Isolation, structural, and functional characterization of an apoptosis-inducing L-amino acid oxidase from leaf-nosed viper (Eristocophis macmahoni) snake venom

Bothrops jararacussu Venom Inactivated by High Hydrostatic Pressure Enhances the Immunogenicity Response in Horses and Triggers Unexpected Cross-Reactivity with Other Snake Venoms

High hydrostatic pressure (HHP) has been used for viral inactivation to facilitate vaccine development when immunogenicity is maintained or even increased. In this work, we used HHP to inactivate Bothrops jararacussu venom. Our protocol promotes the loss of or decrease in many biological activities in venom. Horses were immunized with pressurized venom, and in contrast to native venom, this procedure does not induce any damage to animals. Furthermore, the serum obtained with pressurized venom efficiently neutralized all biological activities of B. jararacussu venom. Antibody titrations were higher in serum produced with pressurized venom compared to that produced by native venom, and this antivenom was not only effective against the venom of B. jararacussu but against the venom of other species and genera. In conclusion, our data show a new technique for producing hyperimmune serum using venom inactivated by HHP, and this method is associated with a reduction in toxic effects in immunized animals and higher potency.

The Role of Snake Venom Proteins in Inducing Inflammation Post-Envenomation: An Overview on Mechanistic Insights and Treatment Strategies

The intricate combination of organic and inorganic compounds found in snake venom includes proteins, peptides, lipids, carbohydrates, nucleotides, and metal ions. These components work together to immobilise and consume prey through processes such as paralysis and hypotension. Proteins, both enzymatic and non-enzymatic, form the primary components of the venom. Based on the effects they produce, venom can be classified as neurotoxic, hemotoxic, and cytotoxic. Studies have shown that, after envenomation, proteins in snake venom also contribute significantly to the induction of inflammatory responses which can either have systemic or localized consequences. This review delves into the mechanisms by which snake venom proteins trigger inflammatory responses, focusing on key families such as phospholipase A2, metalloproteinases, serine proteases, C-type lectins, cysteine-rich secretory proteins, and L-amino acid oxidase. In addition, the role of venom proteins in activating various inflammatory pathways, including the complement system, inflammasomes, and sterile inflammation are also summarized. The available therapeutic options are examined, with a focus on antivenom therapy and its side effects. In general, this review offers a comprehensive understanding of the inflammatory mechanisms that are triggered by snake venom proteins and the side effects of antivenom treatment. All these emphasize the need for effective strategies to mitigate these detrimental effects.

Identification of antigenic proteins from the venom of Malaysian snakes using immunoprecipitation assay and tandem mass spectrometry (LC-MS/MS)

Snake envenomation poses a significant risk to Malaysians and country visitors. Malaysia witnesses an estimated 650 snake bites per 100,000 population annually. The primary treatment for snake envenomation involves administering antivenom derived from horses, despite its drawbacks, such as anaphylactic reactions and serum sickness. Identifying the venom proteome is crucial for understanding and predicting the clinical implications of envenomation and developing effective treatments targeting specific venom proteins. In this study, we employ an immunoprecipitation assay followed by LC-MS/MS to identify antigenic proteins in five common venomous snakes in Malaysia compassing of two families which are pit vipers, (Calloselasma rhodostoma and Cryptelytrops purpureomaculatus) and cobras (Ophiophagus hannah, Naja kaouthia, and Naja sumatrana). The immunoprecipitation assay utilises a 2 % agarose gel, allowing antigenic proteins to diffuse and bind with antibodies in the antivenom. The antivenom utilised in this research was procured from the Queen Saovabha Memorial Institute (QSMI), Thailand, including king cobra antivenom (KCAV), cobra antivenom (CAV), Malayan pit viper antivenom (MPAV), Russell's viper antivenom (RPAV), hematopolyvalent antivenom (HPAV), neuropolyvalent antivenom (NPAV), banded krait antivenom (BKAV), and Malayan krait antivenom (MKAV). The protein identified through these interactions which are exclusive to the cobras are three-finger toxins (3FTXs) while snake C-type lectins (Snaclecs) are unique to the pit vipers. Common protein that are present in both families are L-amino acid oxidase (LAAO), Phospholipase A2 (PLA2), and snake venom metalloproteinase (SVMP). Identifying these proteins is vital for formulating a broad-spectrum antivenom applicable across multiple species.

Emerging anticancer potential and mechanisms of snake venom toxins: A review

Animal-derived venom, like snake venom, has been proven to be valuable natural resources for the drug development. Previously, snake venom was mainly investigated in its pharmacological activities in regulating coagulation, vasodilation, and cardiovascular function, and several marketed cardiovascular drugs were successfully developed from snake venom. In recent years, snake venom fractions have been demonstrated with anticancer properties of inducing apoptotic and autophagic cell death, restraining proliferation, suppressing angiogenesis, inhibiting cell adhesion and migration, improving immunity, and so on. A number of active anticancer enzymes and peptides have been identified from snake venom toxins, such as L-amino acid oxidases (LAAOs), phospholipase A2 (PLA2), metalloproteinases (MPs), three-finger toxins (3FTxs), serine proteinases (SPs), disintegrins, C-type lectin-like proteins (CTLPs), cell-penetrating peptides, cysteine-rich secretory proteins (CRISPs). In this review, we focus on summarizing these snake venom-derived anticancer components on their anticancer activities and underlying mechanisms. We will also discuss their potential to be developed as anticancer drugs in the future.

