**2. Biotechnological and pharmacological applications of snake venom toxins**

While the initial interest in snake venom research was to understand how to combat effects of snakebites in humans and to elucidate toxins mechanisms, snake venoms have become a fertile area for the discovery of novel products with biotechnological and/or pharmacologi‐ cal applications [13-14]. Since then, many different products have been developed based on purified toxins from snake venoms, as well recent studies have been showing new potential molecules for a variety of applications [15].

#### **2.1. Toxins acting on cardiovascular system**

Increase in blood pressure is often a transient physiological response to stressful stimuli, which allows the body to react to dangers or to promptly increase activity. However, when the blood pressure is maintained at high levels for an extended period, its long term effects are highly undesirable. Persistently high blood pressure could cause or accelerate multiple pathological conditions such as organ (heart and kidney) failure and thrombosis events (heart attack and stroke) [14]. So, it is important to lower the blood pressure of high-rick pa‐ tients through use of specific anti-hypertensive agents, and in this scenario, snake venom toxins has been shown to be promising sources [14-15]. This is because it has long been not‐ ed that some snake venoms drastically lower the blood pressure in human victims and ex‐ perimental animals [15]. The first successful example of developing a drug from an isolated toxin was the anti-hypertensive agent Capoten® (captopril), an angiotensin-converting en‐ zyme (ACE) inhibitor modeled from a venom peptide isolated from *Bothrops jararaca* venom [16]. These bradykinin-potentiating peptides (BPPs) are venom components which inhibits the breakdown of the endogenous vasodilator bradykinin while also inhibiting the synthesis of the endogenous vasoconstrictor angiotensin II, leading to a reduction in blood pressure [15]. BPPs have also been identified in *Crotalus durissus terrificus* venom [17]. Snake venom represents one of the major sources of exogenous natriuretic peptides (NPs) [18]. The first venom NP was identified from *Dendroaspis angusticeps* snake venom and was named *Den‐ droaspis* natriuretic peptide (DNP) [19]. Other venom NPs were also reported in various snake species, such as *Micrurus corallinus* [20], *B. jararaca* [4], *Trimeresurus flavoviridis*, *Trimer‐ esurus gramineus*, *Agkistrodon halys blomhoffii* [21], *Pseudocerastes persicus* [22], *Crotalus durissus cascavella* [23], *Bungarus flaviceps* [24], among others. L-type Ca2+-channels blockers identified in snake venoms include calciseptine [25] and FS2 toxins [26] from *Dendroaspis polylepis poly‐ lepis*, C10S2C2 from *D. angusticeps* [27], S4C8 from *Dendroaspis jamesoni kaimosae* [28] and stej‐ nihagin, a metalloproteinase from *Trimeresurus stejnegeri* [29].

### **2.2. Toxins acting on hemostasis**

and binding site on different channels or channel subtypes. The venom is constituted by mucopolysaccharides, hyaluronidases, phospholipases, serotonins, histamines, enzyme in‐ hibitors, antimicrobials and proteins namely neurotoxic peptides. Scorpion peptides presents specificity and high affinity and have been used as pharmacological tools to charac‐ terize various receptor proteins involved in normal ion channel functionating, as abnormal channel functionating in cases of diseases. The venoms can be characterized by identifica‐ tion of peptide toxins analysis of the structure of the toxins and also have proven to be among the most and selective antagonists available for voltage-gated channels permeable to

An Integrated View of the Molecular Recognition and Toxinology - From Analytical Procedures to Biomedical

