Amino acid sequence of a Crotalus atrox venom metalloproteinase which cleaves type IV collagen and gelatin

A simple method to determine proteolytic activity of snake venoms

In this work, we describe an easy, simple, and cost-effective method to assess the proteolytic activity of snake venoms. The method is based on measuring the hydrolytic halo formed by gelatin radial hydrolysis following the incubation of venoms on a solid gelatin-agarose plate. Venoms from Bothrops (B.) alternatus, B. diporus, B. neuwiedi, B. jararaca, B. jararacussu, Crotalus atrox, and Trimeresurus albolabris were tested. A dose-response relationship was observed for each venom tested, with proteolytic capacity values, determined as GD (gelatinolytic dose, the dose causing a 15 mm hydrolytic halo) ranging from 21 to 222 μg. A correlation between hydrolysis and hemorrhagic activity in rat skin (minimal hemorrhagic dose) was found, with an r2 value of 0.8774 (p < 0.0001). The venoms' hydrolytic activity was significantly, though not completely, inhibited by EDTA. This methodology was also deployed to assess venom neutralization by antivenoms on the hydrolytic activity of the different venoms, demonstrating its usefulness in evaluating antivenom neutralizing capacity. The method presented is simple, cheap and useful for preliminary screening of venom proteolytic activity and its inhibition and may also predict gross differences in hemorrhagic activity, contributing to the reduction of the number of animals used for these determinations.

The Venom Composition of the Snake Tribe Philodryadini: 'Omic' Techniques Reveal Intergeneric Variability among South American Racers

Snakes of the Philodryadini tribe are included in the Dipsadidae family, which is a diverse group of rear-fanged snakes widespread in different ecological conditions, including habitats and diet. However, little is known about the composition and effects of their venoms despite their relevance for understanding the evolution of these snakes or even their impact on the occasional cases of human envenoming. In this study, we integrated venom gland transcriptomics, venom proteomics and functional assays to characterize the venoms from eight species of the Philodryadini tribe, which includes the genus Philodryas, Chlorosoma and Xenoxybelis. The most abundant components identified in the venoms were snake venom metalloproteinases (SVMPs), cysteine-rich secretory proteins (CRISPs), C-type lectins (CTLs), snake endogenous matrix metalloproteinases type 9 (seMMP-9) and snake venom serinoproteinases (SVSPs). These protein families showed a variable expression profile in each genus. SVMPs were the most abundant components in Philodryas, while seMMP-9 and CRISPs were the most expressed in Chlorosoma and Xenoxybelis, respectively. Lineage-specific differences in venom composition were also observed among Philodryas species, whereas P. olfersii presented the highest amount of SVSPs and P. agassizii was the only species to express significant amounts of 3FTx. The variability observed in venom composition was confirmed by the venom functional assays. Philodryas species presented the highest SVMP activity, whereas Chlorosoma species showed higher levels of gelatin activity, which may correlate to the seMMP-9 enzymes. The variability observed in the composition of these venoms may be related to the tribe phylogeny and influenced by their diets. In the presented study, we expanded the set of venomics studies of the Philodryadini tribe, which paves new roads for further studies on the evolution and ecology of Dipsadidae snakes.

Pictolysin-III, a Hemorrhagic Type-III Metalloproteinase Isolated from Bothrops pictus (Serpentes: Viperidae) Venom, Reduces Mitochondrial Respiration and Induces Cytokine Secretion in Epithelial and Stromal Cell Lines

From the venom of the Bothrops pictus snake, an endemic species from Peru, we recently have described toxins that inhibited platelet aggregation and cancer cell migration. In this work, we characterize a novel P-III class snake venom metalloproteinase, called pictolysin-III (Pic-III). It is a 62 kDa proteinase that hydrolyzes dimethyl casein, azocasein, gelatin, fibrinogen, and fibrin. The cations Mg²⁺ and Ca²⁺ enhanced its enzymatic activity, whereas Zn²⁺ inhibited it. In addition, EDTA and marimastat were also effective inhibitors. The amino acid sequence deduced from cDNA shows a multidomain structure that includes a proprotein, metalloproteinase, disintegrin-like, and cysteine-rich domains. Additionally, Pic-III reduces the convulxin- and thrombin-stimulated platelet aggregation and in vivo, it has hemorrhagic activity (DHM = 0.3 µg). In epithelial cell lines (MDA-MB-231 and Caco-2) and RMF-621 fibroblast, it triggers morphological changes that are accompanied by a decrease in mitochondrial respiration, glycolysis, and ATP levels, and an increase in NAD(P)H, mitochondrial ROS, and cytokine secretion. Moreover, Pic-III sensitizes to the cytotoxic BH3 mimetic drug ABT-199 (Venetoclax) in MDA-MB-231 cells. To our knowledge, Pic-III is the first SVMP reported with action on mitochondrial bioenergetics and may offer novel opportunities for promising lead compounds that inhibit platelet aggregation or ECM-cancer-cell interactions.

Platelet aggregation inhibitors from Bothrops alternatus snake venom

Snake venoms are a complex mixture of proteins and peptides that can activate/inhibit platelet aggregation. Bothrops alternatus venom include three main families: metalloproteinases (SVMPs), serinoproteinases (SVSPs) and phospholipases A₂ (PLA₂s), among other minor components. In this work, we used inhibitor cocktails (containing Na₂-EDTA, PMSF and/or pBPB) to investigate the effect of these three families and of baltergin (a PIII SVMP) on platelet aggregation by a turbidmetric method using a microplate reader. Cocktails 1 (active SVMPs) and 2 (active PLA₂s) significantly reduced aggregation induced by ristocetin and collagen and by collagen and thrombin, respectively. Cocktail 3 (active SVSPs) showed a mild activation of aggregation, indicating the content of thrombin-like enzymes (TLEs) in this venom is low. Cocktail 4 (active minor components) displayed inhibitory effect with all agonists assayed (ristocetin, ADP, collagen and thrombin) but at higher IC₅₀ values. Baltergin exhibited inhibitory effect when the catalytic domain was active for ristocetin-stimulated platelet aggregation and showed a non-enzymatic mechanism of inhibition when collagen was used as agonist. It was not able to disaggregate platelet thrombus. We conclude that B. alternatus venom is a source of natural inhibitors of platelet aggregation due to the action of SVMPs and PLA₂s. Other minor components such as C-type lectins likely contribute to the antiplatelet effect. The interest in knowing the action of venom components on platelet function lies both in the understanding of the pathophysiology of snake bite envenomation and in their biotechnological application.