Past, Present, and Future of Naturally Occurring Antimicrobials Related to Snake Venoms

This review focuses on proteins and peptides with antimicrobial activity because these biopolymers can be useful in the fight against infectious diseases and to overcome the critical problem of microbial resistance to antibiotics. In fact, snakes show the highest diversification among reptiles, surviving in various environments; their innate immunity is similar to mammals and the response of their plasma to bacteria and fungi has been explored mainly in ecological studies. Snake venoms are a rich source of components that have a variety of biological functions. Among them are proteins like lectins, metalloproteinases, serine proteinases, L-amino acid oxidases, phospholipases type A₂, cysteine-rich secretory proteins, as well as many oligopeptides, such as waprins, cardiotoxins, cathelicidins, and β-defensins. In vitro, these biomolecules were shown to be active against bacteria, fungi, parasites, and viruses that are pathogenic to humans. Not only cathelicidins, but all other proteins and oligopeptides from snake venom have been proteolyzed to provide short antimicrobial peptides, or for use as templates for developing a variety of short unnatural sequences based on their structures. In addition to organizing and discussing an expressive amount of information, this review also describes new β-defensin sequences of Sistrurus miliarius that can lead to novel peptide-based antimicrobial agents, using a multidisciplinary approach that includes sequence phylogeny.

The secretory phenotypes of envenomed cells: Insights into venom cytotoxicity

Snake envenomation is listed as Category A Neglected Tropical Diseases (NTD) by World Health Organization, indicates a severe public health problem. The global figures for envenomation cases are estimated to be more than 1.8 million annually. Even if the affected victims survive the envenomation, they might suffer from permanent morbidity due to local envenomation. One of the most prominent local envenomation is dermonecrosis. Dermonecrosis is a pathophysiological outcome of envenomation that often causes disability in the victims due to surgical amputations, deformities, contracture, and chronic ulceration. The key venom toxins associated with this local symptom are mainly attributed to substantial levels of enzymatic and non-enzymatic toxins as well as their possible synergistic actions. Despite so, the severity of the local tissue damage is based on macroscopic observation of the bite areas. Furthermore, limited knowledge is known about the key biomarkers involved in the pathogenesis of dermonecrosis. The current immunotherapy with antivenom is also ineffective against dermonecrosis. These local effects eventually end up as sequelae. There is also a global shortage of toxins-targeted therapeutics attributed to inadequate knowledge of the actual molecular mechanisms of cytotoxicity. This chapter discusses the characterization of secretory phenotypes of dermonecrosis as an advanced tool to indicate its severity and pathogenesis in envenomation. Altogether, the secretory phenotypes of envenomed cells and tissues represent the precise characteristics of dermonecrosis caused by venom toxins.

Biological and Medical Aspects Related to South American Rattlesnake Crotalus durissus (Linnaeus, 1758): A View from Colombia

In Colombia, South America, there is a subspecies of the South American rattlesnake Crotalus durissus, C. d. cumanensis, a snake of the Viperidae family, whose presence has been reduced due to the destruction of its habitat. It is an enigmatic snake from the group of pit vipers, venomous, with large articulated front fangs, special designs on its body, and a characteristic rattle on its tail. Unlike in Brazil, the occurrence of human envenomation by C. durisus in Colombia is very rare and contributes to less than 1% of envenomation caused by snakes. Its venom is a complex cocktail of proteins with different biological effects, which evolved with the purpose of paralyzing the prey, killing it, and starting its digestive process, as well as having defense functions. When its venom is injected into humans as the result of a bite, the victim presents with both local tissue damage and with systemic involvement, including a diverse degree of neurotoxic, myotoxic, nephrotoxic, and coagulopathic effects, among others. Its biological effects are being studied for use in human health, including the possible development of analgesic, muscle relaxant, anti-inflammatory, immunosuppressive, anti-infection, and antineoplastic drugs. Several groups of researchers in Brazil are very active in their contributions in this regard. In this work, a review is made of the most relevant biological and medical aspects related to the South American rattlesnake and of what may be of importance for a better understanding of the snake C. d. cumanensis, present in Colombia and Venezuela.

Structural Determinants of the Specific Activities of an L-Amino Acid Oxidase from Pseudoalteromonas luteoviolacea CPMOR-1 with Broad Substrate Specificity

The Pseudoalteromonas luteoviolacea strain CPMOR-1 expresses a flavin adenine dinucleotide (FAD)-dependent L-amino acid oxidase (LAAO) with broad substrate specificity. Steady-state kinetic analysis of its reactivity towards the 20 proteinogenic amino acids showed some activity to all except proline. The relative specific activity for amino acid substrates was not correlated only with K_m or k_cat values, since the two parameters often varied independently of each other. Variation in K_m was attributed to the differential binding affinity. Variation in k_cat was attributed to differential positioning of the bound substrate relative to FAD that decreased the reaction rate. A structural model of this LAAO was compared with structures of other FAD-dependent LAAOs that have different substrate specificities: an LAAO from snake venom that prefers aromatic amino acid substrates and a fungal LAAO that is specific for lysine. While the amino acid sequences of these LAAOs are not very similar, their overall structures are comparable. The differential activity towards specific amino acids was correlated with specific residues in the active sites of these LAAOs. Residues in the active site that interact with the amino and carboxyl groups attached to the α-carbon of the substrate amino acid are conserved in all of the LAAOs. Residues that interact with the side chains of the amino acid substrates show variation. This provides insight into the structural determinants of the LAAOs that dictate their different substrate preferences. These results are of interest for harnessing these enzymes for possible applications in biotechnology, such as deracemization.

Pharmacological Investigation of CC-LAAO, an L-Amino Acid Oxidase from Cerastes cerastes Snake Venom

Snake venom proteins, which are responsible for deadly snakebite envenomation, induce severe injuries including neurotoxicity, myotoxicity, cardiotoxicity, hemorrhage, and the disruption of blood homeostasis. Yet, many snake-venom proteins have been developed as potential drugs for treating human diseases due to their pharmacological effects. In this study, we evaluated the use of, an L-amino acid oxidase isolated from Cerastes cerastes snake venom CC-LAAO, as a potential anti-glioblastoma drug, by investigating its in vivo and in vitro pharmacological effects. Our results showed that acute exposure to CC-LAAO at 1 and 2.5 µg/mL does not induce significant toxicity on vital organs, as indicated by the murine blood parameters including aspartate transaminase (AST), alanine transaminase (ALT), lactate dehydrogenase (LDH) activities, and creatinine levels. The histopathological examination demonstrated that only at high concentrations did CC-LAAO induce inflammation and necrosis in several organs of the test subjects. Interestingly, when tested on human glioblastoma U87 cells, CC-LAAO induced a dose-dependent apoptotic effect through the H₂O₂ generated during the enzymatic reaction. Taken altogether, our data indicated that low concentration of CC-LAAO may be safe and may have potential in the development of anti-glioblastoma agents.