, and Ca2+. The neurotoxic peptides and small proteins lead to dysfunction and pro‐

voke pathophysiological actions, such as membrane destabilization, blocking of the central, and peripheral nervous systems or alteration of smooth or skeletal muscle activity [5-8]. Spi‐ der venoms are complex mixtures of biologically active compounds of different chemical na‐ ture, from salts to peptides and proteins. Specificity of action of some spider toxins is unique along with high toxicity for insects, they can be absolutely harmless for members of other taxons, and this could be essential for investigation of insecticides. Several spider toxins have been identified and characterized biochemically. These include mainly ribonucleotide phosphohydrolase, hyaluronidases, serine proteases, metalloproteases, insecticidal peptides and phospholipases D [9-10]. Venoms from toads and frogs have been extensively isolated and characterized showing molecules endowed with antimicrobial and/or cytotoxic activi‐ ties [11]. Studies involving the molecular repertoire of the venom of bees and wasps have revealed the partial isolation, characterization and biological activity assays of histamines, dopamines, kinins, phospholipases and hyaluronidases. The venom of caterpillars has been partially characterized and contains mainly ester hydrolases, phospholipases and proteases [12]. The purpose of this chapter is to present the main toxins isolated and characterized from the venom of venomous animals, focusing on their biotechnological and pharmacolog‐

**2. Biotechnological and pharmacological applications of snake venom**

While the initial interest in snake venom research was to understand how to combat effects of snakebites in humans and to elucidate toxins mechanisms, snake venoms have become a fertile area for the discovery of novel products with biotechnological and/or pharmacologi‐ cal applications [13-14]. Since then, many different products have been developed based on purified toxins from snake venoms, as well recent studies have been showing new potential

Increase in blood pressure is often a transient physiological response to stressful stimuli, which allows the body to react to dangers or to promptly increase activity. However, when the blood pressure is maintained at high levels for an extended period, its long term effects

K+ , Na+

Applications

24

ical applications.

molecules for a variety of applications [15].

**2.1. Toxins acting on cardiovascular system**

**toxins**

Desintegrins are a family of cysteine-rich low molecular weight proteins that inhibits vari‐ ous integrins and that usually contain the integrin-binding RGD motif, that binds the GPIIa/ IIIb receptor in platelets, thus prevents the binding of fibrinogen to the receptor and conse‐ quently platelet aggregation [13]. Two drugs, tirofiban (Aggrastat®) and eptifibatide (Integ‐ rillin®) were designed based on snake venom disintegrins and are avaliable in the market as antiplatelet agents, approved for preventing and treating thrombotic complications in pa‐ tients undergoing percutaneous coronay intervention and in patients with acute cornonary sydrome [30-31]. Tirofiban has a non-peptide structure mimicking the RDG motif of the dis‐ integrin echistatin from *Echis carinatus* [30]. Eptifibatide is a cyclic peptide based on the KGD motif of barbourin from *Sisturus miliaris barbouri* snake [31]. Recently, leucurogin, a new re‐ combinant disintegrin was cloned from *Bothrops leucurus*, being a potent agent upon platelet aggregation [32]. Thrombin-like enzymes (TLEs) are proteases reported from many different crotalid, viperid and colubrid snakes that share some functional similarity with thrombin [13]. TLEs are not inactivated by heparin-antithrombin III complex (the physiological inhibi‐ tor of thrombin), and, differently to thrombin, they are not able to activate FXIII (the enzyme that covalently cross-links fibrin monomer to form insoluble clots). These are interesting properties, because although being procoagulants *in vitro*, TLEs have the clinical results of being anti-coagulants, by the depletion of plasma level of fibrinogen, and the clots formed are easily soluble and removed from the body. At same time, thrombolysis is enhanced by

stimulation of endogenous plasminogen activators binding to the noncrosslinked fibrin [13]. Batroxobin (Defibrase®) was isolated and purified from *Bothrops atrox* venom [33] and an‐ crod (Viprinex®) from *Agkistrodon rhodostoma* [34]. Haemocoagulase® is a mixture of two pro‐ teinases isolated from *B. atrox* venom, acting on blood coagulation by two mechanisms: the first having a thrombin-like activity and the second having a thromboplastin-like activity, activating FX which in turn converts prothrombin into thrombin. It is indicated for the pre‐ vention and treatment of hemorrhages of a variety of origins [13]. Other toxins acting on he‐ mostasis with potential biotechnological/pharmacological applications has been purified and characterized from several snake venoms, such as bhalternin from *Bothrops alternatus* [35], bleucMP from *B. leucurus* [36], VLH2 from *Vipera lebetina* [37], trimarin from *Trimeresu‐ rus malabaricus* [38], BE-I-PLA2 from *Bothrops erythromelas* [39], among others.