Crotalus atrox venom-induced cellular toxicity: Early wound progression involves reactive oxygen species

Understanding the mechanisms that produce cellular cytotoxicity is fundamental in the field of toxicology. Cytotoxic stimuli can include organic toxins such as hemorrhagic snake venom, which can lead to secondary complications such as the development of necrotic tissue and profuse scarring. These clinical manifestations mimic cytotoxic responses induce by other organic compounds such as organic acids. We used hemorrhagic snake venom and human embryonic kidney cells (HEK 293T) as a model system to better understand the cellular responses involved in venom induced cytotoxicity. Cells stimulated with Crotalus atrox (CA) (western diamondback) venom for 4 or 10 h demonstrated significant cytotoxicity. Results from 2',7'-Dichlorodihydrofluorescein diacetate (H₂ DCF-DA) assays determine CA venom stimulation induces a robust production of reactive oxygen species (ROS) over a 3-h time course. In contrast, pretreatment with polyethylene glycol (PEG)-catalase or N-acetyl cysteine (NAC) prior to CA venom stimulation significantly blunted H₂ DCFDA fluorescence fold changes and showed greater cytoprotective effects than cells stimulated with CA venom alone. Pre- incubating HEK293T cells with the NADPH oxidase (NOX) pan-inhibitor VAS2870 prior venom stimulation significantly minimized the venom-induced oxidative burst at early timepoints (≤2 h). Collectively, our experiments show that pre-application of antioxidants reduces CA venom induce cellular toxicity. This result highlights the importance of ROS in the early stages of cytotoxicity and suggests muting ROS production in noxious injuries may increase positive clinical outcomes.

Analysis of genes encoding for proteolytic enzymes and cytotoxic proteins as virulence factors of Piscirickettsia salmonis in SHK-1 cells

Piscirickettsia salmonis is the causative agent of Piscirickettsiosis, a systemic disease generating high mortality rates in farmed salmon cultures of southern Chile. Proteolytic enzymes are important virulence factors since they play a key role in bacterial invasion and proliferation within the host. Bacteria growing in muscle tissues are known to secrete proteases, but no proteolytic enzymes have been described in P. salmonis to date. A battery of putative protease genes was found in the genomes and available strains of P. salmonis by bioinformatics analyses, and their identity was established through comparison with protease genes in databases. The transcript levels of five candidate genes were analysed by in vitro infection and qPCR. All strains were found to generate protease activity to varying degrees, and this was significantly increased when bacteria infected a salmon cell line. Gene expression of several types of proteases was also evidenced, with the highest levels corresponding to the type 1 secretion system (T1SS), which is also involved in the transport of haemolysin A, although transcripts with significant levels of peptidase M4 (thermolysin) and CLP protease were also found.

Functional Mining of the Crotalus Spp. Venom Protease Repertoire Reveals Potential for Chronic Wound Therapeutics

Chronic wounds are a major health problem that cause millions of dollars in expenses every year. Among all the treatments used, active wound treatments such as enzymatic treatments represent a cheaper and specific option with a fast growth category in the market. In particular, bacterial and plant proteases have been employed due to their homology to human proteases, which drive the normal wound healing process. However, the use of these proteases has demonstrated results with low reproducibility. Therefore, alternative sources of proteases such as snake venom have been proposed. Here, we performed a functional mining of proteases from rattlesnakes (Crotalus ornatus, C. molossus nigrescens, C. scutulatus, and C. atrox) due to their high protease predominance and similarity to native proteases. To characterize Crotalus spp. Proteases, we performed different protease assays to measure and confirm the presence of metalloproteases and serine proteases, such as the universal protease assay and zymography, using several substrates such as gelatin, casein, hemoglobin, L-TAME, fibrinogen, and fibrin. We found that all our venom extracts degraded casein, gelatin, L-TAME, fibrinogen, and fibrin, but not hemoglobin. Crotalus ornatus and C. m. nigrescens extracts were the most proteolytic venoms among the samples. Particularly, C. ornatus predominantly possessed low molecular weight proteases (P-I metalloproteases). Our results demonstrated the presence of metalloproteases capable of degrading gelatin (a collagen derivative) and fibrin clots, whereas serine proteases were capable of degrading fibrinogen-generating fibrin clots, mimicking thrombin activity. Moreover, we demonstrated that Crotalus spp. are a valuable source of proteases that can aid chronic wound-healing treatments.

Snake Venom Metalloproteinases (SVMPs): A structure-function update

Snake venom metalloproteinases (SVMPs) represent a diverse group of multi-domain proteins with several biological activities such as the ability to induce hemorrhage, proteolytic degradation of fibrinogen and fibrin, induction of apoptosis and inhibition of platelet aggregation. Due to these activities, SVMPs are responsible for many of the well-known pathological phenotypes in snake envenomations caused particularly by species from the Viperidae family and the Crotalinae subfamily. These proteins have been classified based on their size and domain structure into P–I, P-II and P-III classes. Comparatively, members of the P–I SVMPs possess the simplest structures, formed by the catalytic metalloproteinase domain only; the P-II SVMPs are moderately more complex, having the canonical disintegrin domain in addition to the metalloproteinase domain; members of the P-III class are more structurally varied, comprising the metalloproteinase, disintegrin-like, and cysteine-rich domains. Proteolytic cleavage, repeated domain loss and presence of other ancillary domains are responsible for structural diversities in the P-III class. However, studies continue to unveil the relationship between the structure and function of these proteins. In this review, we recovered evidences from literature on the structural peculiarities and functional classification of Snake Venom Metalloproteinases. In addition, we reflect on diversities that exist among each class while taking into account specific and up-to-date class-based activities.

Convergent recruitment of adamalysin-like metalloproteases in the venom of the red bark centipede (Scolopocryptops sexspinosus)

Many venom proteins have presumably been convergently recruited by taxa from diverse venomous lineages. These toxic proteins have characteristics that allow them to remain stable in solution and have a high propensity for toxic effects on prey and/or potential predators. Despite this well-established convergent toxin recruitment, some toxins seem to be lineage specific. To further investigate the toxic proteins found throughout venomous lineages, venom proteomics and venom-gland transcriptomics were performed on two individual red bark centipedes (Scolopocryptops sexspinosus). Combining the protein phenotype with the transcript genotype resulted in the first in-depth venom characterization of S. sexspinosus, including 72 venom components that were identified in both the transcriptome and proteome and 1468 nontoxin transcripts identified in the transcriptome. Ten different toxin families were represented in the venom and venom gland with the majority of the toxins belonging to metalloproteases, CAPS (cysteine-rich secretory protein, antigen 5, and pathogenesis-related 1 proteins), and β-pore-forming toxins. Nine of these toxin families shared a similar proteomic structure to venom proteins previously identified from other centipedes. However, the most highly expressed toxin family, the adamalysin-like metalloproteases, has until now only been observed in the venom of snakes. We confirmed adamalysin-like metalloprotease activity by means of in vivo functional assays. The recruitment of an adamalysin-like metalloprotease into centipede venom represents a striking case of convergent evolution.

