kDa as shown by reducing SDS-PAGE, and contains approx. 52% carbohydrate by mass which could be removed by N-glycosidase. The complete amino acid sequence was deduced from the cDNA sequence. Its sequence contains a single chain of 233 amino acid including three N-glycosylation sites. The sequence exhibits significant homology with those of mammalian serine proteases e.g. thrombin and with homologous TLEs. Its specific coagulant activity was 251.7 NIH thrombin units/mg, releasing fibrinopeptide A from human fibrinogen and showed defibrinogenating effect in mouse. Both coagulant and amidolytic activities were inhibited by PMSF. N-deglycosylation impaired its temperature and pH stability. Its cDNA sequence with 750 bp encodes a protein of 233 residues. Indications that carbohydrate moieties may play a role in the interaction with substrates are presented. Barnettobin is a new defibrinogenating agent which may provide an opportunity for the development of new types of anti-thrombotic drugs.

Herpetofauna Used in Traditional Folk Medicine: Conservation Implications

This chapter provides an overview of the global use of herpetofauna in traditional folk medicine and the implications for conservation. The results indicate that 331 species (284 reptiles and 47 amphibians) are used in traditional folk medicine around the world. Among the species recorded, 182 reptiles and 42 amphibians are listed in the IUCN Red List. Additionally, 93 reptiles are in some of the appendices of CITES. These numbers demonstrate the importance of understanding such medicinal uses in the context of reptile conservation as well as the need for considering sociocultural factors when establishing management plans directed toward the sustainable use of these reptiles.

The first report on the medicinal use of fossils in latin america

There have been very few ethnopharmacological studies performed on the traditional use of fossil species, although a few records have been conducted in Asia, Africa, and Europe. This study is the first ever to be performed on the use of Testudine (turtle) fossils for folk medicine in Latin America. An investigation was conducted in the Araripe Basin, which is one of the most important fossil-bearing reserves in the world due to the diversity, endemism, and quality of preservation of its fossils. We propose the formalization of a new discipline called ethnopaleontology, which will involve the study of the dynamic relationship between humans and fossils, from human perception to direct use.

Structure of saxthrombin, a thrombin-like enzyme from Gloydius saxatilis

Snake-venom thrombin-like enzymes (SVTLEs) are serine proteases that are widely distributed in snakes from the Crotalinae subfamily of the Viperidae. In contrast to other snake-venom serine proteases, they have a biochemical activity similar to that of thrombin and play an important role in the process of blood coagulation. However, SVTLEs cannot activate factor VIII, which is essential in blood-clot stabilization. Consequently, blood clots produced by SVTLEs are not stable and are cleared rapidly. This characteristic makes SVTLEs attractive as potential candidates for antithrombotic therapy. Saxthrombin, an SVTLE from Gloydius saxatilis, was purified and crystallized to obtain a high-quality crystal, from which data were acquired to 1.43 Å resolution. Preliminary X-ray diffraction analysis showed that the crystal belonged to space group C2, with unit-cell parameters a = 94.2, b = 52.2, c = 50.1 Å, β = 96.7°. The crystal structure was determined by molecular replacement and the final R factor was 18.69%; the R(free) was 20.01%. This is the first report of a crystal structure of an SVTLE. Saxthrombin belongs to the typical α/β-hydrolase fold of serine proteases. Its structure was compared with those of thrombin and other snake-venom serine proteases. The observed differences in the amino-acid composition of the loops surrounding the active site appear to contribute to different surface-charge distributions and thus alter the shape of the active-site cleft, which may explain the differences in substrate affinity.

Comparative study of anticoagulant and procoagulant properties of 28 snake venoms from families Elapidae, Viperidae, and purified Russell's viper venom-factor X activator (RVV-X)