such as arachidonic acid derived eicosanoids, various lysophospholipids and platelet acti‐ vating factors through cyclooxygenase and lipoxygenase pathways [57]. In a recent study, was described the first complete nucleotide sequence of a βPLI from venom glands of *Lache‐ sis muta* by a transcriptomic analysis [58]. Recently, was purified from the venom of *Crotalus durissus terrificus* a hyaluronidase (named Hyal) that was able to provide a highly antiede‐ matogenic acitivity [59]. Crotapotin, a subunit of crotoxin, from *C. d. terrificus*, has been re‐ ported to possess immunossupressive activity, associated to an increase in the production of prostaglandin E2 by macrophages, consequently reducing the proliferative response of lym‐ phocytes [60]. Various elapid and viperid venoms have been reported to induce antinocicep‐ tion through their neurotoxins and myotoxins [61]. *C. d. terrificus* venom induces neurological symptoms in their victims, but, contrary to most venoms from other species, it does not induce pain or severe tissue destruction at the site of inoculation, being usual the sensation of paresthesia in the affected area [62]. Based on this, several studies have been carried out with this venom, being reported in the literature several molecules with antinoci‐ ceptive activity from *C. d. terrificus* venom, such as crotamine [63] and crotoxin [64]. Has been demonstrated that the anti-nociceptive effect of crotamine involve both central and pe‐ ripheral mechanisms, being 30-fold higher than the produced by morphine [63]. Studies suggest that crotoxin has antinociceptive effect mediated by an action on the central nervous system, without involvement of muscarinic and opioid receptors [64]. Other antinociceptive peptides isolated from snake venoms are cobrotoxin, a neurotoxin isolated from *Naja atra*

Toxins from Venomous Animals: Gene Cloning, Protein Expression and Biotechnological Applications

http://dx.doi.org/10.5772/52380

27

[65] and hannalgesin, a neurotoxin isolated from *Ophiophagus hannah* [66].

Venom-derived peptides are being evaluated as immunosuppressants for the treatment of autoimmune diseases and the prevention of graft rejection [67]. Studies have shown that an‐ ti-crotalic serum possesses an antibody content usually inferior to the antibody content of other anti-venom serum suggesting that the crotalic venom is a poor immunogen or that it has components with immunosuppressor activity [68]. Indeed, the immunosuppressive ef‐ fect of venom and crotoxin (a toxin isolated from *Crotalus durissus terrificus*) was reported [68]. Crotapotin, an acidic and non-toxic subunit of crotoxin, administrated by intraperito‐ neal route, significantly reduces the severity of experimental autoimmune neuritis, an exper‐ imental model for Guillain-Barré syndrome, which indicate a novel path for neuronal protection in this autoimmune disease and other inflammatory demyelinating neuropathies [69]. Inappropriate activation of complement system occurs in a large number of inflamma‐ tory, ischaemic and other diseases. Cobra venom factor (CVF) is an unusual venom compo‐ nent which exists in the venoms of different snake species, such as *Naja* sp., *Ophiophagus* sp. and *Hemachatus* sp. that activate complement system [70]. Due its similarity with C3 comple‐ ment system component, after binding to mammalian fB in plasma and cleavage of fB by fD, produces a C3 convertase, that is more stable than the other C3 convertases, and resistant to the fluid phase regulators. The CVF-Bb convertase consumes all plasma C3 obliterating the functionality of complement system [70]. Recently, a CVF named OVF was purified from the crude venom of *Ophiophagus hannah* and cloned by cDNA transcriptomic analysis of the

**2.5. Toxins acting on immunological system**

snake venom glands [71].

