Purification and partial characterization of a thrombin-like/gyroxin enzyme from bushmaster (Lachesis muta rhombeata) venom

The Colombian bushmasters Lachesis acrochorda (García, 1896) and Lachesis muta (Linnaeus, 1766): Snake species, venoms, envenomation, and its management

In Colombia, there are two species of bushmaster snakes, Lachesis acrochorda, which is distributed mainly in the west of the country (in the Choco region), and Lachesis muta in the southeast (in the Amazon and Orinoquia region), whose presence has been reduced due to the destruction of their habitats. Captive maintenance is challenging, making it difficult to obtain their venom for study and antivenom manufacturing. They are the largest vipers in the world. The occurrence of human envenomation is quite rare, but when it occurs, it is associated with high mortality. Bushmaster venom is necrotizing, hemorrhagic, myotoxic, hemolytic, and cardiovascular depressant. Due to the presence of bradycardia, hypotension, emesis, and diarrhea in some patients (Lachesis syndrome), the possibility of a vagal or cholinergic effect is raised. The treatment of envenomation is hindered by the scarcity of antivenom and the need to use high doses. A review of the most relevant biological and medical aspects of bushmaster snakes is presented, mainly for those occurring in Colombia, to facilitate their recognition and raise awareness about the need for special attention to improve their conservation and advance scientific knowledge, in particular, about their venom.

Purification and Characterization of a Novel Factor of Crotoxin Inter-CRO (V-1), a New Phospholipase A2 Isoform from Crotalus durissus collilineatus Snake Venom Using an In Vitro Neuromuscular Preparation

The fractionation of Crotalus durissus collilineatus whole venom through an HPLC chromatographic method enabled the purification of a new V-1 neurotoxin. Inter-CRO (V-1) presents similarity in its primary structure to crotoxin B (CB), suggesting another isoform of this toxin. The aim of this study was to compare V-1 to the crotoxin complex (CA/CB) and CB to elucidate aspects related to its functionality. The homogeneity of the purified protein was confirmed with a molecular mass of 1425.45 Da, further verified by mass spectrometry. The sequence of the protein showed high similarity to other viperid snake venom PLA2 proteins. The results of this study report that V-1 is an uncharacterized novel toxin with different biological activities from CB. V-1 maintained catalytic activity but presented neurotoxic activity as observed by the 2.5-fold increase in twitch tension record compared to control values on isolated muscle cells.

Action of Varespladib (LY-315920), a Phospholipase A2 Inhibitor, on the Enzymatic, Coagulant and Haemorrhagic Activities of Lachesis muta rhombeata (South-American Bushmaster) Venom

Varespladib (VPL) was primarily developed to treat inflammatory disturbances associated with high levels of serum phospholipase A₂ (PLA₂). VPL has also demonstrated to be a potential antivenom support agent to prevent PLA₂-dependent effects produced by snake venoms. In this study, we examined the action of VPL on the coagulant, haemorrhagic and enzymatic activities of Lachesis muta rhombeata (South-American bushmaster) venom. Conventional colorimetric enzymatic assays were performed for PLA₂, caseinolytic and esterasic activities; in vitro coagulant activities for prothrombin time (PT) and activated partial thromboplastin time (aPTT) were performed in rat citrated plasma through a quick timer coagulometer, whereas the dimensions of haemorrhagic haloes obtained after i.d. injections of venom in Wistar rats were determined using ImageJ software. Venom (1 mg/ml) exhibited accentuated enzymatic activities for proteases and PLA₂in vitro, with VPL abolishing the PLA₂ activity from 0.01 mM; VPL did not affect caseinolytic and esterasic activities at any tested concentrations (0.001–1 mM). In rat citrated plasma in vitro, VPL (1 mM) alone efficiently prevented the venom (1 mg/ml)-induced procoagulant disorder associated to extrinsic (PT) pathway, whereas its association with a commercial antivenom successfully prevented changes in both intrinsic (aPTT) and extrinsic (PT) pathways; commercial antivenom by itself failed to avoid the procoagulant disorders by this venom. Venom (0.5 mg/kg)-induced hemorrhagic activity was slightly reduced by VPL (1 mM) alone or combined with antivenom (antivenom:venom ratio 1:3 ‘v/w’) in rats, with antivenom alone producing no protective action on this parameter. In conclusion, VPL does not inhibit other major enzymatic groups of L. m. rhombeata venom, with its high PLA₂ antagonize activity efficaciously preventing the venom-induced coagulation disturbances.

The Search for Natural and Synthetic Inhibitors That Would Complement Antivenoms as Therapeutics for Snakebite Envenoming

A global strategy, under the coordination of the World Health Organization, is being unfolded to reduce the impact of snakebite envenoming. One of the pillars of this strategy is to ensure safe and effective treatments. The mainstay in the therapy of snakebite envenoming is the administration of animal-derived antivenoms. In addition, new therapeutic options are being explored, including recombinant antibodies and natural and synthetic toxin inhibitors. In this review, snake venom toxins are classified in terms of their abundance and toxicity, and priority actions are being proposed in the search for snake venom metalloproteinase (SVMP), phospholipase A2 (PLA2), three-finger toxin (3FTx), and serine proteinase (SVSP) inhibitors. Natural inhibitors include compounds isolated from plants, animal sera, and mast cells, whereas synthetic inhibitors comprise a wide range of molecules of a variable chemical nature. Some of the most promising inhibitors, especially SVMP and PLA2 inhibitors, have been developed for other diseases and are being repurposed for snakebite envenoming. In addition, the search for drugs aimed at controlling endogenous processes generated in the course of envenoming is being pursued. The present review summarizes some of the most promising developments in this field and discusses issues that need to be considered for the effective translation of this knowledge to improve therapies for tackling snakebite envenoming.