Snake venoms consist of numerous molecules with diverse biological functions used for capturing prey. Each component of venom has a specific target, and alters the biological function of its target. Once these molecules are identified, characterized, and cloned; they could have medical applications. The activated clotting time (ACT) and clot rate were used for screening procoagulant and anticoagulant properties of 28 snake venoms. Crude venoms from Daboia russellii siamensis, Bothrops asper, Bothrops moojeni, and one Crotalus oreganus helleri from Wrightwood, CA, had procoagulant activity. These venoms induced a significant shortening of the ACT and showed a significant increase in the clot rate when compared to the negative control. Factor X activator activity was also measured in 28 venoms, and D. r. siamensis venom was 5-6 times higher than those of B. asper, B. moojeni, and C. o. helleri from Wrightwood County. Russell's viper venom-factor X activator (RVV-X) was purified from D. r. siamensis venom, and then procoagulant activity was evaluated by the ACT and clot rate. Other venoms, Crotalus atrox and two Naja pallida, had anticoagulant activity. A significant increase in the ACT and a significant decrease in the clot rate were observed after the addition of these venoms; therefore, the venoms were considered to have anticoagulant activity. Venoms from the same species did not always have the same ACT and clot rate profiles, but the profiles were an excellent way to identify procoagulant and anticoagulant activities in snake venoms.

Platelet-active substances in the venom of Bothrops moojeni snake-a novel evaluation method using whole blood aggregometry

The objective of the present study was an investigation of the crude Bothrops moojeni venom, aiming at the identification of new compounds with platelet-activating or -inhibiting activity. The venom was separated by gel filtration chromatography into 18 fractions, which were tested by means of whole blood aggregometry for their activities affecting the aggregation of blood platelets. In order to eliminate interferences caused by prothrombin activators or thrombin like-enzymes, which are frequently present in snake venoms, a test method for screening protein mixtures was developed. To avoid clotting of the blood samples, the thrombin inhibitor hirudin and the synthetic inhibitor of fibrin polymerization Pefabloc FG were applied. In the present study, a platelet aggregation activator with an activity resembling thrombocytin from B. atrox was identified in one of the examined venom fractions. In addition, a platelet antagonist-most likely a disintegrin-with broad inhibitory activity against aggregation triggered by collagen, adenosine diphosphate and thrombin receptor activating peptide, was identified.

Functional and structural analysis of two fibrinogen-activating enzymes isolated from the venoms of Crotalus durissus terrificus and Crotalus durissus collilineatus

Fibrinogen-activating enzymes, widely distributed in Crotalidae and Viperidae venoms, are single-chain glycosylated serine proteases that display high macromolecular selectivity and are often referred to as thrombin-like enzymes (TLEs). TLEs serve as structural models to extend our understanding of the structure-function relationships of blood coagulation factors, have been clinically used for the treatment of thrombotic diseases, and are used as tools in clinical assays. The combination of gel filtration and ion-exchange chromatography proved to be successful in obtaining milligram quantities of pure samples of TLEs from the venoms of Crotalus durissus terrificus (white venom) and Crotalus durissus collilineatus (yellow venom). Functional characterization indicates that both enzymes preferentially degrade the Bb chain of bovine fibrinogen and possess edema-inducing and coagulant activities. However, the TLE from C. d. collilineatus venom shows twofold higher coagulant activity with a minimum coagulant dose (MCD) of 0.6 microg/microl, whereas the enzyme isolated from C. d. terrificus indicated an MCD of 1.5 microg/microl. Molecular modeling of gyroxin and structural comparisons with other highly conserved snake venom serine proteases, underlines the key role played by the surface charge distribution and the double insertion in the 174-surface loop in macromolecular substrate recognition by TLEs.

Quantitative analysis of snake venoms using soluble polymer-based isotope labeling

We present the design and synthesis of a new quantitative strategy termed soluble polymer-based isotope labeling (SoPIL) and its application as a novel and inclusive method for the identification and relative quantification of individual proteins in complex snake venoms. The SoPIL reagent selectively captures and isolates cysteine-containing peptides, and the subsequent tagged peptides are released and analyzed using nanoflow liquid chromatography-tandem mass spectrometry. The SoPIL strategy was used to quantify venom proteins from two pairs of venomous snakes: Crotalus scutulatus scutulatus type A, C. scutulatus scutulatus type B, Crotalus oreganus helleri, and Bothrops colombiensis. The hemorrhagic, hemolytic, clotting ability, and fibrinogenolytic activities of crude venoms were measured and correlated with difference in protein abundance determined by the SoPIL analysis. The SoPIL approach could provide an efficient and widely applicable tool for quantitative proteomics.