Effects of venoms on neutrophil respiratory burst: a major inflammatory function

Neutrophils play a pivotal role in innate immunity and in the inflammatory response. Neutrophils are very motile cells that are rapidly recruited to the inflammatory site as the body first line of defense. Their bactericidal activity is due to the release into the phagocytic vacuole, called phagosome, of several toxic molecules directed against microbes. Neutrophil stimulation induces release of this arsenal into the phagosome and induces the assembly at the membrane of subunits of the NAPDH oxidase, the enzyme responsible for the production of superoxide anion that gives rise to other reactive oxygen species (ROS), a process called respiratory burst. Altogether, they are responsible for the bactericidal activity of the neutrophils. Excessive activation of neutrophils can lead to extensive release of these toxic agents, inducing tissue injury and the inflammatory reaction. Envenomation, caused by different animal species (bees, wasps, scorpions, snakes etc.), is well known to induce a local and acute inflammatory reaction, characterized by recruitment and activation of leukocytes and the release of several inflammatory mediators, including prostaglandins and cytokines. Venoms contain several molecules such as enzymes (phospholipase A2, L-amino acid oxidase and proteases, among others) and peptides (disintegrins, mastoporan, parabutoporin etc.). These molecules are able to stimulate or inhibit ROS production by neutrophils. The present review article gives a general overview of the main neutrophil functions focusing on ROS production and summarizes how venoms and venom molecules can affect this function.

Cytotoxicity of snake venom enzymatic toxins: phospholipase A2 and l-amino acid oxidase

The phospholipase A2 (PLA2) and l-amino acid oxidase (LAAO) are two major enzymes found in the venoms from most snake species. These enzymes have been structurally and functionally characterised for their pharmacological activities. Both PLA2 and LAAO from different venoms demonstrate considerable cytotoxic effects on cancer cells via induction of apoptosis, cell cycle arrest and suppression of proliferation. These enzymes produce more pronounced cytotoxic effects in cancer cells than normal cells, thus they can be potential sources as chemotherapeutic agents. It is proposed that PLA2 and LAAO contribute to an elevated oxidative stress due to their catalytic actions, for instance, the ability of PLA2 to produce reactive oxygen species during lipolysis and formation of H2O2 from LAAO catalytic activity which consequently lead to cell death. Nonetheless, the cell-death signalling pathways associated with exposure to these enzymatic toxins are not fully elucidated yet. Here in this review, we will discuss the cytotoxic effects of PLA2 and LAAO in relationship to their catalytic mechanisms and the underlying mechanisms of cytotoxic actions.

A comparative study on the leishmanicidal activity of the L-amino acid oxidases BjussuLAAO-II and BmooLAAO-II isolated from Brazilian Bothrops snake venoms

This study aims to examine whether two L-amino acid oxidases isolated from Bothrops snake venom (SV-LAAOs) were cytotoxic to Leishmania (Leishmania) amazonensis and Leishmania (Viannia) braziliensis, two causative agents of leishmaniasis, which is an endemic disease in tropical and subtropical countries. The SV-LAAOs BjussuLAAO-II and BmooLAAO-II were isolated from Bothrops jararacussu and Bothrops moojeni venom, respectively, through a three-step chromatography process that used molecular exclusion, hydrophobic interaction, and affinity columns. BmooLAAO-II is a new SV-LAAO isoform that we isolated in this study. The purified BjussuLAAO-II and BmooLAAO-II had high L-amino acid oxidase-specific activity: 3481.17 and 4924.77 U/mg/min, respectively. Both SV-LAAOs were strongly cytotoxic to the two Leishmania species, even at low concentrations. At the same concentration, BjussuLAAO-II and BmooLAAO-II exerted different cytotoxic effects on the parasites. We reported for the first time that the SV-LAAOs suppressed cell proliferation and altered the mitochondrial membrane potential of the two Leishmania species. Surprisingly, BjussuLAAO-II increased the intracellular reactive oxygen species production only in L. (L.) amazonensis, while BmooLAAO-II increased the intracellular reactive oxygen species production only in L. (V.) braziliensis, indicating that these SV-LAAOs had a certain specificity of action.

Recombinant expression of an l-amino acid oxidase from the fungus Hebeloma cylindrosporum in Pichia pastoris including fermentation

l‐amino acid oxidases (LAAOs) are flavoenzymes that catalyze the oxidative deamination of l‐amino acids to the corresponding α‐keto acids, ammonia, and hydrogen peroxide. Here, we show the overexpression, purification, and the characterization of LAAO4 from the fungus Hebeloma cylindrosporum in the yeast Pichia pastoris with a 9His‐tag and compare this with the recently characterized 6His‐hcLAAO4 expressed in E. coli. The expression of the enzyme with an ER‐signal sequence in P. pastoris resulted in a glycosylated, secreted protein. The enzymatic activity without activation was higher after expression in P. pastoris compared to E. coli. Due to treatment with acidic pH, a striking increase of activity could be detected for both expression systems resulting in similar specific activities after acid activation. Regarding the substrate spectrum, temperature stability, K_m, and v_max values, hcLAAO4 showed very few differences when produced in these two expression systems. A higher yield of hcLAAO4 could be obtained by fermentation.

