Fibrinolytic enzyme(s) in western diamondback rattlesnake (Crotalus atrox) venom

Thromboelastography with Platelet Studies (TEG® with PlateletMapping®) After Rattlesnake Envenomation in the Southwestern United States Demonstrates Inhibition of ADP-Induced Platelet Activation As Well As Clot Lysis

INTRODUCTION

Hematologic effects of North American rattlesnake envenomation can include fibrinogenolysis and thrombocytopenia, depending on species, geography, and other variables. During treatment, these effects are routinely monitored through assessment of fibrinogen concentrations and platelet counts. However, these tests provide no information about fibrinolysis or platelet dysfunction, both of which can also occur with venom from some species.

METHODS

This was a retrospective chart review of patients admitted to a quaternary care academic hospital (Banner - University Medical Center Phoenix) in the southwestern United States for treatment of rattlesnake envenomation, over an approximately 1-year period from March 2017 through April 2018. Patients who had thromboelastography with platelet studies (TEG® with PlateletMapping®) during their care were included.

RESULTS

Twelve patients were identified for this study. Four patients exhibited inhibition of ADP-induced platelet activation: one had normal fibrinogen and platelet count, two had concurrent hypofibrinogenemia, and one had concurrent thrombocytopenia. Crotalidae polyvalent immune Fab (ovine) reversed platelet inhibition in the single patient for whom serial thromboelastographs were available. Fibrinolysis was present in seven patients and resolved in the two patients with serial thromboelastographs.

CONCLUSIONS

Inhibition of ADP-induced platelet aggregation and fibrinolysis occurred independent of hypofibrinogenemia and thrombocytopenia, indicating fibrinogen concentration (or protime) and platelet count monitoring alone is insufficient to assess the extent of hematologic toxicity in rattlesnake envenomation. Crotalidae polyvalent immune Fab (ovine) reversed platelet inhibition in one case, suggesting platelet inhibition could also be used in treatment decisions. Fibrinolysis could also be reversed, although the timing to antivenom administration was less clear.

Effects of purified human fibrinogen modified with carbon monoxide and iron on coagulation in rabbits injected with Crotalus atrox venom

While snake venom derived enzymes, such as the thrombin-like activity possessing ancrod, have been used to treat thrombotic disease by defibrinogenating patients, the therapeutic potential of fibrinogenolytic snake venom enzymes, such as those derived from Crotalus atrox, have not been fully explored. However, one of the potential risks of administering fibrinogenolytic enzymes to effect defibrinogenation is hemorrhage secondary to hypofibrinogenemia. The present investigation sought to determine if human fibrinogen modified with carbon monoxide (CO) and iron (Fe) could resist degradation by C. atrox venom as has been seen in vitro in a recently developed rabbit model of envenomation. Compared with unmodified human fibrinogen, CO/Fe modified fibrinogen administered prior to envenomation had significantly shorter onset of coagulation and greater strength; however, when administered after envenomation, there was no differences between the two types of fibrinogen. Of interest, when administered after envenomation, both types of fibrinogen delayed the onset of coagulation while increasing plasma clot strength, a mixed effect likely secondary to formation of fibrinogen degradation products. Further preclinical investigations are needed to further define the benefits and risks of the use of fibrinogenolytic enzymes as defibrinogenating agents, as well as the risks of the "biochemical brakes" used to modulate the activity or substrate of the fibrinogenolytic enzyme.

Biological and biochemical characterization of venom from the broad-banded copperhead (Agkistrodon contortrix laticinctus): isolation of two new dimeric disintegrins

Disintegrins represent a family of effective cell-cell and cell-matrix inhibitors by binding to integrin receptors. Integrins are heterodimeric, transmembrane receptors that are the bridges for these cell interactions. Disintegrins have been shown to have many therapeutic implications for the treatment of strokes, heart attacks, and cancer. Two novel heterodimeric disintegrins were isolated from the venom of the broad-banded copperhead (Agkistrodon contortrix laticinctus). Crude venom separated by cation-exchange chromatography resulted in several fractions possessing hemorrhagic, fibrinolytic, gelatinase, and platelet activities. Venom fractions 2-3 and 17-19 showed fibrinolytic activity. Fractions 2-6, 8-11, and 16-21 had hemorrhagic activity. Gelatinase activity was found in fractions 3, 11, and 19. The isolation of laticinstatins 1 and 2 was accomplished by fractionating crude venom using reverse phase chromatography. Data from both SDS-PAGE and N-terminal sequencing determined that laticinstatins 1 and 2 were heterodimeric disintegrins, and both were assayed for their ability to inhibit platelet aggregation in human whole blood. Future functional evaluation of snake venom disintegrins shows considerable promise for elucidating the biochemical mechanisms of integrin-ligand interactions that will allow the development of adequate medications for hemostatic pathologies such as thrombosis, stroke, and cerebral and cardiac accidents. In this study, we are presenting the first report of the purification, and partial characterization of two new dimeric disintegrins isolated from the venom of broad-banded copperhead snakes.

Snake venoms are integrated systems, but abundant venom proteins evolve more rapidly

Background

While many studies have shown that extracellular proteins evolve rapidly, how selection acts on them remains poorly understood. We used snake venoms to understand the interaction between ecology, expression level, and evolutionary rate in secreted protein systems. Venomous snakes employ well-integrated systems of proteins and organic constituents to immobilize prey. Venoms are generally optimized to subdue preferred prey more effectively than non-prey, and many venom protein families manifest positive selection and rapid gene family diversification. Although previous studies have illuminated how individual venom protein families evolve, how selection acts on venoms as integrated systems, is unknown.