### **2.3. Toxins with antibiotic activity**

Antibiotics are a heterogeneous group of molecules produced by several organisms, includ‐ ing bacteria and fungi, presenting an antimicrobial profile, inducing the death of the agent or inhibiting microbial growth [40]. L-amino acid oxidases (LAAOs) are enantioselective flavoen‐ zymes catalyzing the stereospecific oxidative deamination of a wide range of L-amino acids to form α-keto acids, ammonia and hydrogen peroxide (H2O2). Antimicrobial activities are reported to various LAAOs, such as TJ-LAO from *Trimeresurus jerdonii* [41], Balt-LAAO-I from *Bothrops alternatus* [42], TM-LAO *Trimeresurus mucrosquamatus* [43], BpirLAAO-I from *Bo‐ throps pirajai* [44], casca LAO from *Crotalus durissus cascavella* [45], a LAAO from *Naja naja oxiana* [46], BmarLAAO from *Bothrops marajoensis* [47], among others. Recently, studies revealed that *B. jararaca* venom induced programmed cell death in epimastigotes of *Trypanossoma cruzi*, being this anti-*T. cruzi* activity associated with fractions of venoms with LAAO activity [48]. Secret‐ ed phospholipases A2 (sPLA2s) constitute a diverse group of enzymes that are widespread in nature, being particularly abundant in snake venoms. In addition to their catalytic activity, hydrolyzing the sn-2 ester bond of glycerophospholipids, sPLA2s display a range of biologi‐ cal actions, which may be either dependent or independent of catalytic action [49]. Eight sPLA2 myotoxins purified from crotalid snake venoms, including both Lys49 and Asp49-type iso‐ forms, were all found to express bactericidal activity [50]. EcTx-I from *Echis carinatus* [51], PnPLA2 from *Porthidium nasutum* [52] and BFPA [53] from *Bungarus fasciatus* also presented antimicrobial activity. Vgf-1, a small peptide from *Naja atra* venom had *in vitro* activity against clinically isolated multidrug-resistant strains of *Mycobacterium tuberculosis* [54]. Neuwiedase, a metalloproteinase from *Bothrops neuwiedi* snake venom, showed considerable effects of *Toxoplasma gondii* infection inhibition *in vitro* [55]. Recently, a study revealed that whole venom, crotoxin and sPLA2s (PLA2-CB and PLA2-IC) isolated from *Crotalus durissus terrificus* venom showed antiviral activity against dengue and yellow fever viruses, which are two of the most important arboviruses in public health [56].

#### **2.4. Toxins acting on inflammatory and nociceptive responses**

Various snake venoms are rich in secretory phospholipases A2 (sPLA2), which are potent pro-inflammatory enzymes producing different families of inflammatory lipid mediators

such as arachidonic acid derived eicosanoids, various lysophospholipids and platelet acti‐ vating factors through cyclooxygenase and lipoxygenase pathways [57]. In a recent study, was described the first complete nucleotide sequence of a βPLI from venom glands of *Lache‐ sis muta* by a transcriptomic analysis [58]. Recently, was purified from the venom of *Crotalus durissus terrificus* a hyaluronidase (named Hyal) that was able to provide a highly antiede‐ matogenic acitivity [59]. Crotapotin, a subunit of crotoxin, from *C. d. terrificus*, has been re‐ ported to possess immunossupressive activity, associated to an increase in the production of prostaglandin E2 by macrophages, consequently reducing the proliferative response of lym‐ phocytes [60]. Various elapid and viperid venoms have been reported to induce antinocicep‐ tion through their neurotoxins and myotoxins [61]. *C. d. terrificus* venom induces neurological symptoms in their victims, but, contrary to most venoms from other species, it does not induce pain or severe tissue destruction at the site of inoculation, being usual the sensation of paresthesia in the affected area [62]. Based on this, several studies have been carried out with this venom, being reported in the literature several molecules with antinoci‐ ceptive activity from *C. d. terrificus* venom, such as crotamine [63] and crotoxin [64]. Has been demonstrated that the anti-nociceptive effect of crotamine involve both central and pe‐ ripheral mechanisms, being 30-fold higher than the produced by morphine [63]. Studies suggest that crotoxin has antinociceptive effect mediated by an action on the central nervous system, without involvement of muscarinic and opioid receptors [64]. Other antinociceptive peptides isolated from snake venoms are cobrotoxin, a neurotoxin isolated from *Naja atra* [65] and hannalgesin, a neurotoxin isolated from *Ophiophagus hannah* [66].