Functional venomics of the Big-4 snakes of Pakistan

In South Asia, the "Big-4" venomous snakes Naja naja, Bungarus caeruleus, Daboia russelii, and Echis carinatus are so-called because they are the most medically important snakes in the region. Antivenom is the only effective treatment option for snakebite envenoming but antivenom is not produced domestically in Pakistan making the country reliant on polyvalent products imported from India and Saudi Arabia. The present study investigated the toxin composition and activity of the venoms of Pakistani specimens by means of proteomic and physio/pharmacological experiments. To evaluate the composition of venoms, 1D/2D-PAGE of crude venoms and RP-HPLC followed by SDS-PAGE were performed. Enzymatic, hemolytic, coagulant and platelet aggregating activities of crude venoms were assayed and were concordant with expectations based on the abundance of protein species in each. Neutralization assays were performed using Bharat polyvalent antivenom (BPAV), a product raised against venoms from Big-4 specimens from southern India. BPAV exhibited cross-reactivity against the Pakistani venoms, however, neutralization of clinically relevant activities was variable and rarely complete. Cumulatively, the presented data not only highlight geographical variations present in the venoms of the Big-4 snakes of South Asia, but also demonstrate the neutralization potential of Indian polyvalent against the venom of Pakistani specimens. Given the partial neutralization observed, it is clear that whilst BPAV is a life-saving product in Pakistan, in future it is hoped that a region-specific product might be manufactured domestically, using venoms of local snakes in the immunising mixture.

Structure-Function Studies and Mechanism of Action of Snake Venom L-Amino Acid Oxidases

Snake venom L-amino acid oxidases (SV-LAAOs) are the least studied venom enzymes. These enzymes catalyze the stereospecific oxidation of an L-amino acid to their corresponding α-keto acid with the liberation of hydrogen peroxide (H₂O₂) and ammonia (NH₃). They display various pathological and physiological activities including induction of apoptosis, edema, platelet aggregation/inhibition, hemorrhagic, and anticoagulant activities. They also show antibacterial, antiviral and leishmanicidal activity and have been used as therapeutic agents in some disease conditions like cancer and anti-HIV drugs. Although the crystal structures of six SV-LAAOs are present in the Protein Data Bank (PDB), there is no single article that describes all of them in particular. To better understand their structural properties and correlate it with their function, the current work describes structure characterization, structure-based mechanism of catalysis, inhibition and substrate specificity of SV-LAAOs. Sequence analysis indicates a high sequence identity (>84%) among SV-LAAOs, comparatively lower sequence identity with Pig kidney D-amino acid oxidase (<50%) and very low sequence identity (<24%) with bacterial LAAOs, Fugal (L-lysine oxidase), and Zea mays Polyamine oxidase (PAAO). The three-dimensional structure of these enzymes are composed of three-domains, a FAD-binding domain, a substrate-binding domain and a helical domain. The sequence and structural analysis indicate that the amino acid residues in the loops vary in length and composition due to which the surface charge distribution also varies that may impart variable substrate specificity to these enzymes. The active site cavity volume and its average depth also vary in these enzymes. The inhibition of these enzymes by synthetic inhibitors will lead to the production of more potent antivenoms against snakebite envenomation.

Cytotoxic, Anti-Proliferative and Apoptosis Activity of l-Amino Acid Oxidase from Malaysian Cryptelytrops purpureomaculatus (CP-LAAO) Venom on Human Colon Cancer Cells

The aim of this study is to investigate the potential anti-cancer activity of l-amino acid oxidase (CP-LAAO) purified from the venom of Cryptelytrops purpureomaculatus on SW480 and SW620 human colon cancer cells. Mass spectrometry guided purification was able to identify and purify CP-LAAO. Amino acid variations identified from the partial protein sequence of CP-LAAO may suggest novel variants of these proteins. The activity of the purified CP-LAAO was confirmed with o-phenyldiamine (OPD)-based spectrophotometric assay. CP-LAAO demonstrated time- and dose-dependent cytotoxic activity and the EC₅₀ value was determined at 13 µg/mL for both SW480 and SW620 cells. Significant increase of caspase-3 activity, reduction of Bcl-2 levels, as well as morphological changes consistent with apoptosis were demonstrated by CP-LAAO. Overall, these data provide evidence on the potential anti-cancer activity of CP-LAAO from the venom of Malaysian C. purpureomaculatus for therapeutic intervention of human colon cancer.

MipLAAO, a new L-amino acid oxidase from the redtail coral snake Micrurus mipartitus

L-amino acid oxidases (LAAOs) are ubiquitous enzymes in nature. Bioactivities described for these enzymes include apoptosis induction, edema formation, induction or inhibition of platelet aggregation, as well as antiviral, antiparasite, and antibacterial actions. With over 80 species, Micrurus snakes are the representatives of the Elapidae family in the New World. Although LAAOs in Micrurus venoms have been predicted by venom gland transcriptomic studies and detected in proteomic studies, no enzymes of this kind have been previously purified from their venoms. Earlier proteomic studies revealed that the venom of M. mipartitus from Colombia contains ∼4% of LAAO. This enzyme, here named MipLAAO, was isolated and biochemically and functionally characterized. The enzyme is found in monomeric form, with an isotope-averaged molecular mass of 59,100.6 Da, as determined by MALDI-TOF. Its oxidase activity shows substrate preference for hydrophobic amino acids, being optimal at pH 8.0. By nucleotide sequencing of venom gland cDNA of mRNA transcripts obtained from a single snake, six isoforms of MipLAAO with minor variations among them were retrieved. The deduced sequences present a mature chain of 483 amino acids, with a predicted pI of 8.9, and theoretical masses between 55,010.9 and 55,121.0 Da. The difference with experimentally observed mass is likely due to glycosylation, in agreement with the finding of three putative N-glycosylation sites in its amino acid sequence. A phylogenetic analysis of MmipLAAO placed this new enzyme within the clade of homologous proteins from elapid snakes, characterized by the conserved Serine at position 223, in contrast to LAAOs from viperids. MmipLAAO showed a potent bactericidal effect on S. aureus (MIC: 2 µg/mL), but not on E. coli. The former activity could be of interest to future studies assessing its potential as antimicrobial agent.