Results

Using next-generation transcriptome sequencing and mass spectrometry, we examined microevolution in two pitvipers, allopatrically separated for at least 1.6 million years, and their hybrids. Transcriptomes of parental species had generally similar compositions in regard to protein families, but for a given protein family, the homologs present and concentrations thereof sometimes differed dramatically. For instance, a phospholipase A₂ transcript comprising 73.4 % of the Protobothrops elegans transcriptome, was barely present in the P. flavoviridis transcriptome (<0.05 %). Hybrids produced most proteins found in both parental venoms. Protein evolutionary rates were positively correlated with transcriptomic and proteomic abundances, and the most abundant proteins showed positive selection. This pattern holds with the addition of four other published crotaline transcriptomes, from two more genera, and also for the recently published king cobra genome, suggesting that rapid evolution of abundant proteins may be generally true for snake venoms. Looking more broadly at Protobothrops, we show that rapid evolution of the most abundant components is due to positive selection, suggesting an interplay between abundance and adaptation.

Conclusions

Given log-scale differences in toxin abundance, which are likely correlated with biosynthetic costs, we hypothesize that as a result of natural selection, snakes optimize return on energetic investment by producing more of venom proteins that increase their fitness. Natural selection then acts on the additive genetic variance of these components, in proportion to their contributions to overall fitness. Adaptive evolution of venoms may occur most rapidly through changes in expression levels that alter fitness contributions, and thus the strength of selection acting on specific secretome components.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1832-6) contains supplementary material, which is available to authorized users.

Structural and biochemical characterisation of VaF1, a P-IIIa fibrinogenolytic metalloproteinase from Vipera ammodytes ammodytes venom

A high molecular mass metalloproteinase with α-fibrinogenolytic activity, termed VaF1, was purified from nose-horned viper (Vipera ammodytes ammodytes) venom. Subcutaneous injection of 9 μg of VaF1 did not induce bleeding in rats. Nevertheless, in vitro it degraded collagen IV, nidogen and fibronectin, components of the extracellular matrix, although with low efficacy and narrow specificity. VaF1 would be expected to exert anti-coagulant action, due to its hydrolysis of fibrinogen, factor X, prothrombin and plasminogen, plasma proteins involved in blood coagulation. The enzyme is a single-chain glycoprotein with a molecular mass of 49.7 kDa, as determined by mass spectrometry, and multiple isoelectric points centred at pH 5.8. The complete amino acid sequence of the precursor of VaF1 was deduced by cloning and sequencing its cDNA. Composed of metalloproteinase, disintegrin-like and cysteine-rich domains, VaF1 is a typical P-IIIa subclass snake venom metalloproteinase. Although it possesses a collagen-binding sequence in its disintegrin-like domain, VaF1 displayed no effect on collagen-induced platelet aggregation in vitro. Two consensus N-glycosylation sites are present in the sequence of VaF1, however, the extent of its glycosylation is low, only 5.2% of the total molecular mass. Interestingly, in standard experimental conditions VaF1 is not recognised by antiserum against the whole venom, so it can contribute to post-serotherapy complications, such as ineffective blood coagulation, in the envenomed patient.

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.

Comparative study of anticoagulant and procoagulant properties of 28 snake venoms from families Elapidae, Viperidae, and purified Russell's viper venom-factor X activator (RVV-X)

Snake venoms consist of numerous molecules with diverse biological functions used for capturing prey. Each component of venom has a specific target, and alters the biological function of its target. Once these molecules are identified, characterized, and cloned; they could have medical applications. The activated clotting time (ACT) and clot rate were used for screening procoagulant and anticoagulant properties of 28 snake venoms. Crude venoms from Daboia russellii siamensis, Bothrops asper, Bothrops moojeni, and one Crotalus oreganus helleri from Wrightwood, CA, had procoagulant activity. These venoms induced a significant shortening of the ACT and showed a significant increase in the clot rate when compared to the negative control. Factor X activator activity was also measured in 28 venoms, and D. r. siamensis venom was 5-6 times higher than those of B. asper, B. moojeni, and C. o. helleri from Wrightwood County. Russell's viper venom-factor X activator (RVV-X) was purified from D. r. siamensis venom, and then procoagulant activity was evaluated by the ACT and clot rate. Other venoms, Crotalus atrox and two Naja pallida, had anticoagulant activity. A significant increase in the ACT and a significant decrease in the clot rate were observed after the addition of these venoms; therefore, the venoms were considered to have anticoagulant activity. Venoms from the same species did not always have the same ACT and clot rate profiles, but the profiles were an excellent way to identify procoagulant and anticoagulant activities in snake venoms.

Colombistatin: a disintegrin isolated from the venom of the South American snake (Bothrops colombiensis) that effectively inhibits platelet aggregation and SK-Mel-28 cell adhesion

Snake venoms are complex mixtures of proteins, which affect the vital biologic systems of prey, as well as humans. Envenomation leads to immobilization by paralysis, cardiac, and circulatory failure. These same venom proteins that cause havoc in the physiologic system could be used as therapeutic agents. Disintegrins and disintegrin-like proteins are molecules found in the venom of four snake families (Atractaspididae, Elapidae, Viperidae, and Colubridae). The disintegrins are non-enzymatic proteins that inhibit cell-cell interactions, cell-matrix interactions, and signal transduction. These proteins may have potential in the treatment of strokes, heart attacks, cancers, osteoporosis, and diabetes. The present study describes the isolation and characterization of a disintegrin (colombistatin) found in the venom of the Venezuelan snake mapanare (Bothrops colombiensis). Colombistatin was purified by a two-step high-performance liquid chromatography procedure, which included reverse phase C18 and size exclusion protein Pak 60. Colombistatin inhibited ADP-induced platelet aggregation, human urinary (T24) and skin melanoma (SK-Mel-28) cancer cell adhesion to fibronectin, and cell migration. Colombistatin contained 72 amino acids with a mass of 7.778 kDa as determined by mass spectrometry. Colombistatin could be used as a therapeutic tool in the treatment of melanoma cancers and also thrombotic diseases.

