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

Biochemical and hemostatic description of a thrombin-like enzyme TLBro from Bothrops roedingeri snake venom

Objective: The current study's objective is to characterize a new throm-bin-like enzyme called TLBro that was obtained from Bothrops roedingeris snake from a biochemical and hemostatic perspective. Methodology: One chromatographic step was used to purify it, producing the serine protease TLBro. Molecular mass was estimated by SDS-PAGE to be between reduced and unreduced by 35 kDa. Tryptic peptide sequencing using Swiss Prot provided the complete amino acid sequence. Expasy.org by conducting a search that is limited to Crotalinae snake serine proteases and displaying a high degree of amino acid sequence. Results: Ser (182) is inhibited by phenylmethylsulfonyl fluoride (PMSF), and TLBro demonstrated the presence of Asp (88) residues. It also deduced the positions of His (43) and Ser (182) in the set of three coordinated amino acids in serine proteases. It was discovered that this substrate had high specificity for BANA, Michaelis-Menten behavior with KM 0 point85 mM and Vmax 1 point89 nmoles -NA/L/min, and high stability between temperatures (15 to 70°C) and pHs (2 point0 to 10 point0). According to doses and incubation times, TLBro degraded fibrin preferentially on the B-chain; additionally, its activities were significantly diminished after preincubation with divalent ions (Zn2 and Cd2). When incubated with PMSF, a particular serine protease inhibitor, enzymatic activities and platelet aggregation were inhibited. Conclusion: The findings revealed distinct structural and functional differences between the serine proteases, adding to the information and assisting in the improvement of the structure-function relationship.

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.

Isolation and Characterization of Poeciguamerin, a Peptide with Dual Analgesic and Anti-Thrombotic Activity from the Poecilobdella manillensis Leech

When Poecilobdella manillensis attacks its prey, the prey bleeds profusely but feels little pain. We and other research teams have identified several anticoagulant molecules in the saliva of P. manillensis, but the substance that produces the paralyzing effect in P. manillensis is not known. In this study, we successfully isolated, purified, and identified a serine protease inhibitor containing an antistasin-like domain from the salivary secretions of P. manillensis. This peptide (named poeciguamerin) significantly inhibited elastase activity and slightly inhibited FXIIa and kallikrein activity, but had no effect on FXa, trypsin, or thrombin activity. Furthermore, poeciguamerin exhibited analgesic activity in the foot-licking and tail-withdrawal mouse models and anticoagulant activity in the FeCl₃-induced carotid artery thrombosis mouse model. In this study, poeciguamerin was found to be a promising elastase inhibitor with potent analgesic and antithrombotic activity for the inhibition of pain and thrombosis after surgery or in inflammatory conditions.

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.

Clinical and Evolutionary Implications of Dynamic Coagulotoxicity Divergences in Bothrops (Lancehead Pit Viper) Venoms

Despite coagulotoxicity being a primary weapon for prey capture by Bothrops species (lancehead pit vipers) and coagulopathy being a major lethal clinical effect, a genus-wide comparison has not been undertaken. To fill this knowledge gap, we used thromboelastography to compare 37 venoms, from across the full range of geography, taxonomy, and ecology, for their action upon whole plasma and isolated fibrinogen. Potent procoagulant toxicity was shown to be the main venom effect of most of the species tested. However, the most basal species (B. pictus) was strongly anticoagulant; this is consistent with procoagulant toxicity being a novel trait that evolved within Bothrops subsequent to their split from anticoagulant American pit vipers. Intriguingly, two of the arboreal species studied (B. bilineatus and B. taeniatus) lacked procoagulant venom, suggesting differential evolutionary selection pressures. Notably, some terrestrial species have secondarily lost the procoagulant venom trait: the Mogi Mirim, Brazil locality of B. alternatus; San Andres, Mexico locality of B. asper; B. diporus; and the São Roque of B. jararaca. Direct action on fibrinogen was extremely variable; this is consistent with previous hypotheses regarding it being evolutionary decoupled due to procoagulant toxicity being the primary prey-capture weapon. However, human patients live long enough for fibrinogen depletion to be clinically significant. The extreme variability may be reflective of antivenom variability, with these results thereby providing a foundation for such future work of clinical relevance. Similarly, the venom diversification trends relative to ecological niche will also be useful for integration with natural history data, to reconstruct the evolutionary pressures shaping the venoms of these fascinating snakes.