### **2.5. Toxins acting on immunological system**

stimulation of endogenous plasminogen activators binding to the noncrosslinked fibrin [13]. Batroxobin (Defibrase®) was isolated and purified from *Bothrops atrox* venom [33] and an‐ crod (Viprinex®) from *Agkistrodon rhodostoma* [34]. Haemocoagulase® is a mixture of two pro‐ teinases isolated from *B. atrox* venom, acting on blood coagulation by two mechanisms: the first having a thrombin-like activity and the second having a thromboplastin-like activity, activating FX which in turn converts prothrombin into thrombin. It is indicated for the pre‐ vention and treatment of hemorrhages of a variety of origins [13]. Other toxins acting on he‐ mostasis with potential biotechnological/pharmacological applications has been purified and characterized from several snake venoms, such as bhalternin from *Bothrops alternatus* [35], bleucMP from *B. leucurus* [36], VLH2 from *Vipera lebetina* [37], trimarin from *Trimeresu‐*

An Integrated View of the Molecular Recognition and Toxinology - From Analytical Procedures to Biomedical

Antibiotics are a heterogeneous group of molecules produced by several organisms, includ‐ ing bacteria and fungi, presenting an antimicrobial profile, inducing the death of the agent or inhibiting microbial growth [40]. L-amino acid oxidases (LAAOs) are enantioselective flavoen‐ zymes catalyzing the stereospecific oxidative deamination of a wide range of L-amino acids to form α-keto acids, ammonia and hydrogen peroxide (H2O2). Antimicrobial activities are reported to various LAAOs, such as TJ-LAO from *Trimeresurus jerdonii* [41], Balt-LAAO-I from *Bothrops alternatus* [42], TM-LAO *Trimeresurus mucrosquamatus* [43], BpirLAAO-I from *Bo‐ throps pirajai* [44], casca LAO from *Crotalus durissus cascavella* [45], a LAAO from *Naja naja oxiana* [46], BmarLAAO from *Bothrops marajoensis* [47], among others. Recently, studies revealed that *B. jararaca* venom induced programmed cell death in epimastigotes of *Trypanossoma cruzi*, being this anti-*T. cruzi* activity associated with fractions of venoms with LAAO activity [48]. Secret‐ ed phospholipases A2 (sPLA2s) constitute a diverse group of enzymes that are widespread in nature, being particularly abundant in snake venoms. In addition to their catalytic activity, hydrolyzing the sn-2 ester bond of glycerophospholipids, sPLA2s display a range of biologi‐ cal actions, which may be either dependent or independent of catalytic action [49]. Eight sPLA2 myotoxins purified from crotalid snake venoms, including both Lys49 and Asp49-type iso‐ forms, were all found to express bactericidal activity [50]. EcTx-I from *Echis carinatus* [51], PnPLA2 from *Porthidium nasutum* [52] and BFPA [53] from *Bungarus fasciatus* also presented antimicrobial activity. Vgf-1, a small peptide from *Naja atra* venom had *in vitro* activity against clinically isolated multidrug-resistant strains of *Mycobacterium tuberculosis* [54]. Neuwiedase, a metalloproteinase from *Bothrops neuwiedi* snake venom, showed considerable effects of *Toxoplasma gondii* infection inhibition *in vitro* [55]. Recently, a study revealed that whole venom, crotoxin and sPLA2s (PLA2-CB and PLA2-IC) isolated from *Crotalus durissus terrificus* venom showed antiviral activity against dengue and yellow fever viruses, which are two of the most

*rus malabaricus* [38], BE-I-PLA2 from *Bothrops erythromelas* [39], among others.