Neutralization of lethality and proteolytic activities of Malayan pit viper (Calloselasma rhodostoma) venom with North American Virginia opossum (Didelphis virginiana) serum

Malayan pit viper (Calloselasma rhodostoma) envenomation is a major health problem in South East Asia. During envenomation, venom components mainly affect the hemostatic system. The sera from the North American Virginia opossums (Didelphis virginiana) were able to neutralize the venom of the Malayan pit viper. These natural inhibitors could be explored as potential therapeutics against envenomations of a variety of venomous snake species in different geographical habitats.

Ammodytase, a metalloprotease from Vipera ammodytes ammodytes venom, possesses strong fibrinolytic activity

Ammodytase, a high molecular mass metalloproteinase with fibrinogenolytic and fibrinolytic activities, was purified from long-nosed viper (Vipera ammodytes ammodytes) venom by gel filtration, affinity and ion-exchange chromatographies. The enzyme is a single-chain glycoprotein with apparent molecular mass of 70 kDa and isoelectric point of 6.6. Ammodytase shows very weak hemorrhagic activity, and only at doses higher than 20 microg. Consistent with this, it partially degrades some components of the extracellular matrix in vitro. It cleaves the Aalpha-chain of fibrinogen preferentially at peptide bonds Glu(441)-Leu(442) and Glu(539)-Phe(540). Its preference for bulky and hydrophobic amino acids at the P1' position in substrates is demonstrated by its hydrolysis of only the Gln(4)-His(5) and Tyr(16)-Leu(17) bonds in the B-chain of insulin. Ammodytase is able to dissolve fibrin clots. It neither activates nor degrades plasminogen and prothrombin, and has no effect on collagen- or ADP-induced platelet aggregation in vitro. LC/MS and MS/MS analyses of its tryptic fragments demonstrated that ammodytase is a P-III class snake venom metalloproteinase composed of metalloproteinase, disintegrin-like and cysteine-rich domains. Its similarity to hemorrhagins from V. a. ammodytes venom, accompanied by very low toxicity, makes ammodytase a promising candidate as an antigen to prepare antisera against these most dangerous components of the viper's venom. Moreover, its ability to degrade fibrin clots suggests its clinical use as an antithrombotic agent.

Characterization of a fibrinolytic enzyme (ussurenase) from Agkistrodon blomhoffii ussurensis snake venom: Insights into the effects of Ca2+ on function and structure

Fibrino(geno)lytic enzymes from snake venoms have been identified as high quality therapeutic agents for treatment of blood clots and strokes. They act on fibrinogen and fibrin, leading to defibrinogenation of blood, lysis of fibrin, and a consequent decrease in blood viscosity. In this work, a fibrinolytic enzyme (ussurenase) from China Agkistrodon blomhoffii Ussurensis snake venom, was purified to homogeneity, identified as a stable 23,367.8 Da monomeric protein, and was identified as a new kind of snake venom metalloproteinase. Ussurenase reacts optimally with fibrin clots at pH 7.5-8.3 and a temperature of 33-41 degrees C. Although many fibrinolytic enzymes are known to be zinc-dependent, measurements from inductively coupled plasma-atomic emission spectroscopy (ICP-AES) reveal that ussurenase is a Ca2+-containing protein with a molar ratio of 1:1 ([Ca2+]:[enzyme]). Ca2+ is crucial to the fibrin clot hydrolysis by ussurenase but also plays an important role in maintaining the structural integrity of the enzyme. The addition of Ca2+ to the apoenzyme induces a conformational change making the environments surrounding the Trp residues of the enzyme more hydrophobic. The presence of Ca2+ also increases the structural stability of ussurenase, so that higher concentrations of the denaturant guanidine hydrochloride are required to denature the native ussurenase compared to the apo-form. UV absorption and CD spectroscopy experiments show that Ca2+ increases the thermostability and changes the secondary structure of ussurenase. All these data suggest that Ca2+ is crucial for the correct folding and activity of ussurenase.

Isolation and characterization of two disintegrins inhibiting ADP-induced human platelet aggregation from the venom of Crotalus scutulatus scutulatus (Mohave Rattlesnake)

Disintegrins and disintegrin-like proteins are molecules found in the venom of four snake families (Atractaspididae, Elapidae, Viperidae, and Colubridae). The disintegrins are nonenzymatic proteins that inhibit cell-cell interactions, cell-matrix interactions, and signal transduction, and may have potential in the treatment of strokes, heart attacks, cancers, and osteoporosis. Prior to 1983, the venom of Crotalus scutulatus scutulatus (Mohave Rattlesnake) was known to be only neurotoxic; however, now there is evidence that these snakes can contain venom with: (1) neurotoxins; (2) hemorrhagins; and (3) both neurotoxins and hemorrhagins. In this study, two disintegrins, mojastin 1 and mojastin 2, from the venom of a Mohave rattlesnake collected in central Arizona (Pinal County), were isolated and characterized. The disintegrins in these venoms were identified by mass-analyzed laser desorption ionization/time-of-flight/time-of-flight (MALDI/TOF/TOF) mass spectrometry as having masses of 7.436 and 7.636 kDa. Their amino acid sequences are similar to crotratroxin, a disintegrin isolated from the venom of the western diamondback rattlesnake (C. atrox). The amino acid sequence of mojastin 1 was identical to the amino acid sequence of a disintegrin isolated from the venom of the Timber rattlesnake (C. horridus). The disintegrins from the Mohave rattlesnake venom were able to inhibit ADP-induced platelet aggregation in whole human blood both having IC50s of 13.8 nM, but were not effective in inhibiting the binding of human urinary bladder carcinoma cells (T24) to fibronectin.