Intraspecies geographical variability in the South American tigra mariposa (Bothrops venezuelensis Sandner 1952) snake venom activities

Bothrops venezuelensis snake venoms, from five localities in the North-Central Venezuelan regions, showed biochemical and haemostatic differences. In this study, bioactivities of B. venezuelensis venoms from different regions (Aragua state; Waraira Repano (Capital District); Baruta, La Boyera and Lagunetica (Miranda state)) were compared using both natural and synthetic substrates. The protein contents of these venoms were Lagunetica 89%, La Boyera 79%, Baruta 71%, Waraira Repano 68% and Aragua 64%. Toxic activities effects were: Intraperitoneal LD50s: Aragua-14 mg/kg; Waraira Repano-6.4 mg/kg; Baruta: 8.3 mg/kg; La Boyera-4.4 mg/kg; Lagunetica-16.2 mg/kg. The MHD results: Aragua-21.4 μg/mouse; Waraira Repano-2.5 μg/mouse; Baruta-1.2 μg/mouse; La Boyera-1.4 μg/mouse and Lagunetica-12 μg/mouse. The hide powder azure results: Aragua-1.24 U/mg; La Boyera-2.26 U/mg; Baruta-2.83 U/mg; Lagunetica-3.28 U/mg and Waraira Repano-5.77 U/mg. Esterase specific activity on BAEE results: Waraira Repano-666.66 U/mg; La Boyera-805.5 U/mg; Baruta-900.00 U/mg; Lagunetica-922.19 U/mg and Aragua-1960.67 U/mg. Casein zymography showed digestion bands in the molecular weight above 100 and at 66.2 and 21.5 kDa. Analysis of casein degradation by SDS-PAGE showed two different degradation patterns. Fibrinolytic activity (mm2/μg) on fibrin plates results: Aragua-6.07; Lagunetica-27.6; Waraira Repano-35.7; La Boyera-44.27 and Baruta-45.63. In the fibrinogenolytic assay, the five venoms completely degraded the α chain after 1 min of incubation. None of the venoms completely degraded the β and γ chains after 24 h incubation. The research indicated that venoms of B. venezuelensis of different geographic areas in Venezuela exhibit variances in composition and component concentrations; except the Aragua venom, all of them had high proteolytic activities.

Insights into the Mechanisms Involved in Strong Hemorrhage and Dermonecrosis Induced by Atroxlysin-Ia, a PI-Class Snake Venom Metalloproteinase

Hemorrhage is the most prominent effect of snake venom metalloproteinases (SVMPs) in human envenomation. The capillary injury is a multifactorial effect caused by hydrolysis of the components of the basement membrane (BM). The PI and PIII classes of SVMPs are abundant in viperid venoms and hydrolyze BM components. However, hemorrhage is associated mostly with PIII-class SVMPs that contain non-catalytic domains responsible for the binding of SVMPs to BM proteins, facilitating enzyme accumulation in the tissue and enhancing its catalytic efficiency. Here we report on Atroxlysin-Ia, a PI-class SVMP that induces hemorrhagic lesions in levels comparable to those induced by Batroxrhagin (PIII-class), and a unique SVMP effect characterized by the rapid onset of dermonecrotic lesions. Atroxlysin-Ia was purified from B. atrox venom, and sequence analyses indicated that it is devoid of non-catalytic domains and unable to bind to BM proteins as collagen IV and laminin in vitro or in vivo. The presence of Atroxlysin-Ia was diffuse in mice skin, and localized mainly in the epidermis with no co-localization with BM components. Nevertheless, the skin lesions induced by Atroxlysin-Ia were comparable to those induced by Batroxrhagin, with induction of leukocyte infiltrates and hemorrhagic areas soon after toxin injection. Detachment of the epidermis was more intense in skin injected with Atroxlysin-Ia. Comparing the catalytic activity of both toxins, Batroxrhagin was more active in the hydrolysis of a peptide substrate while Atroxlysin-Ia hydrolyzed more efficiently fibrin, laminin, collagen IV and nidogen. Thus, the results suggest that Atroxlysin-Ia bypasses the binding step to BM proteins, essential for hemorrhagic lesions induced by PII- and P-III class SVMPs, causing a significantly fast onset of hemorrhage and dermonecrosis, due to its higher proteolytic capacity on BM components.

A Comprehensive View of the Structural and Functional Alterations of Extracellular Matrix by Snake Venom Metalloproteinases (SVMPs): Novel Perspectives on the Pathophysiology of Envenoming

Snake venom metalloproteinases (SVMPs) affect the extracellular matrix (ECM) in multiple and complex ways. Previously, the combination of various methodological platforms, including electron microscopy, histochemistry, immunohistochemistry, and Western blot, has allowed a partial understanding of such complex pathology. In recent years, the proteomics analysis of exudates collected in the vicinity of tissues affected by SVMPs has provided novel and exciting information on SVMP-induced ECM alterations. The presence of fragments of an array of ECM proteins, including those of the basement membrane, has revealed a complex pathological scenario caused by the direct action of SVMPs. In addition, the time-course analysis of these changes has underscored that degradation of some fibrillar collagens is likely to depend on the action of endogenous proteinases, such as matrix metalloproteinases (MMPs), synthesized as a consequence of the inflammatory process. The action of SVMPs on the ECM also results in the release of ECM-derived biologically-active peptides that exert diverse actions in the tissue, some of which might be associated with reparative events or with further tissue damage. The study of the effects of SVMP on the ECM is an open field of research which may bring a renewed understanding of snake venom-induced pathology.

Isolation and Characterization of a 32-kDa Fibrinolytic Enzyme (FE-32kDa) from Gloydius blomhoffii siniticus Venom: Fibrinolytic Enzyme from Gloydius blomhoffii siniticus Venom

Objectives:

This study was undertaken to isolate a fibrinolytic enzyme from the snake venom of Gloydius blomhoffii siniticus and to investigate its enzymatic characteristics and hemorrhagic activity as a potential pharmacopuncture agent.

Methods:

The fibrinolytic enzyme was isolated by using chromatography, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and fibrin plate assay. The characteristics of the enzyme were investigated using fibrin plate assay, protein hydrolysis analysis, and hemorrhage assay. Its amino acid composition was determined.