Amplification and bioinformatics analysis of conserved FAD-binding region of L-amino acid oxidase (LAAO) genes in gastropods compared to other organisms

This study aimed to investigate the conserved FAD-binding region of the L-amino acid oxidase (LAAO) genes in twelve gastropod genera commonly found in Thailand compared to those in other organisms using molecular cloning, nucleotide sequencing and bioinformatics analysis. Genomic DNA of gastropods and other invertebrates was extracted and screened using primers specific to the conserved FAD-binding region of LAAO. The amplified 143-bp fragments were cloned and sequenced. The obtained nucleotide sequences of 21 samples were aligned and phylogenetically compared to the LAAO-conserved FAD-binding regions of 210 other organisms from the NCBI database. Translated amino acid sequences of these samples were used in phylogenetics and pattern analyses. The phylogenetic trees showed clear separation of the conserved regions in fungi, invertebrates, and vertebrates. Alignment of the conserved 47-amino-acid FAD-binding region of the LAAOs showed 150 unique sequences among the 231 samples and these patterns were different from those of other flavoproteins in the amine oxidase family. An amino acid pattern analysis of five sub-regions (bFAD, FAD, FAD-GG, GG, and aGG) within the FAD-binding sequence showed high variation at the FAD-GG sub-region. Pattern analysis of secondary structures indicated the aGG sub-region as having the highest structural variation. Cluster analysis of these patterns revealed two major clusters representing the mollusc clade and the vertebrate clade. Thus, molecular phylogenetics and pattern analyses of sequence and structural variations could reflect evolutionary relatedness and possible structural conservation to maintain specific function within the FAD-binding region of the LAAOs in gastropods compared to other organisms.

Synergistic strategies of predominant toxins in snake venoms

Synergism is a significant phenomenon present in snake venoms that may be an evolving strategy to potentiate toxicities. Synergism exists between different toxins or toxin complexes in various snake venoms, with phospholipaseA₂s (PLA₂s) (toxins or subunits) the main enablers. The predominant toxins, snake venom PLA₂s, metalloproteases (SVMPs), serine proteases (SVSPs) and three-finger toxins (3FTxs), play essential roles in synergistic processes. The hypothetical mechanisms of synergistic effect can be generalized under the effects of amplification and chaperoning. The Toxicity Score is among the few quantitative methods to assess synergism. Selection of toxins involved in synergistically enhanced toxicity as the targets are important for development of novel antivenoms or inhibitors.

An Overview of l-Amino Acid Oxidase Functions from Bacteria to Mammals: Focus on the Immunoregulatory Phenylalanine Oxidase IL4I1

l-amino acid oxidases are flavin adenine dinucleotide-dependent enzymes present in all major kingdom of life, from bacteria to mammals. They participate in defense mechanisms by limiting the growth of most bacteria and parasites. A few mammalian LAAOs have been described, of which the enzyme “interleukin-4 induced gene 1” (IL4I1) is the best characterized. IL4I1 mainly oxidizes l-phenylalanine. It is a secreted enzyme physiologically produced by antigen presenting cells of the myeloid and B cell lineages and T helper type (Th) 17 cells. Important roles of IL4I1 in the fine control of the adaptive immune response in mice and humans have emerged during the last few years. Indeed, IL4I1 inhibits T cell proliferation and cytokine production and facilitates naïve CD4⁺ T-cell differentiation into regulatory T cells in vitro by limiting the capacity of T lymphocytes to respond to clonal receptor stimulation. It may also play a role in controlling the germinal center reaction for antibody production and limiting Th1 and Th17 responses. IL4I1 is expressed in tumor-associated macrophages of most human cancers and in some tumor cell types. Such expression, associated with its capacity to facilitate tumor growth by inhibiting the anti-tumor T-cell response, makes IL4I1 a new potential druggable target in the field of immunomodulation in cancer.

Proteomic Characterization and Comparison of Malaysian Tropidolaemus wagleri and Cryptelytrops purpureomaculatus Venom Using Shotgun-Proteomics

Tropidolaemus wagleri and Cryptelytrops purpureomaculatus are venomous pit viper species commonly found in Malaysia. Tandem mass spectrometry analysis of the crude venoms has detected different proteins in T. wagleri and C. purpureomaculatus. They were classified into 13 venom protein families consisting of enzymatic and nonenzymatic proteins. Enzymatic families detected in T. wagleri and C. purpureomaculatus venom were snake venom metalloproteinase, phospholipase A₂, l-amino acid oxidase, serine proteases, 5′-nucleotidase, phosphodiesterase, and phospholipase B. In addition, glutaminyl cyclotransferase was detected in C. purpureomaculatus. C-type lectin-like proteins were common nonenzymatic components in both species. Waglerin was present and unique to T. wagleri—it was not in C. purpureomaculatus venom. In contrast, cysteine-rich secretory protein, bradykinin-potentiating peptide, and C-type natriuretic peptide were present in C. purpureomaculatus venom. Composition of the venom proteome of T. wagleri and C. purpureomaculatus provides useful information to guide production of effective antivenom and identification of proteins with potential therapeutic applications.