Disintegrin, hemorrhagic, and proteolytic activities of Mohave rattlesnake, Crotalus scutulatus scutulatus venoms lacking Mojave toxin

Venom from the Mohave rattlesnake, Crotalus scutulatus scutulatus, has been reported to be either: (1) neurotoxic; (2) hemorrhagic, or both (3) neurotoxic and hemorrhagic. In this study, 14 Mohave rattlesnakes from Arizona and Texas (USA) were analyzed for the presence of disintegrins and Mojave toxin. All venom samples were analyzed for the presence of hemorrhagic, proteolytic and disintegrin activities. The venoms were each chromatographed by reverse phase and their fractions tested for disintegrin activity. All specimens containing Mojave toxin were the most toxic and lacked proteolytic, hemorrhagic and disintegrin activities. In contrast, the venoms containing these activities lacked Mojave toxin. Two disintegrin genes, scutustatin and mojavestatin, were identified by PCR of genomic sequences. Scutustatin is a highly conserved disintegrin, while mojavestatin shows low conservation to other known disintegrins. Venoms with the highest LD50 measurements lacked both disintegrin genes, while the specimens with intermediate and low LD50 contained both genes. The intermediate LD50 group contained Mojave toxin and both disintegrin genes, but lacked hemorrhagic and disintegrin activity. Our results raise the possibility that scutustatin and mojavestatin are not expressed in the intermediate LD50 group, or that they may not be the same disintegrins responsible for the disintegrin activity found in the venom. Therefore, it is possible that Mohave rattlesnakes may produce more than two disintegrins.

Neutralization of venoms from two Southern Pacific Rattlesnakes (Crotalus helleri) with commercial antivenoms and endothermic animal sera

The Southern Pacific Rattlesnake (Crotalus helleri) is found in southwestern California (USA), southward through north Baja California (MX) into the northern part of southern Baja California (MX). In this study, the venoms from two Southern Pacific Rattlesnakes were characterized. The two venoms were different in color, concentration, and enzyme activities. Two commercial antivenoms neutralized both C. helleri venoms differently. Antivipmyn (Fab2H) and CroFab (FabO) neutralized both venoms but had different ED50. Four times more Fab2H antivenom was required to neutralize the C. helleri venom No. 011-084-009 than the venom from the snake No. 010-367-284. The hemorrhagic activity of two C. helleri venoms were neutralized differently by endothermic animal sera having a natural resistance to hemorrhagic activity of snake venoms. Opossums and Mexican ground squirrel sera did not neutralize the hemorrhagic activity of the venom No. 010-367-284. The sera of gray woodrats and hispid cotton rats neutralized all hemorrhagins in both C. helleri venoms. This is the first reported case in which opossum serum has not neutralized hemorrhagic activity of pit viper venom. Differences in the compositions of C. helleri venoms and their ability to be neutralized may help explain why snakebites are a difficult medical problem to treat and why effective polyvalent antivenoms are difficult to produce.

Cross reactivity of three antivenoms against North American snake venoms

The antivenom in the United States today is in short supply, expensive and may not even be the most effective in neutralizing venoms from snakes in certain geographical locations. The ED(50) is considered to be the best indicator of antivenom efficacy, however, other tests are needed. In this study, three antivenoms (Antivipmyn (Fab(2)H), Crotalidae Polyvalent Immune Fab (Ovine) (FabO) and UCV (FabV) were used to test the effectiveness of neutralization of eight venoms (Agkistrodon piscivorus piscivorus, Bothrops asper, Crotalus adamanteus, C. durissus durissus, C. horridus atricaudatus, C. h. horridus, C. atrox, and C. molossus molossus). Four different assays were used to study the efficacy of the antivenoms: the antihemorrhagic, antigelatinase, antifibrinolytic and antihide powder azure. Fab(2)H antivenom was more effective in neutralizing the enzymatic activities of these eight venoms than FabO and FabV antivenoms.

Chimeric derivative of fibrolase, a fibrinolytic enzyme from southern copperhead venom, possesses inhibitory activity on platelet aggregation

Fibrolase, a metalloproteinase isolated from the venom of Agkistrodon contortrix contortrix (southern copperhead snake), is a direct acting fibrinolytic enzyme that has been used to digest occlusive blood clots in animal models. The snake venom enzyme directly degrades fibrin associated with platelet rich blood clots and does not rely on plasminogen activation. Rethrombosis is a serious complication that is experienced in a significant percentage of patients treated with thrombolytic agents to remove occlusive vascular thrombi. The involvement of platelets in the initiation of rethrombosis is well known. Arg-Gly-Asp-(RGD)-containing agents have been shown to inhibit rethrombosis following thrombus dissolution by plasminogen activators. In an effort to create a more effective fibrinolytic enzyme and to target the enzyme to platelet-rich thrombi, thereby decreasing the potential for rethrombosis, a chimeric derivative of fibrolase has been produced. This report describes the construction and biochemical characterization of the chimeric enzyme and an evaluation of its in vitro activities. The chimera was formed by covalently incorporating an RGD-like peptide into fibrolase. The site of peptide attachment was determined to be a single lysine residue remote from the enzymes active site. Covalent modification of fibrolase with the RGD-like peptide did not inhibit either fibrinolytic activity of the enzyme nor platelet aggregation inhibitory activity of the peptide. The chimera not only retained the same level of enzymatic activity as native fibrolase, but also acquired the ability to inhibit platelet aggregation by binding to the fibrinogen receptor (integrin alphaIIbbeta3) on platelets.

An internet database of crotaline venom found in the United States

Many snake venoms have been shown to be complex mixtures of pharmacologically important molecules, some of which have potential therapeutic value in the treatment of clot-induced ischemia, cancer and other human disorders. The literature contains many references on how venom and/or venom components are being used in medicine. Within the United States, there are 44 subspecies of poisonous snakes. Despite this rather vast diversity, 90% of the venom-related biomedical research conducted on native snakes found in the United States has been done on a limited number of the more common species. Since the venoms from most of the native species are not available or characterized, their composition and potential usefulness in medicine and applied biomedical research has not been explored. The Natural Toxins Research Center (NTRC) at Texas A&M University-Kingsville has developed a serpentarium that presently houses a population of over 250 snakes composed of 11 species and 20 subspecies. These snakes are cataloged on the Internet database along with their geographical location data, proteolytic activities, high performance liquid chromatography (HPLC) and electrophoretic titration (ET) profiles. Many of these snake venoms have never been characterized and few locale-specific differences within a species have been examined. These venoms can be queried through an on-line search routine. The database will be a useful starting point for anyone interested in isolating fibrinolytic enzymes, specific toxins, hemorrhagins, or other pharmacologically active proteins from snake venoms.