**2.3. Toxins with antibiotic activity**

Applications

26

important arboviruses in public health [56].

**2.4. Toxins acting on inflammatory and nociceptive responses**

Various snake venoms are rich in secretory phospholipases A2 (sPLA2), which are potent pro-inflammatory enzymes producing different families of inflammatory lipid mediators Venom-derived peptides are being evaluated as immunosuppressants for the treatment of autoimmune diseases and the prevention of graft rejection [67]. Studies have shown that an‐ ti-crotalic serum possesses an antibody content usually inferior to the antibody content of other anti-venom serum suggesting that the crotalic venom is a poor immunogen or that it has components with immunosuppressor activity [68]. Indeed, the immunosuppressive ef‐ fect of venom and crotoxin (a toxin isolated from *Crotalus durissus terrificus*) was reported [68]. Crotapotin, an acidic and non-toxic subunit of crotoxin, administrated by intraperito‐ neal route, significantly reduces the severity of experimental autoimmune neuritis, an exper‐ imental model for Guillain-Barré syndrome, which indicate a novel path for neuronal protection in this autoimmune disease and other inflammatory demyelinating neuropathies [69]. Inappropriate activation of complement system occurs in a large number of inflamma‐ tory, ischaemic and other diseases. Cobra venom factor (CVF) is an unusual venom compo‐ nent which exists in the venoms of different snake species, such as *Naja* sp., *Ophiophagus* sp. and *Hemachatus* sp. that activate complement system [70]. Due its similarity with C3 comple‐ ment system component, after binding to mammalian fB in plasma and cleavage of fB by fD, produces a C3 convertase, that is more stable than the other C3 convertases, and resistant to the fluid phase regulators. The CVF-Bb convertase consumes all plasma C3 obliterating the functionality of complement system [70]. Recently, a CVF named OVF was purified from the crude venom of *Ophiophagus hannah* and cloned by cDNA transcriptomic analysis of the snake venom glands [71].

> serotonin and histamine, protease inhibitors, histamine releasers and polypeptidyl com‐ pounds. Scorpion venoms are a particularly rich source of small, mainly neurotoxic proteins or peptides interacting specifically with various ionic channels in excitable membranes [94].

Toxins from Venomous Animals: Gene Cloning, Protein Expression and Biotechnological Applications

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29

The first peptide from scorpion endowed effects of bradykinin and on arterial blood pres‐ sure was isolated from the Brazilian scorpion *Tityus serrulatus* [95]. These peptides named *Tityus serrulatus* Hypotensins have molecular masses ranging approximately from 1190 to 2700 Da [96]. Other scorpion bradykinin-potentiating peptides (BPPs) were reported to be found in the venom of the scorpions *Buthus martensii* Karsch [97] and *Leiurus quinquestriatus* [98]. These molecules can display potential as new drugs and could be of interest for bio‐