Small Angle X-ray Scattering, Molecular Modeling, and Chemometric Studies from a Thrombin-Like (Lmr-47) Enzyme of Lachesis m. rhombeata Venom

INTRODUCTION

Snakebite envenomation is considered a neglected tropical disease, and SVTLEs critical elements are involved in serious coagulopathies that occur on envenoming. Although some enzymes of this group have been structurally investigated, it is essential to characterize other proteins to better understand their unique properties such as the Lachesis muta rhombeata 47 kDa (Lmr-47) venom serine protease.

METHODS

The structure of Lmr-47 was studied in solution, using SAXS, DLS, CD, and in silico by homology modeling. Molecular docking experiments simulated 21 competitive inhibitors.

RESULTS

At pH 8.0, Lmr-47 has an Rg of 34.5 ± 0.6 Å, Dmax of 130 Å, and SR of 50 Å, according to DLS data. Kratky plot analysis indicates a rigid shape at pH 8.0. Conversely, the pH variation does not change the center of mass's intrinsic fluorescence, possibly indicating the absence of fluorescent amino acids in the regions affected by pH variation. CD experiments show a substantially random coiled secondary structure not affected by pH. The low-resolution model of Lmr-47 presented a prolate elongated shape at pH 8.0. Using the 3D structure obtained by molecular modeling, docking experiments identified five good and three suitable competitive inhibitors.

CONCLUSION

Together, our work provided insights into the structure of the Lmr-47 and identified inhibitors that may enhance our understanding of thrombin-like family proteins.

Neutralization of hemostatic disorders induced by Lachesis muta venom using Brazilian antivenoms

We characterized the hemorrhagic, coagulant and defibrinogenant activities of Lachesis muta venom and evaluated the capacity of the Brazilian antivenoms in neutralizing these activities. The hemorrhagic activity of L. muta venom was similarly neutralized by Bothrops, Bothrops-Lachesis and Bothrops-Crotalus antivenoms. The coagulant and defibrinogenant activities were better neutralized by the Bothrops-Lachesis antivenom. Bothrops-Crotalus antivenom also neutralized these activities, indicating that it can be an alternative to treat Lachesis envenomations when Bothrops-Lachesis antivenom is unavailable.

A brief review on the natural history, venomics and the medical importance of bushmaster (Lachesis) pit viper snakes

Snakes of the genus Lachesis, commonly known as bushmasters, are the largest venomous snakes in the Americas. Because these snakes have their habitats in areas of remote forests they are difficult to find, and consequently there are few studies of Lachesis taxa in their natural ecosystems. Bushmasters are distributed in tropical forest areas of South and Central America. In Brazil they can be found in the Amazon Rainforest and the Atlantic Forest. Despite the low incidence of cases, laquetic envenoming causes severe permanent sequelae due to the high amount of inoculated venom. These accidents are characterized by local pain, hemorrhage and myonecrosis that can be confused with bothropic envenomings. However, victims of Lachesis bites develop symptoms characteristic of Lachesis envenoming, known as vagal syndrome. An important message of this bibliographic synthesis exercise is that, despite having the proteomic profiles of all the taxa of the genus available, very few structure-function correlation studies have been carried out. Therefore the motivation for this review was to fill a gap in the literature on the genus Lachesis, about which there is no recent review. Here we discuss data scattered in a number of original articles published in specialized journals, spanning the evolutionary history and extant phylogeographic distribution of the bushmasters, their venom composition and diet, as well as the pathophysiology of their bites to humans and the biological activities and possible biotechnological applicability of their venom toxins.

Subproteome of Lachesis muta rhombeata venom and preliminary studies on LmrSP-4, a novel snake venom serine proteinase

Background:

Lachesis muta rhombeata is one of the venomous snakes of medical importance in Brazil whose envenoming is characterized by local and systemic effects which may produce even shock and death. Its venom is mainly comprised of serine and metalloproteinases, phospholipases A₂ and bradykinin-potentiating peptides. Based on a previously reported fractionation of L. m. rhombeata venom (LmrV), we decided to perform a subproteome analysis of its major fraction and investigated a novel component present in this venom.

Methods:

LmrV was fractionated through molecular exclusion chromatography and the main fraction (S5) was submitted to fibrinogenolytic activity assay and fractionated by reversed-phase chromatography. The N-terminal sequences of the subfractions eluted from reversed-phase chromatography were determined by automated Edman degradation. Enzyme activity of LmrSP-4 was evaluated upon chromogenic substrates for thrombin (S-2238), plasma kallikrein (S-2302), plasmin and streptokinase-activated plasminogen (S-2251) and Factor Xa (S-2222) and upon fibrinogen. All assays were carried out in the presence or absence of possible inhibitors. The fluorescence resonance energy transfer substrate Abz-KLRSSKQ-EDDnp was used to determine the optimal conditions for LmrSP-4 activity. Molecular mass of LmrSP-4 was determined by MALDI-TOF and digested peptides after trypsin and Glu-C treatments were analyzed by high resolution MS/MS using different fragmentation modes.

Results:

Fraction S5 showed strong proteolytic activity upon fibrinogen. Its fractionation by reversed-phase chromatography gave rise to 6 main fractions (S5C1-S5C6). S5C1-S5C5 fractions correspond to serine proteinases whereas S5C6 represents a C-type lectin. S5C4 (named LmrSP-4) had its N-terminal determined by Edman degradation up to the 53^rd amino acid residue and was chosen for characterization studies. LmrSP-4 is a fibrinogenolytic serine proteinase with high activity against S-2302, being inhibited by PMSF and benzamidine, but not by 1,10-phenantroline. In addition, this enzyme exhibited maximum activity within the pH range from neutral to basic and between 40 and 50 °C. About 68% of the LmrSP-4 primary structure was covered, and its molecular mass is 28,190 Da.