Partial characterization of a basic protein from Crotalus molossus molossus (northern blacktail rattlesnake) venom and production of a monoclonal antibody

The venom of Crotalus molossus molossus (blacktailed rattlesnake) is very basic compared to that of other Crotalinae venoms. Unlike other Crotalinae venoms that are separated by anion exchange chromatography, C. m. molossus venom must be fractionated by cation exchange chromatography. Electrophoretic titration (ET) was used to predict the isoelectric point (pI) and optimal conditions for isolation. The specific hemorrhagic activity for C. m. molossus venom was 7.5 mm/microg, making it one of the most hemorrhagic of Crotalinae venoms. Basic hemorrhagic and fibrinolytic proteins from the venom of C. m. molossus venom were further fractionated by cation exchange chromatography. A basic fibrinolytic/hemorrhagic protein (CMM4) was isolated. CMM4 has a molecular weight between 23 and 26 kDa and a pI of approximately 11.3. SDS electrophoresis revealed one band and ET curve revealed 3 bands with very similar surface charges at all pH. CMM4 did not activate plasminogen when tested with a Chrom Z-PLG assay. The proteins in CMM4 had similar N-terminal amino acid sequences to each other (D-Q-Q-N-L-P-Q-(S/A/R)-Y-(V/R/I)-E-L-V-V-V-A-D-H-R-L-F-M-K-Y-K-S-D-L- N-T). The differences in these proteins are in positions 8 and 10. CMM4 may contain isoforms that differ by minor sequence variations at their amino-termini. The amino acid sequences of CMM4 were very similar to other fibrinolytic and hemorrhagic metalloproteinases isolated from venoms of the genera Crotalus. The specific hemorrhagic activity of CMM4 decreased as the specific fibrinolytic activity increased. A monoclonal antibody (CMM1b) was produced against C. m. molossus venom that neutralized the hemorrhagic activity of some of its fractions. CMM1b also reacted with 11 of 29 venom samples tested via ELISA.

Recurrence phenomena after immunoglobulin therapy for snake envenomations: Part 1. Pharmacokinetics and pharmacodynamics of immunoglobulin antivenoms and related antibodies

The production of immunoglobulin antivenoms has evolved over the past 50 years, resulting in a choice of source animals and highly purified, target-specific immunoglobulin fragments (IgG, Fab2, and Fab). Differences in pharmacokinetic and pharmacodynamic properties of these fragments may affect clinical efficacy. For example, both local and systemic recurrences (worsening after initial improvement) with intact or fragmented immunoglobulin antivenoms have been observed. Local recurrence may result in greater tissue injury, and coagulopathic recurrence may result in the risk of hemorrhage. The latter is of particular concern because coagulopathic recurrence usually occurs after patient discharge. Similar phenomena of symptom recurrence have been observed with ovine, digoxin-specific Fab, and with Fab2 and IgG antivenoms from a variety of source animals as well. Recurrence of venom effects in Fab-treated patients appears to be the result of a pharmacokinetic and pharmacodynamic mismatch between the antivenom and target venom components. That is, tissue penetration and venom neutralization is incomplete, and clearance of unbound antivenom (antivenom that has not bound its venom target) is significantly faster than the clearance of some venom components, allowing signs and symptoms of envenomation to recur. Understanding the relative kinetics and dynamics of immunoglobulins and their targets may allow the physician to anticipate their clinical implications and may suggest modifications of the drug or dose to produce better clinical results.

Epidemiology and hospital course of rattlesnake envenomations cared for at a tertiary referral center in Central Arizona

OBJECTIVE

To describe the demographics and primary inpatient treatment of victims of rattle-snake bites (RSBs) referred to a teritiary referral poison treatment center in central Arizona, and to compare the frequency of local tissue complications and hematologic toxicity during hospitalization in children with those for adults.

METHODS

This was a chart review of patients diagnosed as having RSB by a toxicology service between July 1994 and April 2000. Data collected included: age, sex, date, bite location, time to and length of hospitalization, time to and amount of antivenin, serial hematologic studies, and inpatient complications.

RESULTS

Of 241 patients admitted, 236 charts met inclusion criteria. The majority of RSB victims were male (81%). Children (< or =13 years) represented 22%. Most RSBs (78%) occurred between April and September. Mean time (+/-SEM) to presentation was 1.7 +/- 0.2 hours. Antivenin was administered to 77% of patients, with an average (+/-SEM) of 28.5 +/- 0.9 vials administered. Hematologic abnormalities included: coagulopathy (60%), hypofibrinogenemia (49%), and thrombocytopenia (33%). No statistically significant difference in the above parameters was detected between upper- and lower-extremity envenomations, or between children and adults. Immediate antivenin reactions occurred in 36% of patients. Hemorrhagic bullae formation occurred in 22%, occurring most frequently in upper extremities. Operative procedures were required in 3.4% of patients. Hospitalization averaged 2.5 +/- 0.1 days. There was no fatality.

CONCLUSIONS

In Arizona, RSB victims were typically adult males with upper-extremity bites. Hematologic abnormalities were common. Local tissue complications were more common with upper-extremity envenomations. No statistically significant difference was detected in frequency of hematologic disorders or local tissue complications when children were compared with adults.