In order to defend themselves against the hostile environment, scorpions have developed potent defensive mechanisms that are part of innate and adaptive immunity [99]. Cysteinefree antimicrobial peptides have been identified and characterized from the venom of six scorpion species [100]. Antimicrobial peptides isolated from scorpion venom are important in the discovery of novel antibiotic molecules [101]. The first antimicrobial peptide isolated from scorpions were of the defensin type from *Leiurus quinquestriatus hebraeus* [102]. Later cytolitic and/or antibacterial peptides were isolated from scorpions belonging to the Buthi‐ dae, Scorpionidae, Ischnuridae, and Iuridae superfamilies hemo-lymph and venom [103-108]. The discovery of these peptides in venoms from Eurasian scorpions, Africa and the Americas, confirmed their widespread occurrence and significant biological function. Scorpine, a peptide from *Pandinus imperator* with 75 amino acids, three disulfide bridges, and molecular mass of 8350 Da has anti-bacterial and anti-malaria effects [104]. A cationic amphipatic peptide consisting of 45 amino acids has been purified from the venom of the southern African scorpion, *Parabuthus schlechteri*. At higher concentrations it forms non-se‐ lective pores into membranes causing depolarization of the cells [109]. Opistoporin1 and 2 (OP 1 and 2) was isolated from the venom of *Opistophthalmus carinatus*. These are amphi‐ pathic, cationic peptides which differ only in one amino acid residue. OP1 and PP were ac‐ tive against Gram-negative bacteria and both had hemolytic activity and antifungal activity. These effects are related to membrane permeabilization [106]. A new antimicrobial peptide, hadrurin, was isolated from *Hadrurus aztecus*. It is a basic peptide composed of 41 aminoacid residues with a molecular mass of 4436 Da, and contains no cysteines. It is a unique peptide among all known antimicrobial peptides described, only partially similar to the Nterminal segment of gaegurin 4 and brevinin 2e, isolated from frog skin. It would certainly be a model molecule for studying new antibiotic activities and peptide-lipid interactions [110]. Pandinin 1 and 2 are antimicrobial peptides have been identified and characterized from venom of the African scorpion *Pandinus imperator* [101]. Recently six novel peptides, named bactridines, were isolated from *Tityus discrepans* scorpion venom by mass spectrome‐

permeability induced by bactridines were

**3.1. Toxins acting on cardiovascular system**

technological purposes.

**3.2. Toxins with antibiotic activity**

try. The antimicrobial effects on membrane Na+

#### **2.6. Toxins with anticancer and cytotoxic activities**

Anticancer therapy is an important area for the application of proteins and peptides from venomous animals. Integrins play multiple important roles in cancer pathology including tumor cell proliferation, angiogenesis, invasion and metastasis [72]. Inhibition of angiogene‐ sis is one of the heavily explored treatment options for cancer, and in this scenario snake venom disintegrins represent a library of molecules with different structure, potency and specificity [1]. RGD-containing disintegrins was identified in several snake venoms, inhibit‐ ing tumor angiogenesis and metastasis, such as accutin (from *Agkistrodon acutus*) [73], sal‐ mosin (from *Agkistrodon halys brevicaudus*) [74], contortrostatin (from *Agkistrodon contortrix*) [75], jerdonin (from *Trimeresurus jerdonii*) [76], crotatroxin (from *Crotalus atrox*) [77], rhodos‐ tomin (from *Calloselasma rhodostoma*) [78] and a novel desintegrin from *Naja naja* [79]. The cytostatic effect of L-amino acid oxidases (LAAOs) have been demonstrated using various models of human and animal tumors. Studies show that LAAOs induces apoptosis in vascu‐ lar endothelial cells and inhibits angiogenesis [80]. Examples of LAAOs isolated from snake venoms with anticancer potential are a LAAO isolated from *Ophiophagus hannah* [81], ACTX-6 from *A. acutus* [82], OHAP-1 from *Trimeresurus flavoviridis* [83] and Bl-LAAO from *Bothrops leucurus* [84]. Secretory phospholipases A2 (sPLA2) also figures the snake toxins with anticancer potential [1]. sPLA2 with cytotoxic activity to tumor cells was described in *Bothrops neuwiedii* [85], *Bothrops brazili* [86], *Naja naja naja* [87], among others. Crotoxin, the main polypeptide isolated from *C. d. terrificus* has shown potent antitumor activity as well the whole venom, highlighting thereby the potential of venom as a source of pharmaceutical templates for cancer therapy [88]. BJcuL, a lectin purified from *Bothrops jararacussu* venom [89] and a metalloproteinase [90] and a lectin from *B. leucurus* [91] are other examples of tox‐ ins from snake venoms with anticancer potential.