Conclusions:

Novel serine proteinase isoforms and a lectin were identified in LmrV. Additionally, a kallikrein-like serine proteinase that might be useful as molecular tool for investigating bradykinin-involving process was isolated and partially characterized.

Experimental Lachesis muta rhombeata envenomation and effects of soursop (Annona muricata) as natural antivenom

Background

In the Atlantic forest of the North and Northeast regions of Brazil, local population often uses the fruit juice and the aqueous extract of leaves of soursop (Annona muricata L.) to treat Lachesis muta rhombeata envenomation. Envenomation is a relevant health issue in these areas, especially due to its severity and because the production and distribution of antivenom is limited in these regions. The aim of the present study was to evaluate the relevance of the use of soursop leaf extract and its juice against envenomation by Lachesis muta rhombeata.

Methods

We evaluated the biochemical, hematological and hemostatic parameters, the blood pressure, the inflammation process and the lethality induced by Lachesis muta rhombeata snake venom. We also assessed the action of the aqueous extract of leaves (AmL) and juice (AmJ) from A. muricata on the animal organism injected with L. m. rhombeata venom (LmrV) in the laboratory environment.

Results

LmrV induced a decrease of total protein, albumin and glucose; and increase of creatine kinase, aspartate aminotransferase, and urea concentrations. It provoked hemoconcentration followed by reduction of hematocrit, an increase in prothrombin time and partial thromboplastin time and a decrease of the blood pressure. LmrV induced the release of interleukin-6, an increase in neutrophils and changes in the serum protein profile, characteristic of the acute inflammatory process. LD₅₀ values were similar for the groups injected with LmrV and treated or untreated with AmJ and AmL. Both treatments play a role on the maintenance of blood glucose, urea and coagulation parameters and exert a protective action against the myotoxicity. However, they seem to worsen the hypotension caused by LmrV.

Conclusion

The treatments with AmJ and AmL present some beneficial actions, but they might intensify some effects of the venom. Therefore, additional studies on A. muricata are necessary to enable its use as natural antivenom for bushmaster snakebite.

Identification of hyaluronidase and phospholipase B in Lachesis muta rhombeata venom

Hyaluronidases contribute to local and systemic damages after envenoming, since they act as spreading factors cleaving the hyaluronan presents in the connective tissues of the victim, facilitating the diffusion of venom components. Although hyaluronidases are ubiquitous in snake venoms, they still have not been detected in transcriptomic analysis of the Lachesis venom gland and neither in the proteome of its venom performed previously. This work purified a hyaluronidase from Lachesis muta rhombeata venom whose molecular mass was estimated by SDS-PAGE to be 60 kDa. The hyaluronidase was more active at pH 6 and 37 °C when salt concentration was kept constant and more active in the presence of 0.15 M monovalent ions when the pH was kept at 6. Venom was fractionated by reversed-phase liquid chromatography (RPLC). Edman sequencing after RPLC failed to detect hyaluronidase, but identified a new serine proteinase isoform. The hyaluronidase was identified by mass spectrometry analysis of the protein bands in SDS-PAGE. Additionally, phospholipase B was identified for the first time in Lachesis genus venom. The discovery of new bioactive molecules might contribute to the design of novel drugs and biotechnology products as well as to development of more effective treatments against the envenoming.

Rapid purification and procoagulant and platelet aggregating activities of Rhombeobin: a thrombin-like/gyroxin-like enzyme from Lachesis muta rhombeata snake venom

We report a rapid purification method using one-step chromatography of SVSP Rhombeobin (LMR-47) from Lachesis muta rhombeata venom and its procoagulant activities and effects on platelet aggregation. The venom was fractionated by a single chromatographic step in RP-HPLC on a C8 Discovery BIO Wide Pore, showing high degree of molecular homogeneity with molecular mass of 47035.49 Da. Rhombeobin showed amidolytic activity upon BA ρ NA, with a broad optimum pH (7-10) and was stable in solution up to 60°C. The amidolytic activity was inhibited by serine proteinase inhibitors and reducing agents, but not chelating agents. Rhombeobin showed high coagulant activity on mice plasma and bovine fibrinogen. The deduced amino acid sequence of Rhombeobin showed homology with other SVSPs, especially with LM-TL (L. m. muta) and Gyroxin (C. d. terrificus). Rhombeobin acts, in vitro, as a strong procoagulant enzyme on mice citrated plasma, shortening the APTT and PT tests in adose-dependent manner. The protein showed, "ex vivo", a strong defibrinogenating effect with 1 µg/animal. Lower doses activated the intrinsic and extrinsic coagulation pathways and impaired the platelet aggregation induced by ADP. Thus, this is the first report of a venom component that produces a venom-induced consumptive coagulopathy (VICC).