A fingerprint of plasma proteome alteration after local tissue damage induced by Bothrops leucurus snake venom in mice

Bothrops spp. is responsible for about 70% of snakebites in Brazil, causing a diverse and complex pathophysiological condition. Bothrops leucurus is the main species of medical relevance found in the Atlantic coast in the Brazilian Northeast region. The pathophysiological effects involved B. leucurus snakebite as well as the organism's reaction in response to this envenoming, it has not been explored yet. Thus, edema was induced in mice paw using 1.2, 2.5, and 5.0 μg of B. leucurus venom, the percentage of edema was measured 30 min after injection and the blood plasma was collected and analyzed by shotgun proteomic strategy. We identified 80 common plasma proteins with differential abundance among the experimental groups and we can understand the early aspects of this snake envenomation, regardless of the suggestive severity of an ophidian accident. The results showed B. leucurus venom triggers a thromboinflammation scenario where family's proteins of the Serpins, Apolipoproteins, Complement factors and Component subunits, Cathepsins, Kinases, Oxidoreductases, Proteases inhibitors, Proteases, Collagens, Growth factors are related to inflammation, complement and coagulation systems, modulators platelets and neutrophils, lipid and retinoid metabolism, oxidative stress and tissue repair. Our findings set precedents for future studies in the area of early diagnosis and/or treatment of snakebites. SIGNIFICANCE: The physiopathological effects that the snake venoms can cause have been investigated through classical and reductionist tools, which allowed, so far, the identification of action mechanisms of individual components associated with specific tissue damage. The currently incomplete limitations of this knowledge must be expanded through new approaches, such as proteomics, which may represent a big leap in understanding the venom-modulated pathological process. The exploration of the complete protein set that suffer modifications by the simultaneous action of multiple toxins, provides a map of the establishment of physiopathological phenotypes, which favors the identification of multiple toxin targets, that may or may not act in synergy, as well as favoring the discovery of biomarkers and therapeutic targets for manifestations that are not neutralized by the antivenom.

Shrew's venom quickly causes circulation disorder, analgesia and hypokinesia

Multiple representatives of eulipotyphlan mammals such as shrews have oral venom systems. Venom facilitates shrews to hunt and/or hoard preys. However, little is known about their venom composition, and especially the mechanism to hoard prey in comatose states for meeting their extremely high metabolic rates. A toxin (BQTX) was identified from venomous submaxillary glands of the shrew Blarinella quadraticauda. BQTX is specifically distributed and highly concentrated (~ 1% total protein) in the organs. BQTX shares structural and functional similarities to toxins from snakes, wasps and snails, suggesting an evolutional relevancy of venoms from mammalians and non-mammalians. By potentiating thrombin and factor-XIIa and inhibiting plasmin, BQTX induces acute hypertension, blood coagulation and hypokinesia. It also shows strong analgesic function by inhibiting elastase. Notably, the toxin keeps high plasma stability with a 16-h half-life in-vivo, which likely extends intoxication to paralyze or immobilize prey hoarded fresh for later consumption and maximize foraging profit.

Bioactive Molecules Derived from Snake Venoms with Therapeutic Potential for the Treatment of Thrombo-Cardiovascular Disorders Associated with COVID-19

As expected, several new variants of Severe Acute Respiratory Syndrome-CoronaVirus-2 (SARS-CoV-2) emerged and have been detected around the world throughout this Coronavirus Disease of 2019 (COVID-19) pandemic. Currently, there is no specific developed drug against COVID-19 and the challenge of developing effective antiviral strategies based on natural agents with different mechanisms of action becomes an urgent need and requires identification of genetic differences among variants. Such data is used to improve therapeutics to combat SARS-CoV-2 variants. Nature is known to offer many biotherapeutics from animal venoms, algae and plant that have been historically used in traditional medicine. Among these bioresources, snake venom displays many bioactivities of interest such as antiviral, antiplatelet, antithrombotic, anti-inflammatory, antimicrobial and antitumoral. COVID-19 is a viral respiratory sickness due to SARS-CoV-2 which induces thrombotic disorders due to cytokine storm, platelet hyperactivation and endothelial dysfunction. This review aims to: (1) present an overview on the infection, the developed thrombo-inflammatory responses and mechanisms of induced thrombosis of COVID-19 compared to other similar pathogenesis; (2) underline the role of natural compounds such as anticoagulant, antiplatelet and thrombolytic agents; (3) investigate the management of coagulopathy related to COVID-19 and provide insight on therapeutic such as venom compounds. We also summarize the updated advances on antiviral proteins and peptides derived from snake venoms that could weaken coagulopathy characterizing COVID-19.

Hesperetin as an inhibitor of the snake venom serine protease from Bothrops jararaca

The majority (90%) of the snakebite envenomation in Brazil accounts for Bothrops from the Viperidae family. Some snake venom serine proteases provoke blood coagulation in ophidian accident victims because of their fibrinolytic activity, one of those proteases from Bothrops jararaca (B. jararaca) has been chosen for this study. Our objectives were to isolate and characterize the target serine protease; isolate, purify, and characterize the orange bagasse flavone (hesperetin, Hst), and investigate the interactions between the targets, enzyme, and hesperetin. The purified serine protease was named BjSP24 because of its molecular mass and proteolytic activity. BjSP24 was folded and characterized using circular dichroism and showed low alpha-helix contents (7.7%). BjSP24 exhibited sequence similarity to other known snake venom serine proteases as measured in the enzyme tryptic peptides' LC-MS/MS run. Hesperetin was obtained within the expected yield and with the predominance of 2S isomer (82%). It acted as a mixed inhibitor for the serine protease (SVSP) from Bothrops jararaca snake venom observed in three different in vitro experiments, fluorescence, kinetics, and SSTD-NMR. It is still to determine if hesperetin might aid-in reverting the on site blood clotting problems just after snakebite accidents.