Results:

The fibrinolytic enzyme with the molecular weight of 32kDa (FE-32kDa) from Gloydius blomhoffii siniticus showed a fibrin hydrolysis zone at the concentration of 0.2 mg/mL in the fibrin plate assay. The fibrin hydrolysis activity of the enzyme was inhibited completely by ethylenediaminetetraacetic acid (EDTA), ethyleneglycoltetraacetic acid (EGTA), and 1, 10-phenanthroline, thiothreitol and cysteine, and partially by phenylmethanesulfonylfluoride (PMSF). Metal ions such as Fe²⁺ and Hg²⁺ inhibited the fibrin hydrolysis completely, but Zn²⁺ enhanced it. FE-32kDa hydrolyzed α-chain but did not hydrolyze β-chain and γ-chain of fibrinogen. High-molecular-weight polypeptides of gelatin were hydrolyzed partially into low-molecular-weight polypeptides, but the extent of hydrolysis was limited. FE-32kDa induced hemorrhage beneath back skin of mice at the dose of 2 μg.

Conclusions:

FE-32kDa is a α-fibrin(ogen)olytic metalloprotease that requires Zn²⁺ for fibrinolytic activity and causes hemorrhage, suggesting that the enzyme is not appropriate for use as a clinical pharmacopuncture.

Okinalysin, a novel P-I metalloproteinase from Ovophis okinavensis: biological properties and effect on vascular endothelial cells

A novel hemorrhagic metalloproteinase, okinalysin, was isolated from the venom of Ovophis okinavensis. It possessed caseinolytic and hemorrhagic activities, and also hydrolyzed fibrinogen and collagen. These activities were inhibited by ethylenediaminetetraacetic acid (EDTA) but not by p-amidinophenyl methanesulfonyl fluoride hydrochloride (APMSF). The molecular mass of okinalysin was 22,202 Da measured by MALDI/TOF mass spectrometry. The primary structure of okinalysin was partially determined by Edman sequencing, and the putative zinc-binding domain HEXXHXXGXXH was found to be present in its structure. From these data, okinalysin is defined as a metalloproteinase belonging to a P-I class. The partial amino acid sequence of okinalysin was homologous to the C-terminus of MP 10, a putative metalloproteinase induced from transcriptome of the venom gland cDNA sequencing of O. okinavensis. Okinalysin possessed cytotoxic activity on cultured endothelial cells, and the EC50 on human pulmonary artery endothelial cells was determined to be 0.6 μg/mL. The histopathological study also showed that okinalysin causes the leakage of red blood cells and neutrophil infiltration. These results indicate that destruction of blood vessels by okinalysin is one of the main causes of hemorrhage.

Snake venom metalloproteinases

Recent proteomic analyses of snake venoms show that metalloproteinases represent major components in most of the Crotalid and Viperid venoms. In this chapter we discuss the multiple activities of the SVMPs. In addition to hemorrhagic activity, members of the SVMP family also have fibrin(ogen)olytic activity, act as prothrombin activators, activate blood coagulation factor X, possess apoptotic activity, inhibit platelet aggregation, are pro-inflammatory and inactivate blood serine proteinase inhibitors. Clearly the SVMPs have multiple functions in addition to their well-known hemorrhagic activity. The realization that there are structural variations in the SVMPs and the early studies that led to their classification represents an important event in our understanding of the structural forms of the SVMPs. The SVMPs were subdivided into the P-I, P-II and P-III protein classes. The noticeable characteristic that distinguished the different classes was their size (molecular weight) differences and domain structure: Class I (P-I), the small SVMPs, have molecular masses of 20-30 kDa, contain only a pro domain and the proteinase domain; Class II (P-II), the medium size SVMPs, molecular masses of 30-60 kDa, contain the pro domain, proteinase domain and disintegrin domain; Class III (P-III), the large SVMPs, have molecular masses of 60-100 kDa, contain pro, proteinase, disintegrin-like and cysteine-rich domain structure. Another significant advance in the SVMP field was the characterization of the crystal structure of the first P-I class SVMP. The structures of other P-I SVMPs soon followed and the structures of P-III SVMPs have also been determined. The active site of the metalloproteinase domain has a consensus HEXXHXXGXXHD sequence and a Met-turn. The "Met-turn" structure contains a conserved Met residue that forms a hydrophobic basement for the three zinc-binding histidines in the consensus sequence.

Hemorrhagic activity of HF3, a snake venom metalloproteinase: insights from the proteomic analysis of mouse skin and blood plasma

Hemorrhage induced by snake venom metalloproteinases (SVMPs) is a complex phenomenon resulting in capillary disruption and blood extravasation. The mechanism of action of SVMPs has been investigated using various methodologies however the precise molecular events associated with microvessel disruption remains not fully understood. To gain insight into the hemorrhagic process, we analyzed the global effects of HF3, an extremely hemorrhagic SVMP from Bothrops jararaca, in the mouse skin and plasma. We report that in the HF3-treated skin there was evidence of degradation of extracellular matrix (collagens and proteoglycans), cytosolic, cytoskeleton, and plasma proteins. Furthermore, the data suggest that direct and indirect effects promoted by HF3 contributed to tissue injury as the activation of collagenases was detected in the HF3-treated skin. In the plasma analysis after depletion of the 20 most abundant proteins, fibronectin appeared as degraded by HF3. In contrast, some plasma proteinase inhibitors showed higher abundance compared to control skin and plasma. This is the first study to assess the complex in vivo effects of HF3 using high-throughput proteomic approaches, and the results underscore a scenario characterized by the interplay between the hydrolysis of intracellular, extracellular, and plasma proteins and the increase of plasma inhibitors in the hemorrhagic process.

Isolation and biochemical characterization of rubelase, a non-hemorrhagic elastase from Crotalus ruber ruber (Red Rattlesnake) venom

A novel non-hemorrhagic basic metalloprotease, rubelase, was isolated from the venom of Crotalus ruber ruber. Rubelase hydrolyzes succinyl-L-alanyl-L-alanyl-L-alanyl p-nitroanilide (STANA), a specific substrate for elastase, and the hydrolytic activity was inhibited by chelating agents. It also hydrolyzes collagen and fibrinogen. However, hemorrhagic activity was not observed. By ESI/Q-TOF and MALDI/TOF mass spectrometry combined with Edman sequencing procedure, the molecular mass of rubelase was determined to be 23,266 Da. Although its primary structure was similar to rubelysin (HT-2), a hemorrhagic metalloprotease isolated from the same snake venom, the circumstances surrounding putative zinc binding domain HEXXHXXGXXH were found to be different when the three-dimensional computer models of both metalloproteases were compared. The cytotoxic effects of rubelase and rubelysin on cultured endothelial and smooth muscle cells were also different, indicating that the substitution of several amino acid residues causes the changes of active-site conformation and cell preference.