Biochemical and biological characterization of two serine proteinases from Colombian Crotalus durissus cumanensis snake venom

Two clotting serine proteinases, named Cdc SI and Cdc SII, were isolated and characterized for the first time from Colombian Crotalus durissus cumanensis snake venom. The enzymes were purified using two chromatographic steps: molecular exclusion on Sephacryl S-200 and RP-HPLC on C8 Column. The molecular masses of the proteins, determined by MALDI-TOF mass spectrometry, were 28,561.4 and 28,799.2 Da for Cdc SI and Cdc SII, respectively. The aim of the present study was to evaluate enzymatic, coagulant and toxic properties of the two enzymes. The serine proteinases hydrolyzed specific chromogenic substrate (BaPNA) and exhibited a Michaelis-Menten behavior. Cdc SI had V(max) of 0.038 ± 0.003 nmol/min and K(M) of 0.034 ± 0.017 mM, while Cdc SII displayed values of V(max) of 0.267 ± 0.011 nmol/min and K(M) of 0.145 ± 0.023 mM. N-terminal sequences were VIGGDEXNIN and VIGGDICNINEHNFLVALYE for Cdc SI and Cdc SII, respectively. Molecular masses, N-terminal sequences, inhibition assays, and enzymatic profile suggest that Cdc SI and Cdc SII belong to the family of snake venom thrombin-like enzymes. These serine proteinases differed in their clotting activity on human plasma, showing a minimum coagulant dose of 25 μg and 0.571 μg for Cdc SI and Cdc SII, respectively. Enzymes also showed coagulant activity on bovine fibrinogen and degraded chain α of this protein. Toxins lack hemorrhagic and myotoxic activities, but are capable to induce defibrin(ogen)ation, moderate edema, and an increase in vascular permeability. These serine proteinases may contribute indirectly to the local hemorrhage induced by metalloproteinases, by causing blood clotting disturbances, and might also contribute to cardiovascular alterations characteristic of patients envenomed by C. d. cumanensis in Colombia.

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

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

BJ-48, a novel thrombin-like enzyme from the Bothrops jararacussu venom with high selectivity for Arg over Lys in P1: Role of N-glycosylation in thermostability and active site accessibility

BJ-48, a serine protease from the venom of Bothrops jararacussu, was purified to homogeneity using affinity chromatography on p-aminobenzamidine-agarose followed by HPLC gel filtration. BJ-48 presented 52kDa by SDS-PAGE analysis and 48,036Da by electron spray mass spectrometry. The enzyme was shown to be highly glycosylated with 42% of N-linked carbohydrates composed of Fuc(1):GalN(4):GlcN(5):Gal(1):Man(2) and a high content of sialic acid residues (8-12%). BJ-48 had optimal esterase activity at pH 7.5 and displayed maximum catalytic rate at 50 degrees C. Its hydrolytic activity was strongly inhibited by aprotinin and dithiothreitol while N-tosyl-l-phenylalanine chloromethyl ketone, 6-aminocaproic acid, E-64 and soybean trypsin inhibitor (SBTI) were ineffective. The kinetics of BJ-48 with chromogenic substrates revealed an unprecedented selectivity (10(4)-fold) for Arg over Lys in P1. BJ-48 proved to be a thrombin-like enzyme (TLE) with a specific fibrinogen-clotting activity of 73.4NIH units/mg. The TLE rapidly digested human fibrinogen Bbeta chain, but the Aalpha chain was cleaved specifically to release fibrinopeptide A with k(cat)/K(m)=2.1 microM(-1)s(-1). The TLE showed no activity toward other thrombin substrates like protein C, protease-activated receptor-1 or inhibitors such as hirudin and antithrombin. A non-denaturing procedure using PNGase F and neuraminidase followed by hydrophobic interaction chromatography was employed to obtain active BJ-48 forms with variable carbohydrate content. Compared to the native enzyme, total or partially deglycosylated BJ-48 forms presented up to 2-fold reduction in their specific activities upon heating at 55/65 degrees C or treatment with SBTI. These results point out a role for BJ-48 glycosylation in thermostability and controlling the access of some canonical protein inhibitors to the active site.

Biochemical and molecular modeling analysis of the ability of two p-aminobenzamidine-based sorbents to selectively purify serine proteases (fibrinogenases) from snake venoms

Snake venoms contain several trypsin-like enzymes with equivalent physicochemical characteristics and similar inhibition profiles. These are rather difficult to separate by classical purification procedures and therefore constitute a good model for affinity chromatography analysis. Some of these trypsin homologues present fibrinogenase activity, mimicking one or more features of the central mammalian coagulation enzyme, thrombin. It was previously demonstrated that a number of amidine derivatives are able to interact specifically with some of these serine proteases. To understand the enzyme-sorbent interactions we have investigated the ability of two commercially available benzamidine affinity matrices to purify thrombin-like serine proteases (TLSP) with similar biological properties from two snake venoms (Bothrops jararacussu and Lachesis muta rhombeata). Curiously, each sorbent retained a single but distinct TLSP from each venom with high yield. Molecular modeling analysis suggested that hydrophobic interactions within a specific region on the surface of these enzymes could be generated to explain this exquisite specificity. In addition, it was demonstrated that a specific tandem alignment of the two benzamidine sorbents enables the purification of three other enzymes from B. jararacussu venom.

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

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

Biological and Structural Characterization of a New PLA2 from the Crotalus durissus collilineatus Venom

In the present article we report on the biological characterization and amino acid sequence of a new basic Phospholipases A2 (PLA2) isolated from the Crotalus durissus collilineatus venom (Cdcolli F6), which showed the presence of 122 amino acid residues with a pI value of 8.3, molecular mass of 14 kDa and revealed an amino acid sequence identity of 80% with crotalic PLA2s such as Mojave B, Cdt F15, and CROATOX. This homology, however, dropped to 50% if compared to other sources of PLA2s such as from the Bothrops snake venom. Also, this PLA2 induced myonecrosis, although this effect was lower than that of BthTx-I or whole crotoxin and it was able to induce a strong blockage effect on the chick biventer neuromuscular preparation, independently of the presence of the acid subunid (crotapotin). The neurotoxic effect was strongly reduced by pre-incubation with heparin or with anhydrous acetic acid and p-BPB showed a similar reduction. The p-BPB did not reduce significantly the myotoxic activity induced by the PLA2, but the anhydrous acetic acid treatment and the pre-incubation of PLA2 with heparin reduced significantly its effects. This protein showed a strong antimicrobial activity against Xanthomonas axonopodis passiforae (Gram-negative), which was drastically reduced by incubation of this PLA2 with p-BPB, but this effect was marginally reduced after treatment with anhydrous acetic acid. Our findings here allow to speculate that basic amino acid residues on the C-terminal and molecular regions near catalytic site regions such as Calcium binding loop or beta-wing region may be involved in the binding of this PLA2 to the molecular receptor to induce the neurotoxic effect. The bactericidal effect, however, was completely dependent on the enzymatic activity of this protein.