Isolation, characterization and screening of the in vitro cytotoxic activity of a novel L-amino acid oxidase (LAAOcdt) from Crotalus durissus terrificus venom on human cancer cell lines

An L-amino acid oxidase (LAAOcdt) from Crotalus durissus terrificus venom was purified to homogeneity in a two-step procedure using molecular exclusion on Sephadex G-75, followed by Phenyl Sepharose FF chromatography. The molecular mass of the purified enzyme was 113 kDa, as determined by SDS-PAGE under reducing conditions. LAAOcdt showed amino acid homology to other L-amino acid oxidases isolated from different snake venoms. The comparative analysis of the internal peptide sequences of the NNPGILEYPVKPSEEGK fragments by LC-MS/MS spectrometry revealed 100% identity with C. durissus cumanensis LAAO. The purified protein catalyzed the oxidative deamination of L-amino acids, and the most specific substrates were L-Tyr and L-Phe. The enzyme presented optimum activity at pH 7.4 and at 44 °C. LAAOcdt also showed hemolytic activity (0.6-20 μg/μL) and induced both the formation plasma clots (5-100 μg/μL) and platelet aggregation (2.5 × 10(-3), 5.0 × 10(-3) and 10 × 10(-3) μg/mL), as well as bactericidal activity (2.5-10 μg/μL) against Staphylococcus aureus. Moreover, LAAOcdt exhibited cytotoxicity in distinct cancer cell lines, which presented a heterogeneous response profile. The mean IC50 value was 10.5 μg/mL. Glioma and pancreatic carcinoma cells were the most sensitive cell lines; they showed mean IC50 values of 7.2 μg/mL and 7.4 μg/mL, respectively. The exposure of the drug-sensitive cells to LAAOcdt for 24 h upregulated activated p-H2AX and efficiently decreased P42/P44 (ERK) activation in glioma cells (HCB151), which suggested an anti-proliferative effect. In addition, increased p21 expression was observed in SiHa cells, which showed a resistant phenotype. On the other hand, the flow cytometry and immunoblotting analyses showed that the enzyme did not induce cancer cell apoptosis. These results suggest that another cell death mechanism might contribute to the LAAOcdt-induced cytotoxicity. Taken together, this work may help to elucidate the function and structure of LAAOcdt by providing the basis for further investigations on its efficacy in cancer treatment.

p38 MAPK is involved in human neutrophil chemotaxis induced by L-amino acid oxidase from Calloselasma rhodosthoma

The action of LAAO, an L-amino acid oxidase isolated from Calloselasma rhodosthoma snake venom, on isolated human neutrophil function was investigated. Cr-LAAO showed no toxicity on neutrophils. Cr-LAAO in its native form induced the neutrophil chemotaxis, suggesting that its primary structure is essential for stimulation the cell. p38 MAPK and PI3K have a role as signaling pathways of CR-LAAO induced chemotaxis. This toxin also induced the production of hydrogen peroxide and stimulated phagocytosis in neutrophils. Furthermore, Cr-LAAO was able to stimulate neutrophils to release IL-6, IL-8, MPO, LTB4 and PGE2. Together, the data showed that the Cr-LAAO triggers relevant proinflammatory events.

Bordonein-L, a new L-amino acid oxidase from Crotalus durissus terrificus snake venom: isolation, preliminary characterization and enzyme stability

Background

Crotalus durissus terrificus venom (CdtV) is one of the most studied snake venoms in Brazil. Despite presenting several well known proteins, its L-amino acid oxidase (LAAO) has not been studied previously. This study aimed to isolate, characterize and evaluate the enzyme stability of bordonein-L, an LAAO from CdtV.

Methods

The enzyme was isolated through cation exchange, gel filtration and affinity chromatography, followed by a reversed-phase fast protein liquid chromatography to confirm its purity. Subsequently, its N-terminal amino acid sequence was determined by Edman degradation. The enzyme activity and stability were evaluated by a microplate colorimetric assay and the molecular mass was estimated by SDS-PAGE using periodic acid-Schiff staining and determined by mass spectrometry.

Results

The first 39 N-terminal amino acid residues exhibited high identity with other snake venom L-amino acid oxidases. Bordonein-L is a homodimer glycoprotein of approximately 101 kDa evaluated by gel filtration. Its monomer presents around 53 kDa estimated by SDS-PAGE and 58,702 Da determined by MALDI-TOF mass spectrometry. The enzyme exhibited maximum activity at pH 7.0 and lost about 50 % of its activity after five days of storage at 4 °C. Bordonein-L’s activity was higher than the control when stored in 2.8 % mannitol or 8.5 % sucrose.

Conclusions

This research is pioneering in its isolation, characterization and enzyme stability evaluation of an LAAO from CdtV, denominated bordonein-L. These results are important because they increase the knowledge about stabilization of LAAOs, aiming to increase their shelf life. Since the maintenance of enzymatic activity after long periods of storage is essential to enable their biotechnological use as well as their functional studies.

Heterologous expression of l-lysine α-oxidase from Scomber japonicus in Pichia pastoris and functional characterization of the recombinant enzyme

Fish have a complex self-defense mechanism against microbial invasion. Recently, l-lysine α-oxidases have been identified from a number of fish species as a novel type of antibacterial protein in the integument. These enzymes exhibit strict substrate specificity for l-lysine, but the underlying mechanisms and details of their catalytic properties remain unknown. In this study, a synthetic gene coding for Scomber japonicus l-lysine α-oxidase, originally termed AIP (for apoptosis-inducing protein), was expressed in Pichia pastoris, and the recombinant enzyme (rAIP) was purified and characterized. rAIP exhibited essentially the same substrate specificity as the native enzyme, catalyzing the oxidative deamination of l-lysine as an exclusive substrate. rAIP was N-glycosylated and remained active over a wide range of pH, with an optimal pH of 7.5. The enzyme was stable in the pH range from 4.5 to 10.0 and was thermally stable up to 60°C. A molecular modelling of rAIP and a comparative structure/sequence analysis with homologous enzymes indicate that Asp(220) and Asp(320) are the substrate-binding residues that are likely to confer exclusive substrate specificity for l-lysine on the fish enzymes.