Purification, characterization and fibrino(geno)lytic activity of cysteine protease from Tabernaemontana divaricata latex

Protease was isolated and purified from Tabernaemontana divaricata latex and its hemostatic potential was analyzed. Crude latex enzyme was purified through ion exchange and gel filtration chromatography. Purified protease was characterized and its thrombin-like (coagulant assay, fibrinogen polymerizing, and fibrinogenolytic activity) and plasmin-like (blood and plasma clot lysis) activities were assessed accordingly. The homogeneous nature of protease was confirmed with the identification of a single band approximately at 25-kDa molecular weight position. The purified enzyme showed an enhancement of 77.32% in clot inducing ability and 89.86% improvement in blood clot lysis in comparison to that by the crude enzyme. All three subunits (Aα, Bβ and γ chains) of human fibrinogen were hydrolyzed by the purified enzyme. PAGE results of the fibrinolytic activity and blood clot lytic effect by the purified enzyme indicated the plasmin-like activity. The study lays a foundation for the development of enzyme-based approaches for pharmaceutical innovations, in which plant latex proteases can be utilized as a potential natural agent for wound healing applications.

Bothrops leucurus venom induces acute hypotension in rats by means of its phospholipase A2 (blD-PLA2)

Cardiovascular effects induced by snake venoms, in spite of having a crucial role in the outcome of the envenomation, have been less studied than other toxic activities displayed by these venoms. In this study we evaluated acute cardiovascular responses to Bothrops leucurus venom - Bl-V - both in vivo, in anesthetized rats, and in vitro, in isolated rat mesenteric resistance arteries. Bl-V (10-100 μg protein/kg) caused dose-dependent hypotension, followed by gradual recovery (2-20 min) to basal levels, and induced dose-dependent (1-20 μg/mL) vasodilation in pre-contracted arteries, what was more pronounced when the endothelium remained intact. These effects were partially counteracted by pre-treatment with indomethacin (cyclooxygenase inhibitor). Prior incubation of Bl-V with commercial pentavalent Bothrops antivenom also attenuated the cardiovascular effects induced by the venom, in spite of it not being among the venoms used for the development of the bothropic antivenom. Through an approach based on two chromatographic steps and mass spectrometry (MALDI-ToF and MALDI-ISD), a component with acute cardiovascular effects was isolated and identified as the basic phospholipase blD-PLA₂, previously purified from the venom of B. leucurus. Taken together, our results show that, at low doses, the venom of B. leucurus induces transient, acute hypotension in anesthetized rats following systemic vasodilation in a dose-dependent way. In addition, we provide clear evidence of the involvement of the enzymatic activity of blD-PLA₂ in this cardiovascular response, acting via the production of vasodilating prostanoids.

Sexual and ontogenetic variation of Bothrops leucurus venom

Various factors, such as geographical origin, climate, sex, age and diet can influence the composition and pathophysiological activities of snake venoms. In this study, we examined the sexual and ontogenetic variations in the venom of Bothrops leucurus, a pitviper responsible for more than 80% of the snakebites in the state of Bahia, northeastern Brazilian. The venoms of 31 snakes were pooled according to sex and age (young, adult and old) and screened by SDS-PAGE (in reducing and non-reducing conditions), reverse-phase high performance liquid chromatography (RP-HPLC), gelatin zymography, and immunoblotting with therapeutic bothropic antivenom (BAV) from the Instituto Butantan. The electrophoretic and chromatographic profiles showed intraspecific ontogenetic variation, whereas sexual variations were less evident. All venoms showed gelatinolytic activity associated with 50-75 kDa protein bands. In addition, all venoms, regardless of the snakes' sex and age, cross-reacted to similar extents with BAV. Our findings show that B. leucurus venom changes during ontogenetic development and demonstrate sexual differences in its composition, indicating differences in biological activity.

Fibrinogen-clotting enzyme, pictobin, from Bothrops pictus snake venom. Structural and functional characterization

A thrombin-like enzyme, pictobin, was purified from Bothrops pictus snake venom. It is a 41-kDa monomeric glycoprotein as showed by mass spectrometry and contains approx. 45% carbohydrate by mass which could be removed with N-glycosidase. Pictobin coagulates plasma and fibrinogen, releasing fibrinopeptide A and induces the formation of a friable/porous fibrin network as visualized by SEM. The enzyme promoted platelet aggregation in human PRP and defibrination in mouse model and showed catalytic activity on chromogenic substrates S-2266, S-2366, S-2160 and S-2238. Pictobin interacts with the plasma inhibitor α2-macroglobulin, which blocks its interaction with fibrinogen but not with the small substrate BApNA. Heparin does not affect its enzymatic activity. Pictobin cross reacted with polyvalent bothropic antivenom, and its deglycosylated form reduced its catalytic action and antivenom reaction. In breast and lung cancer cells, pictobin inhibits the fibronectin-stimulated migration. Moreover, it produces strong NADH oxidation, mitochondrial depolarization, ATP decrease and fragmentation of mitochondrial network. These results suggest by first time that a snake venom serinprotease produces mitochondrial dysfunction by affecting mitochondrial dynamics and bioenergetics. Structural model of pictobin reveals a conserved chymotrypsin fold β/β hydrolase. These data indicate that pictobin has therapeutic potential in the treatment of cardiovascular disorders and metastatic disease.