S1 subsite in snake venom thrombin-like enzymes: can S1 subsite lipophilicity be used to sort binding affinities of trypsin-like enzymes to small-molecule inhibitors?

Thrombin-like enzymes isolated from snake venoms comprise a group of serine proteinases responsible for many important coagulation disorders in the envenomed victims. Besides, these proteinases have great biotechnological interest as antithrombotic agents and as diagnostic tools. However, in spite of the recent overflow of snake venom thrombin-like enzymes (SVTLEs) on protein sequence databases, there is a lack of three-dimensional (3D) structural information on this family. Without such 3D structures available many aspects of the biological function and biochemical properties of these enzymes still remain obscure. Therefore, we have gone through a series of computational techniques, which enabled us to identify the set of residues involved in molecular recognition of inhibitors bound to the S1 subsite of snake venom thrombin-like enzymes (SVTLEs) and ultimately conclude that nonpolar (van der Waals) intermolecular interactions and ligand's hydrophobicity are the most important factors affecting binding affinities to the S1 subsite of a SVTLE isolated from the venom of Lachesis muta muta (Lmm-TLE). Consequently, we have proposed that S1 subsite lipophilicity may be used to sort binding affinities of trypsin-like enzymes to small molecules by showing that the inhibitory potency of several S1-directed compounds follows subsite lipophilicity among Lmm-TLE and other three homologous proteases. Noteworthy, in the course of our analyses we determined that thrombin's S1 subsite should, in fact, be considered less lipophilic than that of trypsin if we account for the presence of the sodium-controlled water channel communicating with the S1 subsite in the coagulant enzyme.

Leishmania amazonensis: early proteinase activities during promastigote-amastigote differentiation in vitro

Leishmania proteinase activity is known as parasite differentiation marker, and has been considered relevant for leishmanial survival and virulence. These properties suggest that Leishmania proteinases can be promising targets for development of anti-leishmania drugs. Here, we analyze the activities of four proteinases during the early phase of the Leishmania amazonensis promastigotes differentiation into amastigotes induced by heat shock. We have examined activities of cysteine-, metallo-, serine-, and aspartic-proteinase by hydrolysis of specific chromogenic substrates at pH 5.0 and at the optimal pH for each enzyme. Our results show that metallo-, serine-, and aspartic-proteinases activities were down-regulated during the shock-induced transformation of promastigotes into amastigotes. In contrast, cysteine-proteinase activity increased concomitantly with the promastigote differentiation. Immunocytochemical localization using two anti-cysteine-proteinase monospecific rabbit antibodies detected the enzyme in several cell compartments of both parasite stages. Our results show different proteinase activity modulation and expression during the early phases of the shock-induced parasite transformation.

Leishmania (Leishmania) amazonensis: purification and characterization of a promastigote serine protease

Pathogenic protozoan proteases play crucial roles in the host-parasite interaction, and its characterization contributes to the understanding of protozoan disease mechanisms. A Leishmania amazonensis promastigote protease was purified 36-fold, using aprotinin-agarose affinity chromatography and gel filtration high performance liquid chromatography, yielding a total recovery of 49%. The molecular mass of active enzyme obtained from native gel filtration HPLC and SDS-PAGE under conditions of reduction and non-reduction was 68 kDa, suggesting that the enzyme may exist as a monomer. The protease isoelectric point (pI) was around 4.45 and, as demonstrated by deglycosylation assay, it did not have any carbohydrate content. The optimal pH and temperature of the enzyme were 8.0 and 28 degrees C, respectively, determined using alpha-N-rho-tosyl-L-arginyl-methyl ester (L-TAME) as substrate. Assays of thermal stability indicated that 50% of the enzymatic activity was preserved after 4 min of pre-treatment at 42 degrees C and after 24 h of pre-treatment at 37 degrees C, both in the absence of substrate. Hemoglobin, bovine serum albumin (BSA), ovalbumin, and both gelatin and peptide substrates containing arginine in ester bound were hydrolyzed by 68 kDa protease. The insulin beta-chain was also hydrolyzed by the protease, and four peptidic bonds (L11-V12, E13-A14, L15-Y16, and Y16-L17) were susceptible to the 68-kDa protease action. Inhibition studies suggested that the enzyme belonged to a serine protease class inhibited by calcium ions and activated by manganese ions. These findings demonstrate that the L. amazonensis 68-kDa serine protease differs from those of other protozoan parasites.