Venom therapy in multiple sclerosis

To date many people with multiple sclerosis (MS) seek complementary and alternative medicines (CAM) to treat their symptoms as an adjunct to conventionally used therapies. Among the common CAM therapies, there is a renewed interest in the therapeutic potential of venoms in MS. The efficacy of this therapeutic method remains unclear. However, venom-based therapy using bee, snakes and scorpions venom and/or sea anemones toxin has been recently developed because current investigations have identified the various components and molecular mechanism of the effects of venoms under in vitro and in vivo conditions. The aim of this review is to describe the recent findings regarding the role of venoms and their components in treatment of MS disease and that whether venom therapy could be recommended as a complementary treatment or not.

Anticoagulant proteins from snake venoms: structure, function and mechanism

Over the last several decades, research on snake venom toxins has provided not only new tools to decipher molecular details of various physiological processes, but also inspiration to design and develop a number of therapeutic agents. Blood circulation, particularly thrombosis and haemostasis, is one of the major targets of several snake venom proteins. Among them, anticoagulant proteins have contributed to our understanding of molecular mechanisms of blood coagulation and have provided potential new leads for the development of drugs to treat or to prevent unwanted clot formation. Some of these anticoagulants exhibit various enzymatic activities whereas others do not. They interfere in normal blood coagulation by different mechanisms. Although significant progress has been made in understanding the structure-function relationships and the mechanisms of some of these anticoagulants, there are still a number of questions to be answered as more new anticoagulants are being discovered. Such studies contribute to our fight against unwanted clot formation, which leads to death and debilitation in cardiac arrest and stroke in patients with cardiovascular and cerebrovascular diseases, arteriosclerosis and hypertension. This review describes the details of the structure, mechanism and structure-function relationships of anticoagulant proteins from snake venoms.

Serine proteases affecting blood coagulation and fibrinolysis from snake venoms

Snake venom proteases, in addition to their contribution to the digestion of the prey, affect various physiological functions. They affect platelet aggregation, blood coagulation, fibrinolysis, complement system, blood pressure and nervous system. This review provides a ready reference for serine proteases that interfere in blood coagulation and fibrinolysis. They exhibit their activity by activation of specific zymogens of coagulation factors. These serine proteases serve as tools to study molecular details in the activation of specific factors involved in coagulation and fibrinolytic cascades and are useful in treating various thrombotic and hemostatic conditions.

A catalog for the transcripts from the venomous structures of the caterpillar Lonomia obliqua: identification of the proteins potentially involved in the coagulation disorder and hemorrhagic syndrome

Accidents with the caterpillar Lonomia obliqua are often associated with a coagulation disorder and hemorrhagic syndrome in humans. In the present study, we have constructed cDNA libraries from two venomous structures of the caterpillar, namely the tegument and the bristle. High-throughput sequencing and bioinformatics analyses were performed in parallel. Over one thousand cDNAs were obtained and clustered to produce a database of 538 contigs and singletons (clusters) for the tegument library and 368 for the bristle library. We have thus identified dozens of full-length cDNAs coding for proteins with sequence homology to snake venom prothrombin activator, trypsin-like enzymes, blood coagulation factors and prophenoloxidase cascade activators. We also report cDNA coding for cysteine proteases, Group III phospholipase A2, C-type lectins, lipocalins, in addition to protease inhibitors including serpins, Kazal-type inhibitors, cystatins and trypsin inhibitor-like molecules. Antibacterial proteins and housekeeping genes are also described. A significant number of sequences were devoid of database matches, suggesting that their biologic function remains to be defined. We also report the N-terminus of the most abundant proteins present in the bristle, tegument, hemolymph, and "cryosecretion". Thus, we have created a catalog that contains the predicted molecular weight, isoelectric point, accession number, and putative function for each selected molecule from the venomous structures of L. obliqua. The role of these molecules in the coagulation disorder and hemorrhagic syndrome caused by envenomation with this caterpillar is discussed. All sequence information and the , including figures and tables with hyperlinks to FASTA-formatted files for each contig and the best match to the databases, are available at http://www.ncbi.nih.gov/projects/omes.

Snake venom serine proteinases: sequence homology vs. substrate specificity, a paradox to be solved

Snake venom glands synthesize a variety of serine proteinases capable of affecting the haemostatic system. They act on macromolecular substrates of the coagulation, fibrinolytic, and kallikrein-kinin systems, and on platelets to cause an imbalance of the haemostatic system of the prey. In this review we describe their biochemical/biophysical characteristics, biological activities as well as aspects of their evolution and structure-activity relationship.