Purification and characterization of a metalloproteinase, Porthidin-1, from the venom of Lansberg's hog-nosed pitvipers (Porthidium lansbergii hutmanni)

Porthidium lansbergii hutmanni is a small pit viper found on Margarita Island, Venezuela. Local tissue damage is one of the most obvious characteristics of P. l. hutmanni envenomation, which can lead to diverse pathological effects, such as hemorrhage, edema, blistering, necrosis, lymphatic vessel damage and degradation of extracellular matrix. Metalloproteinases are one of the major components in venoms responsible for these effects. To date, very little is known or has been reported on P. l. hutmanni venom. Crude P. l. hutmanni venom had a LD(50) of 2.5 mg/kg and was considered very hemorrhagic (minimal hemorrhagic dose [MHD]: 0.98 μg) when compared to other hemorrhagic (Bothrops) venoms in Venezuela. Crude P. l. hutmanni venom also inhibited ADP-induced platelet aggregation. A metalloproteinase, Porthidin-1, from this venom was isolated by three chromatography steps (Sephadex G100, Superose 12 HR10/30 and Bioscale Q2). Porthidin-1 falls in the SVMP P-I class having a molecular weight of 23 kDa, verified by both SDS-PAGE and mass spectrometry. High-resolution mass spectrometry and a database search identified a peptide from Porthidin-1 (YNGDLDK) belonging to the SVMP family of proteins. Porthidin-1 contained hemorrhagic, fibrino(geno)lytic, caseinolytic and gelatinolytic activities, and these activities were capable of being neutralized by metalloproteinase inhibitors but not serine proteinase inhibitors. The peptide YNGDLDK shared similarities with five venom proteins with a BLAST e-value of <1. This work details the biochemical and pathophysiological effects that can result from envenomations, and highlights the importance and significance for characterizing unknown or poorly documented venoms from different geographical regions.

Insights into and speculations about snake venom metalloproteinase (SVMP) synthesis, folding and disulfide bond formation and their contribution to venom complexity

As more data are generated from proteome and transcriptome analyses of snake venoms, we are gaining an appreciation of the complexity of the venoms and, to some degree, the various sources of such complexity. However, our knowledge is still far from complete. The translation of genetic information from the snake genome to the transcriptome and ultimately the proteome is only beginning to be appreciated, and will require significantly more investigation of the snake venom genomic structure prior to a complete understanding of the genesis of venom composition. Venom complexity, however, is derived not only from the venom genomic structure but also from transcriptome generation and translation and, perhaps most importantly, post-translation modification of the nascent venom proteome. In this review, we examine the snake venom metalloproteinases, some of the predominant components in viperid venoms, with regard to possible synthesis and post-translational mechanisms that contribute to venom complexity. The aim of this review is to highlight the state of our knowledge on snake venom metalloproteinase post-translational processing and to suggest testable hypotheses regarding the cellular mechanisms associated with snake venom metalloproteinase complexity in venoms.

Interaction of the cysteine-rich domain of snake venom metalloproteinases with the A1 domain of von Willebrand factor promotes site-specific proteolysis of von Willebrand factor and inhibition of von Willebrand factor-mediated platelet aggregation

Snake venom metalloproteinases (SVMPs) have recently been shown to interact with proteins containing von Willebrand factor A (VWA) domains, including the extracellular matrix proteins collagen XII, collagen XIV, matrilins 1, 3 and 4, and von Willebrand factor (VWF) via their cysteine-rich domain. We extended those studies using surface plasmon resonance to investigate the interaction of SVMPs with VWF, and demonstrated that jararhagin, a PIII SVMP containing a metalloproteinase domain followed by disintegrin-like and cysteine-rich domains, catrocollastatin C, a disintegrin-like/cysteine-rich protein, and the recombinant cysteine-rich domain of atrolysin A (A/C) all interacted with immobilized VWF in a dose-dependent fashion. Binding of VWF in solution to immobilized A/C was inhibited by ristocetin and preincubation of platelets with A/C abolished ristocetin/VWF-induced platelet aggregation, indicating that the interaction of A/C with VWF is mediated by the VWA1 domain. Jararhagin cleaved VWF at sites adjacent to the VWA1 domain, whereas atrolysin C, a SVMP lacking the cysteine-rich domain, cleaved VWF at dispersed sites. A/C and catrocollastatin C completely inhibited the digestion of VWF by jararhagin, demonstrating that the specific interaction of jararhagin with VWF via the VWA1 domain is necessary for VWF proteolysis. In summary, we localized the binding site of PIII SVMPs in VWF to the A1 domain. This suggests additional mechanisms by which SVMPs may interfere with the adhesion of platelets at the site of envenoming. Thus, specific interaction of cysteine-rich domain-containing SVMPs with VWF may function to promote the hemorrhage caused by SVMP proteolysis of capillary basements and surrounding stromal extracellular matrix.

Brain-Specific Aminopeptidase: From Enkephalinase to Protector Against Neurodegeneration

The major breakthrough discovery of enkephalins as endogenous opiates led our attempts to determine their inactivation mechanisms. Because the NH2-terminal tyrosine is absolutely necessary for the neuropeptides to exert analgesic effects, and aminopeptidase activities are extraordinarily high in the brain, a specific "amino-enkephalinase" should exist. Several aminopeptidases were identified in the central nervous system during the search. In fact, our laboratory found two novel neuron-specific aminopeptidases: NAP and NAP-2. NAP is the only functionally active brain-specific enzyme known. Its synaptic location coupled with its limited substrate specificity could constitute a "functional" specificity and contribute to enkephalin-specific functions. In addition, NAP was found to be essential for neuron growth, differentiation, and death. Thus, aminopeptidases are likely important for mental health and neurological diseases. Recently, puromycin-sensitive aminopeptidase (PSA) was identified as a modifier of tau-induced neurodegeneration. Because the enzymatic similarity between PSA and NAP, we believe that the depletion of NAP in Alzheimer's disease (AD) brains plays a causal role in the development of AD pathology. Therefore, use of the puromycin-sensitive neuron-aminopeptidase NAP could provide neuroprotective mechanisms in AD and similar neurodegenerative diseases.