Structural feature and self-assembly properties of type II collagens from the cartilages of skate and sturgeon

Acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) were extracted and purified from the cartilages of skate and sturgeon. Their typical structure and physicochemical properties were evaluated by circular dichroism (CD), X-ray diffraction (XRD), and so on. Results showed that the extracted collagen was likely identified as collagen-II composed of three α-chains (135 kDa), with the typical peptide sequence of Gly-X-Y. It showed the collagen retained the native and intact triple helical structure, and its intensity ratio of the positive and negative absorption peaks (Rpn) was 0.19-0.25. In addition, the extracted collagen exhibited obvious self-assembly behavior with the concentration above 0.3 mg/mL, the adjustment of pH 7.4-7.6 and the NaCl concentration of 120 mmol/L. The critical aggregate mass concentrations of pepsin-soluble collagens from skate and sturgeon were 0.93 and 0.86 g/L, respectively. Therefore, collagens from skate and sturgeon cartilages have potential commercial application.

Isolation and Characterization of Poecistasin, an Anti-Thrombotic Antistasin-Type Serine Protease Inhibitor from Leech Poecilobdella manillensis

Antistasin, first identified as a potent inhibitor of the blood coagulation factor Xa, is a novel family of serine protease inhibitors. In this study, we purified a novel antistasin-type inhibitor from leech Poecilobdella manillensis called poecistasin. Amino acid sequencing of this 48-amino-acid protein revealed that poecistasin was an antistasin-type inhibitor known to consist of only one domain. Poecistasin inhibited factor XIIa, kallikrein, trypsin, and elastase, but had no inhibitory effect on factor Xa and thrombin. Poecistasin showed anticoagulant activities. It prolonged the activated partial thromboplastin time and inhibited FeCl₃-induced carotid artery thrombus formation, implying its potent function in helping Poecilobdella manillensis to take a blood meal from the host by inhibiting coagulation. Poecistasin also suppressed ischemic stroke symptoms in transient middle cerebral artery occlusion mice model. Our results suggest that poecistasin from the leech Poecilobdella manillensis plays a crucial role in blood-sucking and may be an excellent candidate for the development of clinical anti-thrombosis and anti-ischemic stroke medicines.

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.

Mechanistic insights into functional characteristics of native crotamine

The chemical composition of snake venoms is a complex mixture of proteins and peptides that can be pharmacologically active. Crotamine, a cell-penetrating peptide, has been described to have antimicrobial properties and it exerts its effects by interacting selectively with different structures, inducing changes in the ion flow pattern and cellular responses. However, its real therapeutic potential is not yet fully known. Bearing in mind that crotamine is a promising molecule in therapeutics, this study investigated the action of purified molecule in three aspects: I) antibacterial action on different species of clinical interest, II) the effect of two different concentrations of the molecule on platelet aggregation, and III) its effects on isolated mitochondria. Crotamine was purified to homogeneity in a single step procedure using Heparin Sepharose. The molecular mass of the purified enzyme was 4881.4 Da, as determined by mass spectrometry. To assess antibacterial action, changes in the parameters of bacterial oxidative stress were determined. The peptide showed antibacterial activity on Escherichia coli (MIC: 2.0 μg/μL), Staphylococcus aureus (MIC: 8-16 μg/μL) and methicillin-resistant Staphylococcus aureus (MIC: 4.0-8.0 μg/μL), inducing bacterial death by lipid peroxidation and oxidation of target proteins, determined by thiobarbituric acid reactive substances and sulfhydryl groups, respectively. Crotamine induced increased platelet aggregation (IPA) at the two concentrations analyzed (0.1 and 1.4 μg/μL) compared to ADP-induced aggregation of PRP. Mitochondrial respiratory parameters and organelle structure assays were used to elucidate the action of the compound in this organelle. The exposure of mitochondria to crotamine caused a decrease in oxidative phosphorylation and changes in mitochondrial permeability, without causing damage in the mitochondrial redox state. Together, these results support the hypothesis that, besides the antimicrobial potential, crotamine acts on different molecular targets, inducing platelet aggregation and mitochondrial dysfunction.

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.