Extreme venom variation in Middle Eastern vipers: a proteomics comparison of Eristicophis macmahonii, Pseudocerastes fieldi and Pseudocerastes persicus

Venoms of the viperid sister genera Eristicophis and Pseudocerastes are poorly studied despite their anecdotal reputation for producing severe or even lethal envenomations. This is due in part to the remote and politically unstable regions that they occupy. All species contained are sit and wait ambush feeders. Thus, this study examined their venoms through proteomics techniques in order to establish if this feeding ecology, and putatively low levels of gene flow, have resulted in significant variations in venom profile. The techniques indeed revealed extreme venom variation. This has immediate implications as only one antivenom is made (using the venom of Pseudocerastes persicus) yet the proteomic variation suggests that it would be of only limited use for the other species, even the sister species Pseudocerastes fieldi. The high degree of variation however also points toward these species being rich resources for novel compounds which may have use as lead molecules in drug design and development.

BIOLOGICAL SIGNIFICANCE

These results show extreme venom variation between these closely related snakes. These results have direct implications for the treatment of the envenomed patient.

Snake venom L-amino acid oxidases: an overview on their antitumor effects

The L-amino acid oxidases (LAAOs) constitute a major component of snake venoms and have been widely studied due to their widespread presence and various effects, such as apoptosis induction, cytotoxicity, induction and/or inhibition of platelet aggregation, hemorrhage, hemolysis, edema, as well as antimicrobial, antiparasitic and anti-HIV activities. The isolated and characterized snake venom LAAOs have become important research targets due to their potential biotechnological applications in pursuit for new drugs of interest in the scientific and medical fields. The current study discusses the antitumor effects of snake venom LAAOs described in the literature to date, highlighting the mechanisms of apoptosis induction proposed for this class of proteins.

Snake venom L-amino acid oxidases: trends in pharmacology and biochemistry

L-amino acid oxidases are enzymes found in several organisms, including venoms of snakes, where they contribute to the toxicity of ophidian envenomation. Their toxicity is primarily due to enzymatic activity, but other mechanisms have been proposed recently which require further investigation. L-amino acid oxidases exert biological and pharmacological effects, including actions on platelet aggregation and the induction of apoptosis, hemorrhage, and cytotoxicity. These proteins present a high biotechnological potential for the development of antimicrobial, antitumor, and antiprotozoan agents. This review provides an overview of the biochemical properties and pharmacological effects of snake venom L-amino acid oxidases, their structure/activity relationship, and supposed mechanisms of action described so far.

Antitumoral activity of snake venom proteins: new trends in cancer therapy

For more than half a century, cytotoxic agents have been investigated as a possible treatment for cancer. Research on animal venoms has revealed their high toxicity on tissues and cell cultures, both normal and tumoral. Snake venoms show the highest cytotoxic potential, since ophidian accidents cause a large amount of tissue damage, suggesting a promising utilization of these venoms or their components as antitumoral agents. Over the last few years, we have studied the effects of snake venoms and their isolated enzymes on tumor cell cultures. Some in vivo assays showed antineoplastic activity against induced tumors in mice. In human beings, both the crude venom and isolated enzymes revealed antitumor activities in preliminary assays, with measurable clinical responses in the advanced treatment phase. These enzymes include metalloproteases (MP), disintegrins, L-amino acid oxidases (LAAOs), C-type lectins, and phospholipases A2 (PLA2s). Their mechanisms of action include direct toxic action (PLA2s), free radical generation (LAAOs), apoptosis induction (PLA2s, MP, and LAAOs), and antiangiogenesis (disintegrins and lectins). Higher cytotoxic and cytostatic activities upon tumor cells than normal cells suggest the possibility for clinical applications. Further studies should be conducted to ensure the efficacy and safety of different snake venom compounds for cancer drug development.

Effect of L-amino acid oxidase from Calloselasma rhodosthoma snake venom on human neutrophils

The in vitro effects of LAAO, an l-amino acid oxidase isolated from Calloselasma rhodosthoma snake venom, on isolated human neutrophil function were investigated. LAAO showed no toxicity on neutrophils. At non-cytotoxic concentrations, LAAO induced the superoxide anion production by isolated human neutrophil. This toxin, in its native form, is also able to stimulate the production of hydrogen peroxide in neutrophils, suggesting that its primary structure is essential for stimulation the cell. Moreover, the incubation of LAAO and phenol red medium did not induce the production of hydrogen peroxide. Furthermore, LAAO was able to stimulate neutrophils to release proinflammatory mediators such as IL-8 and TNF-α as well as NETs liberation. Together, the data showed that the LAAO triggers relevant proinflammatory events. Particular regions of the molecule distinct from the LAAO catalytic site may be involved in the onset of inflammatory events.

Antagonism of Trichoderma harzianum ETS 323 on Botrytis cinerea mycelium in culture conditions

ABSTRACT Previous studies have shown that the extracellular proteins of Trichoderma harzianum ETS 323 grown in the presence of deactivated Botrytis cinerea in culture include a putative l-amino acid oxidase and have suggested the involvement of this enzyme in the antagonistic mechanism. Here, we hypothesized that the mycoparasitic process of Trichoderma spp. against B. cinerea involves two steps; that is, an initial hyphal coiling stage and a subsequent hyphal coiling stage, with different coiling rates. The two-step antagonism of T. harzianum ETS 323 against B. cinerea during the mycoparasitic process in culture was evaluated using a biexponential equation. In addition, an l-amino acid oxidase (Th-l-AAO) was identified from T. harzianum ETS 323. The secretion of Th-l-AAO was increased when T. harzianum ETS 323 was grown with deactivated hyphae of B. cinerea. Moreover, in vitro assays indicated that Th-l-AAO effectively inhibited B. cinerea hyphal growth, caused cytosolic vacuolization in the hyphae, and led to hyphal lysis. Th-l-AAO also showed disease control against the development of B. cinerea on postharvest apple fruit and tobacco leaves. Furthermore, an apoptosis-like response, including the generation of reactive oxygen species, was observed in B. cinerea after treatment with Th-l-AAO, suggesting that Th-l-AAO triggers programmed cell death in B. cinerea. This may be associated with the two-step antagonism of T. harzianum ETS 323 against B. cinerea.