Molecular characterization and comparative study of 6 salivary gland metalloproteases from the hard tick, Haemaphysalis longicornis

Six genes encoding metalloproteases were identified from the salivary gland of the hard tick, Haemaphysalis longicornis. Comparative analyses have shown the evolutionary distinct and different mRNA expression patterns of each gene during blood feeding. The proteins are synthesized as proenzymes with a prodomain and a metalloprotease/cysteine-rich domain of the reprolysin family. Within the active site, amino acid substitutions were observed. The recombinant Escherichia coli expression of one gene, hlESTMP1, was performed. The immunoblot analysis and indirect fluorescent assay using anti-hlESTMP1 suggested that this protein is mainly expressed in the cytoplasm of the salivary glands and only the mature form of 34 kDa was detectable. The proenzyme expressed by baculovirus was processed into a mature domain, suggesting that proenzyme activation possibly occurs through a pro-protein convertase dependent pathway. The presence of these diverse enzymes might contribute to the greater functional complexity of bioactive molecules in tick saliva to facilitate blood feeding.

Substrate Conformation Modulates Aggrecanase (ADAMTS-4) Affinity and Sequence Specificity

Protease-substrate interactions are governed by a variety of structural features. Although the substrate sequence specificities of numerous proteases have been established, "topological specificities," whereby proteases may be classified based on recognition of distinct three-dimensional structural motifs, have not. The aggrecanase members of the ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) family cleave a variety of proteins but do not seem to possess distinct sequence specificities. In the present study, the topological substrate specificity of ADAMTS-4 (aggrecanase-1) was examined using triple-helical or single-stranded poly(Pro) II helical peptides. Substrate topology modulated the affinity and sequence specificity of ADAMTS-4 with K(m) values indicating a preference for triple-helical structure. In turn, non-catalytic ADAMTS-4 domains were critical for hydrolysis of triple-helical and poly(Pro) II helical substrates. Comparison of ADAMTS-4 with MMP-1 (collagenase 1), MMP-13 (collagenase 3), trypsin, and thermolysin using triple-helical peptide (THP) and single-stranded peptide (SSP) substrates demonstrated that all five proteases possessed efficient "triple-helical peptidase" activity and fell into one of two categories: (k(cat)/K(m))(SSP) > (k(cat)/K(m))(THP) (thermolysin, trypsin, and MMP-13) or (k(cat)/K(m))(THP) > or = (k(cat)/K(m))(SSP) and (K(m))(SSP) > (K(m))(THP) (MMP-1 and ADAMTS-4). Overall these results suggest that topological specificity may be a guiding principle for protease behavior and can be utilized to design specific substrates and inhibitors. The triple-helical and single-stranded poly(Pro) II helical peptides represent the first synthetic substrates successfully designed for aggrecanases.

Neuropeptidases

Neuropeptides are neurotransmitters and modulators distributed in the central nervous system (CNS) and peripheral nervous system. Their abnormalities cause neurological and mental diseases. Neuropeptidases are enzymes crucial for the biosynthesis and biodegradation of neuropeptides. We here focus on the peptidases involved in the metabolism of the well-studied opioid peptides. Bioactive enkephalins are formed from propeptides by processing enzymes—prohormone thiol protease, prohormone convertase 1 and 2 (PC 1 and 2), carboxypeptidase H/E, and Arg/Lys aminopeptidase. After they exert their biological effects, enkephalins are likely to be inactivated by degrading enzymes—angiotensin-converting enzyme (ACE), aminopeptidase N (APN), puromycin-sensitive aminopeptidase (PSA), and endopeptidase 24.11. Recently, a neuron-specific aminopeptidase (NAP), which was a putative enkephalin-inactivating enzyme at the synapses, was found. Neuropeptidases are useful drug targets and their inhibitors can be therapeutic. Synthetic anti-enkephalinases and anti-aminopeptidases are being developed. They are potent analgesics but have fewer side effects than the opiates.

The cysteine-rich domain of snake venom metalloproteinases is a ligand for von Willebrand factor A domains: role in substrate targeting

Snake venom metalloproteinases (SVMPs) are members of the Reprolysin family of metalloproteinases to which the ADAM (a disintegrin and metalloproteinase) proteins also belong. The disintegrin-like/cysteine-rich domains of the ADAMs have been implicated in their function. In the case of the SVMPs, we hypothesized that these domains could function to target the metalloproteinases to key extracellular matrix proteins or cell surface proteins. Initially we detected interaction of collagen XIV, a fibril-associated collagen with interrupted triple helices containing von Willebrand factor A (VWA) domains, with the PIII SVMP catrocollastatin. Next we investigated whether other VWA domain-containing matrix proteins could support the binding of PIII SVMPs. Using surface plasmon resonance, the PIII SVMP jararhagin and a recombinant cysteine-rich domain from a PIII SVMP were demonstrated to bind to collagen XIV, collagen XII, and matrilins 1, 3, and 4. Jararhagin was shown to cleave these proteins predominantly at sites localized at or near the VWA domains suggesting that it is the VWA domains to which the PIII SVMPs are binding via their cysteine-rich domain. In light of the fact that these extracellular matrix proteins function to stabilize matrix, targeting the SVMPs to these proteins followed by their specific cleavage could promote the destabilization of extracellular matrix and cell-matrix interactions and in the case of capillaries could contribute to their disruption and hemorrhage. Although there is only limited structural homology shared by the cysteine-rich domains of the PIII SVMPs and the ADAMs our results suggest an analogous function for the cysteine-rich domains in certain members of the expanded ADAM family of proteins to target them to VWA domain-containing proteins.

Snake venom metalloproteases--structure and function of catalytic and disintegrin domains

Snake venoms are relevant sources of toxins that have evolved towards the engineering of highly active compounds. In the last years, research efforts have produced great advance in their understanding and uses. Metalloproteases with disintegrin domains are among the most abundant toxins in many Viperidae snake venoms. This review will focus on the structure, function and possible applications of the metalloprotease and disintegrin domains.

Function of the cysteine-rich domain of the haemorrhagic metalloproteinase atrolysin A: targeting adhesion proteins collagen I and von Willebrand factor

The cysteine-rich domain of the haemorrhagic metalloproteinase atrolysin A was shown to inhibit collagen-stimulated platelet aggregation and to interact with MG-63 osteosarcoma cells via integrin alpha2beta1 to inhibit adhesion to collagen I. In addition, we demonstrate by solid-phase binding assays that atrolysin A binds to collagen I and to vWF (von Willebrand factor) via exosites in the cysteine-rich domain. Interestingly, the binding site of the cysteine-rich domain on collagen I is distinct from the cell adhesion site, since the incubation of collagen-I-coated plates with the cysteine-rich domain did not prevent the adhesion of MG-63 cells to collagen. Finally, we show by surface plasmon resonance (BIAcore) analyses that the cysteine-rich domain can block vWF binding to collagen I as well as the binding of collagen I to vWF. Taken together, these results indicate that this domain may function as a cell-surface-receptor-binding site and/or a substrate recognition exosite and may thus play a role in the pathologies associated with atrolysin A.