Antithrombotic and thrombolytic activities of Agkisacutacin, a snake venom proteinase, in experimental models

The antithrombotic and thrombolytic activities of Agkisacutacin (Agk), a component isolated from Agkistrodon acutus, were determined in vitro and in vivo. The models employed included Chandler's model, arterio-venous shunt model and pulmonary embolus model. The effects of Agkisacutacin on coagulation, plasma fibrinogen and platelet aggregation induced by collagen, adenosine diphosphate (ADP) and thrombin were also investigated. The results showed that Agkisacutacin can significantly inhibit thrombus formation in Chandler's and arterio-venous shunt models, and accelerate thrombolysis of pulmonary emboli in rats. The data suggested that Agkisacutacin possessed antithrombotic and thrombolytic activities. Agkisacutacin was also partial characterized.

Structural and functional characterization of neuwiedase, a nonhemorrhagic fibrin(ogen)olytic metalloprotease from Bothrops neuwiedi snake venom

A fibrino(geno)lytic nonhemorrhagic metalloprotease (neuwiedase) was purified from Bothrops neuwiedi snake venom by a single chromatographic step procedure on a CM-Sepharose column. Neuwiedase represented 4.5% (w/w) of the crude desiccated venom, with an approximate Mr of 20,000 and pI 5.9. As regards the amino acid composition, neuwiedase showed similarities with other metalloproteases, with high proportions of Asx, Glx, Leu, and Ser. Atomic absorption spectroscopy showed that one mole of Zn2+ and one mole of Ca2+ were present per mole of protein. The cDNA encoding neuwiedase was isolated by RT-PCR from venom gland RNA, using oligonucleotides based on the partially determined amino-acid sequences of this metalloprotease. The full sequence contained approximately 594 bp, which codified the 198 amino acid residues with an estimated molecular weight of 22,375. Comparison of the nucleotide and amino acid sequences of neuwiedase with those of other snake venom metalloproteases showed a high level of sequential similarity. Neuwiedase has two highly conserved characteristics sequences H142E143XXH146XXG149XXH152 and C164I165M166. The three-dimensional structure of neuwiedase was modeled based on the crystal structure of Crotalus adamanteus Adamalysin II. This model revealed that the zinc binding site region showed a high structural similarity with other metalloproteases. The proteolyitc specificity, using the Bbeta-chain of oxidized insulin as substrate, was shown to be directed to the Ala14-Leu15 and Tyr16-Leu17 peptide bonds which were preferentially hydrolyzed. Neuwiedase is a Aalpha,Bbeta fibrinogenase. Its activity upon the Aalpha chain of fibrinogen was detected within 15 min of incubation. The optimal temperature and pH for the degradation of both Aalpha and Bbeta chains were 37 degrees C and 7.4-8.0, respectively. This activity was inhibited by EDTA and 1,10-phenantroline. Neuwiedase also showed proteolytic activity upon fibrin and some components of the extracellular matrix. However, it did not show TAME esterase activity and was not able to inhibit platelet aggregation.

Screening for fibrinolytic activity in eight Viperid venoms

Snake venoms contain direct-acting fibrinolytic metalloproteinases (MMP) that could have important applications in medicine. Fibrinolytic enzymes isolated from venom can induce in vitro clot lysis by directly acting on a fibrin clot. The most ideal fibrinolytic enzyme would have high affinity for clots, dissolve clots directly without causing hemorrhage, and would not be neutralized in vivo by endogenous metalloproteinase inhibitors. The purpose of this study was to compare DEAE/HPLC venom profiles from Viperid snakes and identify fractions that contain fibrinolytic activity with no hemorrhagic activity and are not neutralized by animal sera. The sera selected were from four (Virginia opossum, Gray woodrat, Mexican ground squirrel, and Hispid cottonrat) animals known to neutralize hemorrhagic activity in snake venoms. Nineteen fractions from the Viperid venoms had fibrinolytic activity. Agkistrodon venom fractions contained the highest specific fibrinolytic activities. A. piscivorus leucostoma fraction 4 contained a high specific fibrinolytic activity, no hemorrhagic activity, and the fibrinolytic activity was not neutralized by the proteinase inhibitors of the four animal sera. A. contortrix laticinctus fraction 1 also had a high specific fibrinolytic activity and no hemorrhagic activity. However, the fibrinolytic activity was neutralized by Didelphis virginiana (Virginia opossum) serum.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analysis of phospholipase A2 and fibrinolytic enzyme, two enzymes obtained from Chinese Agkistrodon blomhoffii Ussurensis venom

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used to analyze two enzymes, phospholipase A2 and fibrinolytic enzyme isolated from Chinese Agkistrodon blomhoffii Ussurensis venom. Using sinapinic acid as the matrix, positive ion mass spectra of the enzymes were obtained. In addition to the dominant protein [M + H]+ ions, multimeric and multiply charged ions were also observed in the mass spectra. The higher the concentration of the enzymes, the more multiply charged polymer and multimeric ions were detected. Our results indicate that MALDI-TOFMS can provide a rapid and accurate method for molecular weight determination of snake venom enzymes. Mass accuracies of 0.1 and 0.3% were achieved by analysis of highly dialyzed phospholipase A2 and fibrinolytic enzyme, and these results are much better than those obtained using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. MALDI-TOFMS thus provides a reliable method to determine the purity and molecular weight of these enzymes, which are of potential use as therapeutants.