Rapid purification of a new P-I class metalloproteinase from Bothrops moojeni venom with antiplatelet activity

The present study aimed to evaluate the proteolytic and biological activities of a new metalloproteinase from B. moojeni venom. The purification of BmooMPα-II was carried out through two chromatographic steps (ion-exchange and affinity). BmooMPα-II is a monomeric protein with an apparent molecular mass of 22.5 kDa on SDS-PAGE 14% under nonreducing conditions. The N-terminal sequence (FSPRYIELVVVADHGMFTKYKSNLN) revealed homology with other snake venom metalloproteinases, mainly among P-I class. BmooMPα-II cleaves Aα-chain of fibrinogen followed by Bβ-chain, and does not show any effect on the γ-chain. Its optimum temperature and pH for the fibrinogenolytic activity were 30–50°C and pH 8, respectively. The inhibitory effects of EDTA and 1,10-phenantroline on the fibrinogenolytic activity suggest that BmooMPα-II is a metalloproteinase. This proteinase was devoid of haemorrhagic, coagulant, or anticoagulant activities. BmooMPα-II caused morphological alterations in liver, lung, kidney, and muscle of Swiss mice. The enzymatically active protein yet inhibited collagen, ADP, and ristocetin-induced platelet aggregation in a concentration-dependent manner. Our results suggest that BmooMPα-II contributes to the toxic effect of the envenomation and that more investigations to elucidate the mechanisms of inhibition of platelet aggregation may contribute to the studies of snake venom on thrombotic disorders.

Isolation and biochemical characterization of a new thrombin-like serine protease from Bothrops pirajai snake venom

This paper presents a novel serine protease (SP) isolated from Bothrops pirajai, a venomous snake found solely in Brazil that belongs to the Viperidae family. The identified SP, named BpirSP-39, was isolated by three chromatographic steps (size exclusion, bioaffinity, and reverse phase chromatographies). The molecular mass of BpirSP-39 was estimated by SDS-PAGE and confirmed by mass spectrometry (39,408.32 Da). The protein was able to form fibrin networks, which was not observed in the presence of serine protease inhibitors, such as phenylmethylsulfonyl fluoride (PMSF). Furthermore, BpirSP-39 presented considerable thermal stability and was apparently able to activate factor XIII of the blood coagulation cascade, unlike most serine proteases. BpirSP-39 was capable of hydrolyzing different chromogenic substrates tested (S-2222, S-2302, and S-2238) while Cu(2+) significantly diminished BspirSP-39 activity on the three tested substrates. The enzyme promoted platelet aggregation and also exhibited fibrinogenolytic, fibrinolytic, gelatinolytic, and amidolytic activities. The multiple alignment showed high sequence similarity to other thrombin-like enzymes from snake venoms. These results allow us to conclude that a new SP was isolated from Bothrops pirajai snake venom.

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).

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.

Bmoo FIBMP-I: A New Fibrinogenolytic Metalloproteinase from Bothrops moojeni Snake Venom

A new fibrinogenolytic metalloproteinase (Bmoo FIBMP-I) was purified from Bothrops moojeni snake venom. This enzyme was isolated through a combination of three chromatographic steps (ion-exchange, molecular exclusion, and affinity chromatography). Analyses by reverse phase chromatography, followed by mass spectrometry, showed the presence of enzyme isoforms with average molecular mass of 22.8 kDa. The SDS-PAGE analyses showed a single chain of 27.6 kDa, in the presence and absence of reducing agent. The protein has a blocked N-terminal. One of the peptides obtained by enzymatic digestion of a reduced and S-alkylated isoform was completely sequenced by mass spectrometry (MS/MS). Bmoo FIBMP-I showed similarity with hemorrhagic factor and several metalloproteinases (MP). This enzyme degraded Aα-chain faster than the Bβ-chain and did not affect the γ-chain of bovine fibrinogen. The absence of proteolytic activity after treatment with EDTA, together with the observed molecular mass, led us to suggest that Bmoo FIBMP-I is a member of the P-I class of the snake venom MP family. Bmoo FIBMP-I showed pH-dependent proteolytic activity on azocasein, but was devoid of coagulant, defibrinating, or hemorrhagic activities. The kinetic parameters of proteolytic activity in azocasein were determined (V max = 0.4596 Uh(-1)nmol(-1) ± 0.1031 and K m = 14.59 mg/mL ± 4.610).

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 functional characterization of proinflammatory acidic phospholipase A2 from Bothrops leucurus snake venom

In the present study, an acidic PLA(2), designated Bl-PLA(2), was isolated from Bothrops leucurus snake venom through two chromatographic steps: ion-exchange on CM-Sepharose and hydrophobic chromatography on Phenyl-Sepharose. Bl-PLA(2) was homogeneous on SDS-PAGE and when submitted to 2D electrophoresis the molecular mass was 15,000Da and pI was 5.4. Its N-terminal sequence revealed a high homology with other Asp49 acidic PLA(2)s from snake venoms. Its specific activity was 159.9U/mg and the indirect hemolytic activity was also higher than that of the crude venom. Bl-PLA(2) induced low myotoxic and edema activities as compared to those of the crude venom. Moreover, the enzyme was able to induce increments in IL-12p40, TNF-α, IL-1β and IL-6 levels and no variation of IL-8 and IL-10 in human PBMC stimulated in vitro, suggesting that Bl-PLA(2) induces proinflammatory cytokine production by human mononuclear cells. Bothrops leucurus venom is still not extensively explored and knowledge of its components will contribute for a better understanding of its action mechanism.