A multifaceted analysis of viperid snake venoms by two-dimensional gel electrophoresis: an approach to understanding venom proteomics

The complexity of Viperid venoms has long been appreciated by investigators in the fields of toxinology and medicine. However, it is only recently that the depth of that complexity has become somewhat quantitatively and qualitatively appreciated. With the resurgence of two-dimensional gel electrophoresis (2-DE) and the advances in mass spectrometry virtually all venom components can be visualized and identified given sufficient effort and resources. Here we present the use of 2-DE for examining venom complexity as well as demonstrating interesting approaches to selectively delineate subpopulations of venom proteins based on particular characteristics of the proteins such as antibody cross-reactivity or enzymatic activities. 2-DE comparisons between venoms from different species of the same genus (Bothrops) of snake clearly demonstrated both the similarity as well as the apparent diversity among these venoms. Using liquid chromatography/tandem mass spectrometry we were able to identify regions of the two-dimensional gels from each venom in which certain classes of proteins were found. 2-DE was also used to compare venoms from Crotalus atrox and Bothrops jararaca. For these venoms a variety of staining/detection protocols was utilized to compare and contrast the venoms. Specifically, we used various stains to visualize subpopulations of the venom proteomes of these snakes, including Coomassie, Silver, Sypro Ruby and Pro-Q-Emerald. Using specific antibodies in Western blot analyses of 2-DE of the venoms we have examined subpopulations of proteins in these venoms including the serine proteinase proteome, the metalloproteinase proteome, and the phospholipases A2 proteome. A functional assessment of the gelatinolytic activity of these venoms was also performed by zymography. These approaches have given rise to a more thorough understanding of venom complexity and the toxins comprising these venoms and provide insights to investigators who wish to focus on these venom subpopulations of proteins in future studies.

Structural considerations of the snake venom metalloproteinases, key members of the M12 reprolysin family of metalloproteinases

The importance of proteinases in the pathologies associated with Viperid envenoming has long been appreciated. Over the past 40 years substantial research has clearly implicated metalloproteinases in the venom (snake venom metalloproteinases; SVMPs) as playing key roles in the development of such symptoms as hemorrhage, edema, hypotension, hypovolemia, inflammation and necrosis. In spite of this wealth of information there are still many unresolved questions pertaining to the structural basis for the various SVMPS giving rise to the diversity of activities. In this short review we will not attempt to provide an exhaustive collation of structural studies on the SVMPs; however, we will give a brief outline of the structural classification of the SVMPs; as well as relate them to the other members of the reprolysin family of metalloproteinases, the ADAMs. The information put forth in the text does not allow specific conclusions to be drawn on the structural basis for SVMP functional diversity, but it is our goal that it will allow for the development of testable hypotheses that can be experimentally pursued. What the reader will observe is that there are very interesting structural features displayed by the various SVMP classes and subclasses that provide insight into their functional characteristics.

A biochemical and pharmacological examination of Rhamphiophis oxyrhynchus (Rufous beaked snake) venom

The venom of R. oxyrhynchus, a member of the psammophiine subfamily of the colubrid assemblage, was examined for biological activity using biochemical and pharmacological techniques. Venom displayed a high protein content, a complex electrophorectic profile and PLA2 activity but no detectable proteolytic or haematological activities. In the chick biventer cervicis nerve muscle preparation, venom (1-10 microg/ml) displayed postsynaptic neurotoxic activity as evidenced by inhibition of indirect (0.1 Hz, 0.2 ms, supramaximal V) twitches and responses to exogenous acetylcholine (1 mM) and carbachol (20 microM). This inhibitory effect was poorly reversible by washing. Venom (30-50 microg/ml) caused a rapid and readily reversible inhibition of direct (0.1 Hz, 2 ms, supramaximal V) twitches of the chick biventer cervicis nerve muscle preparation without morphological changes to the muscle fibers. Venom (30-100 microg/ml) inhibited electrically-evoked (0.2 Hz, 0.3 ms, 70-100 V) twitches of the prostatic segment of the rat vas deferens. This inhibitory effect was not significantly attenuated by 8-phenyltheophylline (8-PT; 20 microM), idazoxan (1 microM), a combination of ranitidine (0.2 microM) and thioperamide (10 microM) or capsazepine (10 microM). Venom (5 mg/kg) induced hypotension with subsequent cardiovascular collapse in the anaesthetised rat. The cardiovascular collapse was prevented by artificial respiration of the animals prior to venom administration. The biological activities demonstrated by R. oxyrhynchus venom may aid in prey envenomation strategies such as prey immobilisation. This study provides further evidence that colubrid venoms are comprised of multiple components which can display a variety of actions, some of which may be novel, therefore reinforcing the largely untapped potential of colubrid venoms.

ADAM 12 Cleaves Extracellular Matrix Proteins and Correlates with Cancer Status and Stage

ADAM 12 is a member of a family of disintegrin-containing metalloproteases that have been implicated in a variety of diseases including Alzheimer's disease, arthritis, and cancer. We purified ADAM 12 from the urine of breast cancer patients via Q-Sepharose anion exchange and gelatin-Sepharose affinity chromatography followed by protein identification by matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Four peptides were identified that spanned the amino acid sequence of ADAM 12. Immunoblot analysis using ADAM 12-specific antibodies detected an approximately 68-kDa band identified as the mature form of ADAM 12. To characterize catalytic properties of ADAM 12, full-length ADAM 12-S was expressed in COS-7 cells and purified. Substrate specificity studies demonstrated that ADAM 12-S degrades gelatin, type IV collagen, and fibronectin but not type I collagen or casein. Gelatinase activity of ADAM 12 was completely abrogated by zinc chelators 1,10-phenanthroline and EDTA and was partially inhibited by the hydroxamate inhibitor Marimastat. Endogenous matrix metalloprotease inhibitor TIMP-3 inhibited activity. To validate our initial identification of this enzyme in human urine, 117 urine samples from breast cancer patients and controls were analyzed by immunoblot. The majority of samples from cancer patients were positive for ADAM 12 (67 of 71, sensitivity 0.94) compared with urine from controls in which ADAM 12 was detected with significantly lower frequency. Densitometric analyses of immunoblots demonstrated that ADAM 12 protein levels were higher in urine from breast cancer patients than in control urine. In addition, median levels of ADAM 12 in urine significantly increased with disease progression. These data demonstrate for the first time that ADAM 12 is a gelatinase, that it can be detected in breast cancer patient urine, and that increased urinary levels of this protein correlate with breast cancer progression. They further support the possibility that detection of urinary ADAM 12 may prove useful in the development of noninvasive diagnostic and prognostic tests for breast and perhaps other cancers.