Purification, characterization and crystallization of Jararacussin-I, a fibrinogen-clotting enzyme isolated from the venom of Bothrops jararacussu

A fibrinogen-clotting enzyme, Jararacussin-I, was purified from the venom of Bothrops jararacussu by a combination of ion exchange chromatography using Resource 15S resin and affinity chromatography using Benzamidine Sepharose 6B resin. Jararacussin-I displays a molecular mass of 28 kDa as estimated by sodium dodecyl sulphate-PAGE and possesses an isoelectric point of 5.0. The coagulant specific activity of the enzyme was determined to be 45.8 NIHU/mg using bovine fibrinogen as the substrate and the esterase specific activity was determined to be 258.7 U/mg. The protease inhibitors, benzamidine and DTT inhibited the esterase specific activity by 72.4 and 69.7%, respectively. The optimal temperature and pH for the degradation of both chains of fibrinogen and esterase specific activity were determined to be 37 degrees C and 7.4-8.0, respectively. The enzyme was inactivated at both 4 and 75 degrees C. Single crystals of Jararacussin-I were obtained and complete three-dimensional X-ray diffraction data was collected at the Brazilian National Synchrotron Source (LNLS) to a resolution of 2.4A.

Purification and characterization of a prothrombin-activating protease from Nephila clavata

We report upon the purification and characterization of a novel prothrombin-activating enzyme from the body fluid (total homogenates of isolated digestive tract without eggs, spinnerets and silk glands) of the spider, Nephila clavata by a combination of acetone fractionation, ion exchange, and Soybean trypsin inhibitor-Sepharose chromatography. Analysis of the purified enzyme with SDS-PAGE and gel filtration revealed a single polypeptide chain with an apparent molecular weight of 24kDa. The proteolytic activity of the enzyme was stable up to 50 degrees C, however, it became unstable over 55 degrees C. The enzyme had an optimum pH of 8, and Ca(2+) was not required for the enzyme activity. According to inhibition profiles obtained with several serine protease inhibitors such as PMSF and benzamidine, the purified protease is a member of the serine proteases. Bz-Ile-Glu(gamma-OR)- Gly-Arg-pNA and Z-Arg-Gly-Arg-pNA which are known as substrates for factor Xa, were hydrolyzed favorably by the enzyme. And the Nephila protease could produce thrombin from prothrombin at nM range, and form the turbid ring using fibrinogen-agarose plate. The results obtained confirmed that the purified protease is a potent prothrombin-activating activity belonging to the family of serine protease.

Structural features of a snake venom thrombin-like enzyme: thrombin and trypsin on a single catalytic platform?

The Lachesis muta thrombin-like enzyme (LM-TL) is a single chain serine protease that shares 38% sequence identity with the serine protease domain of thrombin and also displays similar fibrinogen-clotting activity. In addition, the 228 amino acid residue LM-TL is 52% identical to trypsin, and cleaves chromogenic substrates with similar specificity. Herein we report a three-dimensional (3D) model validated experimentally for LM-TL based on these two homologous proteins of known 3D structure. Spatial modeling of LM-TL reveals a serine protease with a chymotrypsin fold presenting a hydrophobic pocket on its surface, involved in substrate recognition, and an important 90's loop, involved in restricting the LM-TL catalytic site cleft. Docking analysis showed that LM-TL would not form a stable complex with basic pancreatic trypsin inhibitor and wild-type ecotin since its 90's loop would restrict the access to the catalytic site. LM-TL formed acceptable interactions with fibrinopeptide A and a variant of ecotin; ecotin-TSRR/R in which both the primary and secondary binding sites are mutated Val81Thr, Thr83Ser, Met84Arg, Met85Arg and Asp70Arg. Furthermore, analysis of the primary structures of LM-TL and of the seven snake venom thrombin-like enzymes (SVTLEs) family reveals a subgroup formed by LM-TL, crotalase, and bilineobin, both closely related to thrombin. Therefore, LM-TL provides an initial point to compare SVTLEs with their counterparts, e.g. the mammalian serine proteases, and a basis for the localization of important residues within the little known SVTLEs family.

Gyroxin fails to modify in vitro release of labelled dopamine and acetylcholine from rat and mouse striatal tissue

Gyroxin fails to modify in vitro release of labelled dopamine and acetylcholine from rat and mouse striatal tissue. Gyroxin is a thrombin-like peptide with amidasic, esterasic and fibrinogenolitic activities, found in the venom of snakes like Lachesis muta muta and Crotalus durissus terrificus. Intravenous injections of small doses of gyroxin induce a typical barrel rotation behaviour that has been thought to be a neurotoxic effect. The aim of this study was to determine whether gyroxin-induced barrel rotation behaviour involves changes in neurotransmitter release. Gyroxin was isolated from crude venoms by gel filtration and affinity chromatography. Its properties were determined by assaying esterasic, amidasic and fibrinogenolitic enzymatic activities and tested for barrel rotation behaviour. Neurotransmitter release tests employed rat and mouse superfused brain striatal chopped tissue preloaded with [(3)H]-dopamine, [(3)H]-acetylcholine or in a double labelling procedure. They were stimulated by 20mM K(+) in control conditions or in the presence of several concentrations of toxins. Crotoxin and crotamine were used as positive controls. Gyroxins failed at modifying both basal and stimulated neurotransmitter releases, suggesting a lack of direct neurotoxic effect. We therefore suggest that gyroxin may not be a neurotoxin but rather, induces this behavioural syndrome by other means possibly related to haemodynamic disturbance. The possible role of vasopressin is discussed.