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.

Structural and functional comparison of proteolytic enzymes from plant latex and snake venoms

This work describes classification, functions, location, inhibition, activation, and therapeutic applications of proteases from snake venoms and vegetables. Snake venoms and vegetables can present toxins that unchain necrosis or proteolysis due to the direct cytotoxic action of venom proteases. These proteases are potential tools in the development of drugs for the prevention and treatment of several illnesses. We report herein mainly fibrinogenolytic metallo proteases and serine proteases ("thrombin-like"). These enzymes are extensively used in the treatment and prevention of thrombotic disorders, since they serve as defibrinogenating agents. The therapeutic uses of fibrin(ogen)olytic metallo proteases hold promise for clinical application due to potential in reversing the effects of thrombosis; this has been shown to be an alternative approach to the prevention and treatment of cardiovascular disorders, which are among the most prominent causes of mortality around the world. Plant proteases can be utilized for many cellular and molecular activities, in antibacterial and anticancer therapies, and in the treatment of snakebites, inhibiting snake venom activities such as blood-clotting, defibrinogenation, and fibrin(ogen)olytic and hemorrhagic actions. These toxins also display potential for clinical use in the treatment of hemostatic disorders.

Purification and biochemical characterization of Eumiliin from Euphorbia milii var. hislopii latex

A protease, which we designate Eumiliin, was isolated from the latex of Euphorbia milii var. hislopii by a combination of ion-exchange chromatographic steps using DEAE-Sephacel and gel-filtration with Sephadex G-75. Eumiliin is a monomeric protein with an apparent molecular mass of 30 kDa by SDS-PAGE under reducing conditions and gave one main peak at 29,814 KDa in MALDI-TOF/TOF mass spectrometry. Eumiliin has caseinolytic and fibrinogenolytic activities, but no hemorrhagic or defibrinating activities. The enzyme readily hydrolyzes the Aalpha-chain of fibrinogen and, more slowly, the Bbeta-chain. Its fibrinogenolytic activity is inhibited by beta-mercaptoethanol and leupeptin. In contrast, EDTA and benzamidine did not affect the activity of Eumiliin. The caseinolytic activity of Eumiliin had a pH optimum of 8.0 and was stable in solution at up to 40 degrees C; activity was completely lost at >or=80 degrees C. Intraplantar injection of Eumiliin (1-25 microg/paw) caused a dose- and time-dependent hyperalgesia, which peaked 1-5h after enzyme injection. Intraplantar injection of Eumiliin (1-25 microg/paw) also caused an oedematogenic response that was maximal after 1h. Morphological analyses indicated that Eumiliin induced an intense myonecrosis, with visible leukocyte infiltrate and damaged muscle cells 24h after injection.

Bhalternin: Functional and structural characterization of a new thrombin-like enzyme from Bothrops alternatus snake venom

A serine protease from Bothrops alternatus snake venom was isolated using DEAE-Sephacel, Sephadex G-75 and Benzamidine-Sepharose column chromatography. The purified enzyme, named Bhalternin, ran as a single protein band on analytical polyacrylamide gel electrophoresis (SDS-PAGE) and showed molecular weights of 31,500 and 27,000 under reducing and non-reducing conditions, respectively. Its complete cDNA was obtained by RT-PCR and the 708bp codified for a mature protein of 236 amino acid residues. The multiple alignment of its deduced amino acid sequence showed a structural similarly with other serine proteases from snake venoms. Bhalternin was proteolytically active against bovine fibrinogen and albumin as substrates. When Bhalternin and bovine fibrinogen were incubated at 37 degrees C, at a ratio of 1:100 (w/w), the enzyme cleaved preferentially the Aalpha-chain, apparently not degrading the Bbeta and gamma-chains. Stability tests showed that the intervals of optimum temperature and pH for the fibrinogenolytic activity were 30-40 degrees C and 7.0-8.0, respectively. Also, the inhibitory effects of benzamidine on the fibrinogenolytic activity of Bhalternin indicate that it is a serine protease. This enzyme caused morphological alterations in heart, liver, lung and muscle of mice and it was found to cause blood clotting in vitro and defibrinogenation when intraperitoneally administered to mice, suggesting it to be a thrombin-like enzyme. Therefore, Bhaltenin may be of interest as a therapeutic agent in the treatment and prevention of thrombotic disorders.