Proteomics and deep sequencing comparison of seasonally active venom glands in the platypus reveals novel venom peptides and distinct expression profiles

The platypus is a venomous monotreme. Male platypuses possess a spur on their hind legs that is connected to glands in the pelvic region. They produce venom only during the breeding season, presumably to fight off conspecifics. We have taken advantage of this unique seasonal production of venom to compare the transcriptomes of in- and out-of-season venom glands, in conjunction with proteomic analysis, to identify previously undiscovered venom genes. Comparison of the venom glands revealed distinct gene expression profiles that are consistent with changes in venom gland morphology and venom volumes in and out of the breeding season. Venom proteins were identified through shot-gun sequenced venom proteomes of three animals using RNA-seq-derived transcripts for peptide-spectral matching. 5,157 genes were expressed in the venom glands, 1,821 genes were up-regulated in the in-season gland, and 10 proteins were identified in the venom. New classes of platypus-venom proteins identified included antimicrobials, amide oxidase, serpin protease inhibitor, proteins associated with the mammalian stress response pathway, cytokines, and other immune molecules. Five putative toxins have only been identified in platypus venom: growth differentiation factor 15, nucleobindin-2, CD55, a CXC-chemokine, and corticotropin-releasing factor-binding protein. These novel venom proteins have potential biomedical and therapeutic applications and provide insights into venom evolution.

Analysis of phospholipase A2, L-amino acid oxidase, and proteinase enzymatic activities of the Lachesis muta rhombeata venom

The study of venom components is an important step toward understanding the mechanism of action of such venoms and is indispensable for the development of new therapies. This work aimed to investigate the venom of Lachesis muta rhombeata and evaluate enzymes related to its toxicity. Phospholipase A2 (PLA(2)), L-amino acid oxidase (LAAO), and proteinase activities were measured, and the molecular weights were estimated. We found the venom to contain one PLA(2) (17 kDa), one LAAO (132 kDa), and three serine proteinases (40, 31, and 20 kDa). Although only serine proteinases were observed in the zymogram, metalloproteinases were found to contribute more to the total proteolytic activity than did serine proteinases. The work confirmed the presence of highly active enzymes; and, moreover, we proposed a novel method for confirming the presence of LAAOs by zymography. We also suggested a simple step to increase the sensitivity of proteinase assays.

Past decade study of snake venom L-amino acid oxidase

As one of the major protein (enzyme) components of snake venom (SV), L-amino acid oxidase (LAAO) plays an important role in the toxicities and biological activities for SV. Accumulated researches in the past decade gradually revealed that SV-LAAOs induce platelet aggregation, cell apoptosis and cytotoxicity, and have anti-microbial, anti-leishmaniasis, anti-tumor and anti-HIV activity. Except for the enzymatic and structural characteristics of SV-LAAOs, the biological functions of SV-LAAOs and relevant action mechanisms are also summarized and discussed in the review. This work might provide useful inputs for future studies on SV-LAAOs.

Cloning, characterization and mutagenesis of Russell's viper venom L-amino acid oxidase: Insights into its catalytic mechanism

To investigate the structure-function relationships and geographic variations of L-amino acid oxidase (LAAO) from Daboia venoms, a single LAAO (designated as DrLAO) was purified from eastern Indian Daboia russelii venom and characterized. The purified DrLAO showed subunit molecular mass of 60-64kDa; its N-terminal sequence (1-20) was identical to those of several true viper LAAOs. Its preferred substrates were hydrophobic l-amino acids and the kinetic specificities were ordered as follows: Phe, Tyr, Met, Leu, and Trp. Enzyme assay and Western blotting showed that the venom LAAO contents of D. russelii were higher than those of Daboia siamensis. DrLAO dose-dependently inhibited ADP- and collagen-induced platelet aggregation with IC(50) values of 0.27 and 0.82μM, respectively. Apparently, DrLAO may synergize with other venom components to prolong and enhance bleeding symptoms after Daboia envenoming. The full sequence of DrLAO was deduced from its cDNA sequence and then confirmed by peptide mass fingerprinting. Molecular phylogenetic analysis revealed that SV-LAAO family members could be differentiated not only by snake taxonomy but also by the variations at position 223, and they divided into H223, S223, N223, and D223 subclasses. We have further prepared recombinant DrLAO and mutants by the Pichia expression system. Mutagenic analyses of DrLAO His223 revealed that this residue bound substrates instead of serving as an essential base in the catalytic steps. Our results suggest a direct hydride transfer from substrate to FAD as the mechanism for SV-LAAOs.

L-amino acid oxidases: properties and molecular mechanisms of action

During previous decade L-amino acid oxidases (LAAO) attracted the steady interest of researchers due to their poly functional effects on different biological systems. The review summarizes information concerning the sources, structure, phisico-chemical and catalytical properties of LAAO which exhibit antibacterial, antifungal, antiprotozoal, antiviral effects as well as the ambiguous action on platelet aggregation. Special attention is devoted to the elucidation of molecular mechanisms of LAAO action. It is proposed that the unique properties of LAAO are based on their catalytic reaction, which causes the decrease of L-amino acid levels, including the essential amino acids and formation of hydrogen peroxide. The action of liberated H2O2 on cells involves the synthesis of oxygen reactive species and the development of necrotic and apoptotic pathways of cell death. The presence of carbohydrate moieties in LAAO molecules promotes their attachment to cell's surface and creation of high H2O2 local concentrations. The wide range of LAAO biological effects is undoubtedly connected with their important functional roles in the organism. In particular, it was shown that in the mice brain the LAAO-catalyzed reaction is the single pathway of L-lysine degradation, while in the mice milk LAAO carry out the antibacterial effect and in human leucocytes LAAO take part in fulfilling their defending role. Protector action may be also attributed to the oxidases from the other numerous sources: microscopic fungi, snake venoms and sea inhabitants.