Purification and characterization of calobin II, a second type of thrombin-like enzyme from Agkistrodon caliginosus (Korean viper)

In our previous report, we purified and cloned the gene of a thrombin-like enzyme, calobin, from the venom of Agkistrodon caliginosus (Hahn, B.S., Yang, K.Y., Park, E.M., Chang, I.M., Kim, Y. S., 1996. Purification and molecular cloning of calobin, a thrombin-like enzyme from Agkistrodon caliginosus (Korean viper). J. Biochem. 119, 835-843.). During the purification of calobin, a second type of thrombin-like protease was found and it was purified using Affi-Gel Blue and Mono-S cation-exchange chromatography. It was identified as a serine protease with a molecular weight of 41, 000 on SDS-PAGE and its isoelectric point was determined to be 7.4 by isoelectric focusing. It showed little azocaseinolytic and fibrinolytic activity. However, this enzyme acted on fibrinogen to form fibrin with a specific activity of 7,587 NIH equivalent units and also exhibited arginine esterase activity. Amino acid sequencing of the N-terminal region established a primary structure composed of Val-Ile-Gly-Gly-Asp-Glu-Cys-Asn-Ile-Asn-Glu-His-Arg-Phe-Leu-Val-Ala-X -Tyr. This sequence was entirely consistent with that of calobin and showed a high homology with other thrombin-like enzymes, such as ancrod, batroxobin and gyroxin. Based on the biochemical properties such as molecular weight and isoelectric point, we can demonstrate a second thrombin-like protein showing a high potent clotting activity from the venom of Korean viper.

Two related thrombin-like enzymes present in Bothrops atrox venom

This article describes the presence of two new forms of a thrombin-like enzyme, both with apparent molecular masses of 38 kDa, in Bothrops atrox venom. Both share the ability to cleave fibrinogen into fibrin and to digest casein. Both present identical K(m) on the substrate BApNA. Their N-terminal amino acid sequences are identical for 26 residues, sharing 80% homology with batroxobin and flavoxobin. Two groups of monoclonal antibodies (mAbs) raised against the purified enzyme forms recognized different epitopes of the putative corresponding enzymes present in B. atrox crude venom. On Western blotting analysis of B. atrox crude venom, mAbs 5DB2C8, 5AA10 and 5CF11, but not mAbs 6CC5 and 6AD2-G5, revealed two or more protein bands ranging from 25 to 38 kDa. By immunoprecipitation assays, the 6AD2-G5 mAb was able to precipitate protein bands of 36-38 kDa from B. atrox, B. leucurus, B. pradoi, B. moojeni, B. jararaca and B. neuwiedii crude venoms. Fibrinogen-clotting activity was inhibited when the same venom specimens were pre-incubated with mAb 6AD2-G5, except for B. jararaca and B. neuwiedii.

Extracellular serine-proteinases isolated from Streptomyces alboniger: partial characterization and effect of aprotinin on cellular structure

Streptomyces alboniger ATCC 12461 grown in brain heart infusion (BHI) medium produced two extracellular serine-proteinases, denoted SP I and SP II, which were purified by ammonium sulfate precipitation and aprotinin-agarose affinity chromatography. SP I was purified 88,9-fold and SP II 66,7- fold, with 33.4% and 10.4% yield, respectively. The optimum pH for the proteinases activity, using a-N-p-tosyl-L-arginine-methyl ester (TAME) as substrate, was 9-10 and the optimum temperature was 37 degrees C. The proteolytic activity of SP I and SP II was inhibited by aprotinin and SP I was partially inhibited by leupeptin, both serine-proteinase inhibitors. S. alboniger growth in BHI-liquid medium decreased when 5 mg/ml, 10 mg/ml of aprotinin was used, being completely inhibited with 20 mg/ml and 40 mg/ml. At the ultrastructural level, aprotinin-treated S. alboniger cells showed swelling of the bacterial body and condensation of the genetic material, probably related to the inhibition of its growth.

Purification and partial characterization of an extracellular serine-proteinase of Streptomyces cyaneus isolated from Brazilian cerrado soil

Streptomyces cyaneus, a micro-organism isolated from Brazilian cerrado soil, produces an extracellular proteinase (SCP), which was purified 22-fold to homogeneity from culture supernatant fluid, using a single aprotinin-agarose affinity chromatography step. It is produced at a level corresponding to approximately 15% of total protein, but its physiological function has yet to be determined. The molecular mass of this S. cyaneus proteinase was estimated to be 120 kDa by gel filtration high performance liquid chromatography, and it migrates by SDS-PAGE as a single band of 30 kDa. It was optimally active at 25 degrees C and pH 9.0, and was fully inhibited by the serine-proteinase inhibitors PMSF and TPCK. A Km value of 1. 86 x 10-5 mmol l-1, and Vmax of 2.0 x 10-2 mmol l-1 (Abs247 nm microg-1 min-1), were calculated for alpha-N-p-tosyl-L-arginine-methyl ester (TAME) as substrate.

Purification and characterization of two fibrinogen-clotting enzymes from five-pace snake (Agkistrodon acutus) venom

From the snake venom of Agkistrodon acutus, two proteases, acuthrombin-A and acuthrombin-C, were isolated and purified to homogeneity. They can cleave the human fibrinogen to release the fibrinopeptide A and fibrinopeptide B with specific activity of 120 and 370 NIH units/mg, respectively; the fibrinogen-clotting activity can be inhibited distinctly by PMSF or DFP or EDTA, but not by heparin. The two proteases show also arginine-esterase activity hydrolyzing some synthetic substrates such as TAME and BAEE. Additionally, they are glycoproteins with an average content of 2.4% (acuthrombin-A) and 2.1% (acuthrombin-C) neutral carbohydrates, respectively. Acuthrombin-A has a MW of 13,900 as estimated by SDS-PAGE under reduced or nonreduced conditions and 28,000 as determined by gel filtration. For acuthrombin-C, there were two protein bands corresponding to MW of 13,900 and 14,800 on SDS-PAGE with different darkness under reduced or nonreduced conditions, while its MW was estimated to be 69,000 by gel filtration. The isoelectric points were 7.5 for acuthrombin-A and 5.0 for acuthrombin-C by isoelectric focusing. Neither acuthrombin-A nor acuthrombin-C has haemorrhagic or lethal activity. Acuthrombin-A has also a small amount of activity to activate the Factor XIII.