Isolation and characterization of the thrombin-like enzyme from Cryptelytrops purpureomaculatus venom

A thrombin-like enzyme, purpurase, was purified from the Cryptelytrops purpureomaculatus (mangrove pit viper) venom using high performance ion-exchange and gel filtration chromatography. The purified sample (termed purpurase) yielded a homogeneous band in SDS-polyacrylamide gel electrophoresis with a molecular weight of 35,000. The N-terminal sequence of purpurase was determined to be VVGGDECNINDHRSLVRIF and is homologous to many other venom thrombin-like enzymes. Purpurase exhibits both arginine ester hydrolase and amidase activities. Kinetic studies using tripeptide chromogenic anilide substrates showed that purpurase is not fastidious towards its substrate. The clotting times of fibrinogen by purpurase were concentration dependent, with optimum clotting activity at 3mg fibronogen/mL. The clotting activity by purpurase was in the following decreasing order: cat fibrinogen>human fibrinogen>dog fibrinogen>goat fibrinogen>>rabbit fibrinogen. Reversed-phase HPLC analysis of the products of action of purpurase on bovine fibrinogen showed that only fibrinopeptide A was released. Indirect ELISA studies showed that anti-purpurase cross-reacted strongly with venoms of most crotalid venoms, indicating the snake venom thrombin-like enzymes generally possess similar epitopes. In the more specific double-sandwich ELISA, however, anti-purpurase cross-reacted only with venoms of certain species of the Trimeresurus complex, and the results support the recent proposed taxonomy changes concerning the Trimeresurus complex.

Isolation and characterization of a new serine protease with thrombin-like activity (TLBm) from the venom of the snake Bothrops marajoensis

The thrombin-like serine protease TLBm from Bothrops marajoensis was isolated in one chromatographic step in reverse phase HPLC. Its molecular mass was 33239.95 Da, as based on the determined primary structure and confirmed experimentally by MALDI-TOF mass spectrometry (33332.5 Da) and it contains 12 half-cysteine residues. This TLBm exhibited high specificity for BArhoNA, Michaelis-Menten behavior with K(m) 2.3x10(-1)M and the V(max) 0.52x10(-1) nmoles rho-NA/lt/min for this substrate. TLBm also showed ability to coagulate bovine fibrinogen and was inhibited by soybean trypsin inhibitor, EDTA and S(Dm) from the serum of the species Didelphis marsupialis. The primary structure of TLBm showed the presence of His(45), Asp(103) and Ser(228) residues in the corresponding positions of the catalytic triad established in the serine proteases and Ser(228) are inhibited by phenylmethylsulfonyl fluoride (PMSF). Amino acid analysis showed a high content of Asp, Glu, Gly, Ser, Ala and Pro as well as 12 half-cysteine residues and calculated pI of 6.47; TLBm presented 285 amino acid residues. In this work, we investigated the ability of TLBm to degrade fibrinogen and we observed that it is able to cause alpha- and beta-chain cleavage. Enzymatic as well as the platelet aggregation activities were strongly inhibited when incubated with PMSF, a specific inhibitor of serine protease. Also, TLBm induced platelet aggregation in washed and platelet-rich plasma, and in both cases, PMSF inhibited its activity.

The structure of CMS2MS2, a mitogenic protein isolated from Carica candamarcensis

In a recent study we showed that two proteinases (CMS2MS2 and CMS2MS3) from Carica candamarcensis enhance mammalian cell proliferation. The aim of the present study is the determination of the primary structure of CMS2MS2 and prediction of its three-dimensional structure. The protein contains 214 residues, including the catalytic triad composed of Cys(25), His(159), and Asn(175). A phylogenetic tree analysis demonstrated that CMS2MS2 ranks closer to chymopapain than to papain. The overall predicted three-dimensional structure is similar to proteinases from the papain family. These results suggest that minor structural differences within CMS2MS2 must account for its proliferative action.

Affinity purification of serine proteinase from Deinagkistrodon acutus venom

An affinity protocol was developed for the preparation of the main serine proteinase from Deinagkistrodon acutus venom on industrial scales. As affinity ligand, l-arginine was composed to medium and its structure was confirmed by ESI-MS analysis. The purification process consisted of one major affinity chromatography step to remove more than 95% of other proteins, and a polishing step of DEAE ion-exchange chromatography for removal of minor contaminants. The serine proteinase was 100% pure analyzed on HPLC Vydac C4 column, 99.4% on TSK G3000SW column, and 97.7% with SDS-PAGE analysis. The yield of the main serine proteinase was 3.6% of crude venom protein, the recoveries of typical fibrinogen (Fg) clotting activity and arginine esterase activity of serine proteinase were 82.2% and 84%, higher than those of other reported traditional protocols, the proteinase also showed arginine amidase activity. Reducing SDS-PAGE analysis showed that the arginine esterase was a single polypeptide with the mass of approximately 40 kDa, while MALDI-TOF-TOF-MS analysis showed that the purified proteinase should be a approximately 34 kDa glycoprotein. The desorption constant Kd and the theoretical maximum absorption Qmax on the affinity medium were 9.93 x 10(-5) and 38.1mg/g medium in absorption analysis.