Chimeric fibrolase: covalent attachment of an RGD-like peptide to create a potentially more effective thrombolytic agent

We have prepared an agent possessing both thrombolytic and antiplatelet properties, by conjugating fibrolase, a direct-acting fibrinolytic enzyme isolated from southern copperhead venom, to a peptide which inhibits platelet aggregation. Heterobifunctional coupling reagents, N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP) or sulfosuccinimidyl 6-[alpha-methyl-alpha-(2-pyridyldithio)-toluamido]hexanoate (Sulfo-LC-SMPT), were used in a molar ratio of 10:1 (coupling agent/fibrolase). The N-hydroxy-succinimide of the coupling agent reacts with surface epsilon-amino groups of lysine residues on fibrolase and provides a dithio group that is highly reactive with small thiol compounds. The derivatives obtained in the first reaction contain approximately two moles of 2-pyridyl disulphide per mole of enzyme. These derivatives were then reacted with the free thiol group in an antiplatelet peptide at a molar ratio of 2:1 (peptide/fibrolase). The peptide-fibrolase conjugate was purified by cation exchange HPLC and analyzed by amino acid analysis. The conjugate contains one mole peptide per mole of fibrolase and retains approximately 85% fibrinolytic activity. The IC50 for inhibition of platelet aggregation in human PRP is 300 nM for the conjugate and 67 nM for the antiplatelet peptide. These results demonstrate the successful formation of a novel chimeric protein with bifunctional activity.

Purification of M5, a fibrinolytic proteinase from Crotalus molossus molossus venom that attacks complement

Crotalus molossus molossus (northern blacktailed rattlesnake) venom contains agents that affect blood coagulation. A fibrin(ogen)olytic proteinase, called M5, was isolated and purified from this venom by ion exchange chromatography in a two-step procedure. M5 consists of a single non-glycosylated polypeptide chain with a molecular weight of 25 kDa and an isoelectric point of 7.6. It hydrolyses the A alpha and B beta chains of fibrinogen and the alpha and beta chains of fibrin. It also exhibits caseinolytic activity, but has no effect on synthetic substrates cleaved by thrombin, plasmin, kallikrein, or trypsin. The proteolytic activity of the enzyme against fibrinogen, fibrin, and casein is inhibited by ethylenediaminetetraacetic acid (EDTA) and the loss of activity by EDTA treatment can be prevented by addition of Zn2+. This suggests that M5 is a zinc metalloproteinase. M5, at doses of 50 micrograms and higher, induces significant hemorrhage when injected subcutaneously into mice. In addition, it inactivates guinea-pig complement in a dose-dependent fashion and hydrolyses human C2, C3, and C4.

Hemorrhagic principles in the venom of Bitis arietans, a viperous snake. I. Purification and characterization

Two hemorrhagic principles (Bitis arietans hemorrhagin a and b: abbreviated as BHRa and BHRb) were purified from the venom of the viperous snake Bitis arietans (puff adder) by gel filtration, ion-exchange and absorption chromatography. A 10-fold purification was achieved for BHRa and 7-fold for BHRb with an overall yield of 6.4% of hemorrhagic activity. The hemorrhagins were homogeneous according to disc- and SDS-polyacrylamide gel electrophoresis and immunodiffusion. BHRa and BHRb consist of 623 and 685 amino-acid residues and their apparent molecular weights were 68,000 and 75,000, respectively. They were also immunologically distinct. The purified hemorrhagins express proteolytic activity with heat-denatured casein and hide powder azure. The proteolytic activity with heat-denatured casein was almost the same as that of the crude venom, but that with hide powder azure was less than one-tenth of that of the crude venom. The purified hemorrhagins were free of arginine esterase and phospholipase A2 activities and they are acid labile hemorrhagic toxins. Their hemorrhagic activity was inhibited by EDTA, cysteine and by polyvalent anti-snake serum, but not by phenylmethanesulfonyl fluoride or soybean trypsin inhibitor.

Resolution of isoforms of natural and recombinant fibrolase, the fibrinolytic enzyme from Agkistrodon contortrix contortrix snake venom, and comparison of their EDTA sensitivities

Fibrolase, the fibrinolytic enzyme from Agkistrodon contortrix contortrix snake venom, is a zinc metalloproteinase with a molecular mass of 23 kDa. We report a method to isolate two isoforms of natural fibrolase (fib1 and fib2) and three isoforms of recombinant fibrolase (r-fib1, r-fib2 and r-fib3) using CM 300 cation-exchange high-performance liquid chromatography. Utilizing mass spectrometry we characterized differences in molecular masses of the isoforms of r-fibrolase. These findings suggest that the isoforms differ by minor sequence variations at their amino-termini. Since the stability of fibrolase is exquisitely sensitive to the removal of zinc, we examined the EDTA sensitivity of the isoforms of fibrolase and r-fibrolase to determine if their different chromatographic behavior is related to differences in their zinc affinities. All of the isoforms examined appear to have similar zinc binding affinities. Thus, the IC50 (concentration of EDTA to produce 50% inhibition of enzymatic activity) for fib1 is 160 microM. For the closely related r-fib1, the IC50 is 180 microM. Similarly, r-fib3 has an IC50 of 140 microM.

Purification and characterization of fibrolase isoforms from venom of individual southern copperhead (Agkistrodon contortrix Contortrix) snakes

Fibrolase, a zinc metalloproteinase possessing direct-acting fibrinolytic activity, has been previously purified from southern copperhead (Agkistrodon contortrix contortix) snake venom. We recently reported that a pool of southern copperhead venom from different geographical locations possesses two isoforms of fibrolase (fib1 and fib2) [Loayza, S. L. et al. (1994) J. Chromat. B, in press]. We now report that venom from individual southern copperhead snakes contains the two isoforms which can be separated by a three-step high performance liquid chromatography (HPLC) procedure consisting of hydrophobic interaction chromatography, hydroxylapatite chromatography and weak cation exchange chromatography. Utilizing mass spectrometry we determined that fib1 has a molecular mass of 22,879 atomic mass units (amu) compared to 22,753 amu for fib2. These results support earlier observations during amino acid sequence analysis that a truncated version of the enzyme is produced which is missing the amino-terminal amino acid (< Glu-Arg-Phe-Pro vs. the intact enzyme < Glu-Gln-Arg-Phe-Pro, where < Glu is cyclized glutamine). The truncated version of fibrolase (fib2) has full fibrinolytic activity compared to fib1. EC50 values (concentration of enzyme required to degrade 50% of fibrin in a micro-fibrin plate assay) are 6.4 (+/- 1.0) microM and 5.2 (+/- 0.8) microM for fib 1 and fib2, respectively. Therefore, loss of the amino-terminal amino acid does not appear to influence enzymatic activity. We conclude that the two isoforms of fibrolase arise from variations in the molecular processing of the enzyme by the snake venom gland rather than being caused by the pooling of southern copperhead venoms from different geographical locations.