Isolation, properties and N-terminal amino acid sequence of a factor V activator from Vipera lebetina (Levantine viper) snake venom

A factor V activator (VLFVA) was separated from Vipera lebetina venom by gel filtration on Sephadex G-100 superfine, followed by chromatography on CM-cellulose and on heparin-agarose. This enzyme (VLFVA) with a molecular mass of 28.4 kDa, as determined by matrix assisted laser desorption ionization time-of-flight mass spectrometry, is a single-chain glycoprotein containing seven residues of neutral sugars, seven residues of hexosamines and three residues of neuraminic acid per molecule. The treatment with N-glycosidase F lowered the molecular mass approximately 6%. The N-terminal sequencing of VLFVA up to the 30th residue evidenced a high homology with Vipera russelli factor V activator RVV-Vgamma (90% identity). Aside from factor V, no other protein substrate for VLFVA has yet been identified. VLFVA hydrolyzes several synthetic arginine ester substrates, such as benzoylarginine ethyl ester (BAEE), tosylarginine methyl ester (TAME) and amide substrates such as Pro-Phe-Arg-MCA. The arginine ester hydrolase activity of the enzyme is markedly lower than that of the crude venom. The ability of VLFVA to activate factor V and its activity to BAEE and TAME were inhibited by the serine proteinase inhibitor, diisopropylfluorophosphate. VLFVA is thermostable protein, heating for 20 min at 70 degrees C does not alter the arginine esterase activity of the enzyme.

Purification, properties, and N-terminal amino acid sequence of a kallikrein-like enzyme from the venom of Lachesis muta rhombeata (Bushmaster)

Pit viper venoms contain multiple proteinases which cause considerable damage in tissues and systemic effects after envenomation. A proteinase, kallikrein-like enzyme, belonging to the serine group must play a very important role on systemic effects. The corresponding enzyme from Lachesis muta rhombeata venom was purified to homogeneity by a combination of isoelectrofocusing fractionation followed by one step of gel filtration HPLC. The enzyme focused with pI 5.0-6.5, it had a molecular mass of 32 kDa by gel filtration HPLC, had edematogenic activity, and induced a hypotensic effect in anesthetized rats. It exhibited strong N-alpha-tosyl-L-Arg methyl esterase (955.38 units/mg) and N-Bz-DL-Arg-pNA amidolytic (233.02 units/mg) activities, hydrolyzed tripeptide nitroanilide derivatives weakly or not at all, and cleaved selectively the A-alpha and B-beta chains of fibrinogen, apparently leaving the Y-chain unaffected. The 30 N-terminal amino acid sequence of the L. m. rhombeata protein showed greatest identity (74% in 26 amino acids) with Crotalus viridis kallikrein-like protein, but significant similarities in sequence were observed with enzymes from other snake venoms and pig pancreatic kallikrein.

Snakebite by the bushmaster (Lachesis muta) in Brazil: case report and review of the literature

The bushmaster (Lachesis muta) of Central and South America, the world's longest pit viper, is capable of injecting a large dose of potent venom when it bites. A 28-year-old man, bitten by a 1.82 m long L. m. muta in Brazil, developed pain and oedema at the bite site, nausea, vomiting, diarrhoea and sweating. There was peripheral neutrophil leucocytosis and evidence of fibrinogen consumption with secondary activation of the fibrinolytic system. Two hours after the bite, eight ampoules of Instituto Butantan Lachesis antivenom was administered, and haemostasis was normal 24 hr later. A review of reports of 20 cases of bites in humans reliably attributed to this snake in Costa Rica, French Guiana, Brazil, Colombia and Venezuela confirms a syndrome of nausea, vomiting, abdominal colic, diarrhoea, sweating, hypotension, bradycardia and shock, possibly autopharmacological or autonomic in origin, not seen in victims of other American crotaline snakes. These, and other symptoms of bushmaster envenoming, are explained by haemorrhagic, coagulant and neurotoxic venom activities. The therapeutic efficacy of non-specific Bothrops/Crotalus polyvalent antivenoms in these cases has been unimpressive. For the treatment of bites by a snake which potentially injects a large dose (> 300 mg dry weight) of venom with a range of life-threatening activities, there is an urgent need to develop more potent specific antivenoms and to treat the dramatic and life-threatening cardiovascular symptoms.

Single-step purification of crotapotin and crotactine from Crotalus durissus terrificus venom using preparative isoelectric focusing

We describe the isolation of crotoxin, a presynaptic B-neurotoxin, as well as its subunits B (crotactine) and A (crotapotin) from lyophilized Crotalus durissus terrificus venom by a single-step preparative isoelectric focusing procedure. From 98 mg of dried venom protein 20.1 mg of crotactine and 13.1 mg of crotapotin were recovered in the first step of focalization and 4.2 mg in a second run. These values correspond to 35.7% of the total venom protein applied. Crotactine separated in the 9.3-7.0 pH range (tubes 1-6) and crotapotin in the 1.8-2.8 pH range (tubes 15-19) and both were homogeneous by SDS-PAGE and N-terminal amino acid analysis. Crotactine, a 12-kDA protein, presented hemolytic and phospholipase A2 activity. Thus, using isoelectric focusing we simultaneously purified both toxins in high yields. This method can be used as an alternative for the purification and characterization of proteins from other snake venoms under conditions in which biological activity is retained.