Structural and functional characterization of a P-III metalloproteinase, leucurolysin-B, from Bothrops leucurus venom

Leucurolysin-B (leuc-B) is an hemorrhagic metalloproteinase found in the venom of Bothrops leucurus (white-tailed-jararaca) snake. By means of liquid chromatography consisting of gel filtration on Sephracryl S-200, S-300 and ion-exchange on DEAE Sepharose, leuc-B was purified to homogeneity. The proteinase has an apparent molecular mass of 55kDa as revealed by the reduced SDS-PAGE, and represents approximately 1.2% of the total protein in B. leucurus venom. The partial amino acid sequence of leuc-B was determined by automated Edman sequencing of peptides derived from digests of the S-reduced and alkylated protein with trypsin. Leuc-B exhibits the characteristic motif of metalloproteinases, HEXXHXXGXXH and a methionine-containing turn of similar conformation ("Met-turn"), which forms a hydrophobic basis for the zinc ions and the three histidine residues involved as ligands. Leuc-B has been characterized as a P-III metalloproteinase and possesses a multidomain structure including a metalloproteinase, a disintegrin-like (ECD sequence instead of the typical RGD motif) and a cysteine-rich C-terminal domain. Leuc-B contains three potential sites of N-glycosylation. The enzyme only cleaves the Ala14-Leu15 peptide bond of the oxidized insulin B-chain and preferentially hydrolyzes the Aalpha-chain of fibrinogen and the alpha-chain of fibrin. Its proteolytic activity was completely inhibited by metal chelating agents but not by other typical proteinase inhibitors. In addition, its enzymatic activity was stimulated by the divalent cations Ca2+ and Mg2+ but inhibited by Zn2+ and Cu2+. The catalytic activity of leuc-B on extracellular matrix proteins could readily lead to loss of capillary integrity resulting in hemorrhage occurring at those sites (MHD=30ng in rabbit), with alterations in platelet function. In summary, here we report the isolation and the structure-function relationship of a P-III snake venom metalloproteinase.

Cytotoxic, thrombolytic and edematogenic activities of leucurolysin-a, a metalloproteinase from Bothrops leucurus snake venom

Leucurolysin-a (leuc-a), a 23 kDa non-hemorrhagic metalloproteinase, is found in venom of the viper Bothrops leucurus. Here, we examine the biological consequences of leuc-a, including thrombolytic activity, direct effects on endothelial cells in culture and edematogenic activity in vivo. We demonstrate fibrinolytic activity of leuc-a, in which the protease specifically degrades alpha, beta, and gamma-gamma chains. While not causing hemorrhaging, leuc-a does cause thrombolytic activities in whole blood clots. Endothelial cells are highly resistant to leuc-a in culture. Cell viability suffered only when cells were exposed to large quantities of the protease. Nevertheless, leuc-a induces changes in cell morphology. The impact of leuc-a on cell adhesion was confirmed by an adhesion assay, in which cell adhesion to fibronectin decreased due to leuc-a. This mild cellular impact is unlike that of crude venom, where lower concentrations triggered cell death and a greater reduction in cell adhesion. Also, leuc-a increased microvessel permeability with marked edema in mice peritoneum and foot pads. These effects are similar to those of other P-I class SVPMs. These in vivo effects were weaker when crude venom was tested. In conclusion, albeit not showing significant hemorrhagic activity, leuc-a can induce a prominent edema which appears to be significant in the local effects observed after B. leucurus venom accidents.

The cost of Latin American science Introduction for the second issue of CBP-Latin America

Latin American researchers in science and engineering (S&E), including those in biology and biomedical sciences, are frequently exposed to unstable conditions of financial support, material and human resources, and a limited number of positions at public and private institutions. Such uncertainties impose continuous challenges for the scientific community which, in the best of cases, responds with careful planning and creativity, and in the worst scenario endures the migration of scientists to the USA or Europe. Still, the number of scientific publications from Latin American institutions in the last decade increased at a much faster rate than publications from the USA and Canada. A brief analysis per country of the gross domestic product (GDP) spent in research and development (R&D) and the S&E production reported by the Pascal bibliographic database suggests that the number and quality of S&E publications is directly proportional to the financial support for R&D. However, the investment in R&D in Latin America did not increase at the same rate (from 0.49 to 0.55% of GDP, from 1990 to 2003) at which S&E publications did in the same period (2.9-fold increase, from 1988 to 2001). In Latin America, the traditional financial support for scientific research continues to be from federal and state government funds, associated in some cases with institutional funds that are mostly directed towards administrative costs and infrastructure maintenance. The aim of this introduction is to briefly discuss the production cost of articles published in refereed S&E journals, including the cost of the scientific research behind them, and, at the same time, to increase the awareness of the high quality of scientific research in Latin American institutions despite the many challenges, especially financial constraints, faced by their scientists. The second issue of Comparative Biochemistry and Physiology dedicated to Latin America ("The Face of Latin American Comparative Biochemistry and Physiology") celebrates, by means of 26 manuscripts from five countries, the diversity and quality of biological science in the continent.