Inhibitory potential of Crotalus durissus terrificus venom on measles virus growth

This paper presents the antiviral activity found in a snake with Crotalus durissus terrificus venom (Cdt), studied by use of microplate inhibition assay, using measles virus (MV). Cdt at concentrations below 100 microg/ml showed no cytotoxicity for Vero cells. This study shows the optimal conditions for cell treatment and infection. Two factors that affect virus binding and infection efficiency were studied: the use of an adsorption step, where infection volume was varied; and the concentration of fetal bovine serum (FBS). The adsorption step, with or without FBS, increased the bound virus percentage, whereas it increased bound virus at equilibrium only in FBS-free until 2.5% FBS. In contrast, the addition of 10% FBS decreased the bound virus percentage. The inhibition of MV replication in Vero cells was observed when Cdt was added either before or during cell infection with virus. Its inhibitory concentration against MV replication was 0.1 until 100 microg/ml, respectively. The anti-MV effect of the Cdt was gradually decreased when it was added before or during infection, and little inhibition was observed when Cdt was added 1 h after infection, suggesting that the MV infection was inhibited at the time of the initial events such as at the moment of adsorption and penetration of the viral cycle. In conclusion, Cdt contains anti-MV effects that may be of potential clinical interest.

Hemorrhagic activity of the Duvernoy's gland secretion of the xenodontine colubrid Philodryas patagoniensis from the north-east region of Argentina

Colubrid snakes belonging to Philodryas genus, widespread all over South America, bring about lesions (swelling, ecchymosis, transient bleeding from the bite site punctures), that are similar to those produced by Bothrops species (yarará). In the present work we began the characterization of Philodryas patagoniensis venom. We examined if this venom produces hemorrhagic lesions as those observed in victims bitten by Philodryas olfersii. Hemorrhagic, proteolytic and fibrinogenolytic activities were evaluated, and histological observations in samples of gastrocnemius muscle were carried out. Inhibition studies were carried out in metal chelator (ethylenediaminetetraacetic acid) presence. Our results show a small Minimum Hemorrhagic Dose (MHD=0.035 microg) and a high proteolytic activity (143 U/mg), and prove the capacity of this venom to degrade fibrinogen in vitro rendering it unclottable by thrombin, supporting the presence of proteases, principally metalloproteases, in P. patagoniensis venom that are able to alterate the vascular wall and degrade fibrinogen, being both activities responsible of a high hemorrhagic activity.

Resolution of isoforms of mutalysin II, the metalloproteinase from bushmaster snake venom

Mutalysin II, a zinc endopeptidase possessing direct-acting fibrinolytic activity has been previously purified from bushmaster (Lachesis muta muta) snake venom. We now report a method to isolate two isoforms of natural mutalysin II (mut IIa and mut IIb) using chromatographies on Sephacryl S-200, CM Sepharose CL 6B and Sephadex G-50. The two proteins are monomeric non-glycosylated proteinases with similar molecular masses of 23 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Tryptic peptide mapping of the two native enzymes suggested a large degree of structural similarity. Both isoforms showed high similarity in all enzymatic properties using fibrinogen, fibrin and dimethylcasein as substrates. Thus, the specific fibrinolytic activity was estimated as 12+/-1.04 and 11.5+/-1.02 U/microg for mut IIa and mut IIb, respectively. The antigenic cross-reactivity of both isoforms was examined using rabbit hyperimmune serum or immunoglobulin G anti-mut IIa assays on immunodiffusion microscope slides, indirect enzyme-linked immunoabsorbent assay and western blots. From these experiments it was concluded that the two metalloproteinases mut IIa and mut IIb share identical antigenic structures. Since the stability of mutalysin II is dependent upon the presence of zinc, we examined the EDTA sensitivity of the isoforms of mutalysin II. Thus, the IC(50) values (concentration of EDTA to produce 50% inhibition of dimethylcasein hydrolysis) for mut IIa is 180 microM and 165 microM for mut IIb.

A novel prothrombin activator from the venom of Micropechis ikaheka: isolation and characterization

A novel prothrombin activator, Mikarin, has been isolated from Micropechis ikaheka venom. It is a single polypeptide chain metalloproteinase with the apparent molecular weight of 47kDa. Mikarin exhibits Ca(2+)-independent prothrombin activation, but no effects on other blood coagulation factors, such as factor X and fibrinogen. Mikarin is the first member of group I prothrombin activators from elapid venom. Like other high-molecular-weight snake venom proteinases, it has three structural domains, metalloproteinase and disintegrin-like and Cys-rich domains, and belongs to the P-III class of snake venom metalloproteinases. The N-terminal of Mikarin exhibits 76% sequence identity with Cobrin, a metalloproteinase identified from Naja naja venom, but very lower identities were found when compared with those from viperid and crotalid venom. In addition, the presence of disintegrin-like and Cys-rich domains in snake venom metalloproteinases with diverse biological activities suggests that these domains may be important for their function.

Ontogenetic variation of metalloproteinases and plasma coagulant activity in venoms of wild Bothrops atrox specimens from Amazonian rain forest

A comparative study of venoms from juvenile, sub-adult and adult wild Bothrops atrox specimens captured in Manaus region (Brazil) was performed. All venoms tested had acidic pH (5.5) and the human plasma coagulant activity was higher in venoms from juvenile and sub-adult specimens than in adults. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the most intense bands in adult venoms corresponded to polypeptides of 23 and 50kDa. The 23kDa protein was not detected in juvenile venoms. The 23 and 50kDa proteins were purified by two steps of reversed phase-HPLC followed by size exclusion HPLC. Partial amino acid sequence of the 23kDa protein showed homology to metalloproteinases from other snake venoms. Electrospray ionization mass spectrometric analysis (ESI-MS) showed that the 23kDa band contained at least three isoforms of 23030, 23300 and 23645Da. The 50kDa polypeptide was N-terminally blocked for Edman degradation and presented molecular masses ranging from 46.8 to 49.4kDa by ESI-MS. Both proteins were detected by anti-mutalysin II antibodies in immunoblotting assay indicating that they belong to the metalloproteinase family. Immunoblotting analysis also showed that the 23kDa band increased in intensity from juvenile to adult specimens.SDS-PAGE analysis of juvenile and adult venoms following autoproteolysis in pH 7.4 suggested that endogenous venom metalloproteinases can digest the 50kDa metalloproteinase, originating a new protein band of 27kDa. It was also demonstrated in juvenile venoms that the 23kDa band was not the result of proteolytic processing of the 50kDa metalloproteinase.