Activity assays for characterizing the thrombolytic protein fibrolase

Characterization of the thrombolytic agent fibrolase was accomplished employing specific proteolytic and thrombolytic assays. This paper describes a method to measure enzyme proteolytic activity using the oxidized beta-chain of insulin as a substrate. Advantages of this method include a short incubation time for substrate cleavage followed by an isocratic HPLC method with a retention time of approx. 5 min. Proteolytic activity can be rapidly and easily quantitated with this procedure. An azocasein assay was also used to quantitate proteolytic activity. This method was optimized with respect to substrate concentration and incubation time allowing for the rapid quantitation of fibrolase activity. A thrombolytic assay is described which employs fibrin plate clearance and has the advantage of rapid and accurate quantitation compared with previously described methods. It also allows for the standardization of fibrolase in plasmin-equivalent units.

Basic proteinases from Bothrops moojeni (caissaca) venom--II. Isolation of the metalloproteinase MPB. Comparison of the proteolytic activity on natural substrates by MPB, MSP 1 and MSP 2

A basic metalloproteinase active on casein was isolated from Bothrops moojeni venom by chromatography on Sephadex G-100, DEAE-Sephacel, SP-Sephadex C-50 and Sepharose 12. The enzyme, named MPB, is not hemorrhagic and presents only traces of blood-clotting activity. On polyacrylamide gel electrophoresis at pH 4.3, MPB presented a single and diffuse protein band. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the enzyme presented two protein bands corresponding to mol. wts of 65,000 and 55,000, which stained with Schiff's reagent. The proteolytic activity of MPB was inhibited by ethylenediaminetetracetate, 1,10-phenanthroline and dithiothreitol. The proteolytic activity of MPB and the serine proteinases MSP 1 and MSP 2 on natural substrates indicates differences in hydrolytic specificity among these enzymes. All fibrinogen chains were degraded by the three proteinases, but MPB is the most active. On fibrin, the proteinases hydrolyzed only the alpha-chain and alpha-polymer, leaving the beta-chain and gamma-dimer apparently untouched. The native type I collagen was partially hydrolyzed by the three enzymes but no digestion product was detected. On the contrary, calf and guinea-pig skin type I gelatins were readily digested by MSP 1 and MSP 2 producing different hydrolysis patterns. MPB was the least active proteinase on the gelatins. The digestion of fibronectin showed an inversion in the specificity of these proteinases. MPB was the most active on fibronectin, while MSP 1 and MSP 2 promoted a faint, partial hydrolysis on this protein.

Characterization of snake venom components acting on blood coagulation and platelet function

Snake venoms can affect blood coagulation and platelet function in various ways. The physicochemical properties and the mechanisms of actions of the snake venom components affecting blood coagulation and platelet function are discussed.

Inhibition of platelet aggregation by a fibrinogenase from Naja nigricollis venom is independent of fibrinogen degradation

Fibrinogenases, proteinases which release peptides from the carboxy-terminal end of fibrinogen, are classified as alpha-fibrinogenases or beta-fibrinogenases, based on their ability to preferentially attack the A alpha or B beta chain, respectively, of fibrinogen. alpha-Fibrinogenases have been shown to inhibit platelet aggregation whereas beta-fibrinogenases do not. We have studied the inhibition of platelet aggregation by proteinase F1, an alpha-fibrinogenase from Naja nigricollis venom. This proteinase inhibits whole blood aggregation in a dose-dependent manner, with an IC50 value of 145 micrograms. However, the proteinase fails to inhibit aggregation in washed platelet suspensions. Thus, proteinase F1 appears to require a plasma factor to cause inhibition. Since fibrinogen acts as an adhesive protein which links platelets during aggregation, and since proteinase F1 cleaves fibrinogen, we investigated the role of fibrinogen in the inhibition of platelet aggregation by proteinase F1. The degradation products of fibrinogen formed by the proteinase did not cause significant inhibition. Thus, the inhibition of platelet aggregation appears to be independent of the formation of fibrinogen degradation products. We also studied the effect of proteinase F1 on aggregation of platelets that were reconstituted with defibrinogenated plasma. The proteinase inhibited aggregation of platelets even in the absence of plasma fibrinogen. Proteinase F1 was about 4-fold more potent in inhibiting platelet aggregation in defibrinogenated blood. From these results, we conclude that the inhibition of platelet aggregation by proteinase F1 from N. nigricollis venom is independent of its action on fibrinogen.

Purification and characterization of a fibrinolytic enzyme from venom of the southern copperhead snake (Agkistrodon contortrix contortrix)

A fibrinolytic enzyme present in Agkistrodon contortrix contortrix (southern copperhead) venom has been purified by combination of CM-cellulose chromatography, molecular sieve chromatography on Sephadex G-100, p-aminobenzamidine-agarose affinity chromatography, and DEAE-cellulose chromatography. The enzyme, fibrolase, has a molecular weight of 23,000-24,000 and an isoelectric point of pH 6.8. It is composed of approximately 200 amino acids, possesses a blocked NH2-terminus and contains little or no carbohydrate. The enzyme shows no activity against a series of chromogenic p-nitroanilide substrates and is not inhibited by diisopropylfluorophosphate, soybean trypsin inhibitor, Trasylol, or p-chloromercuribenzoate. However, the enzyme is a metalloproteinase since it is inhibited by EDTA, o-phenanthroline and tetraethylenepentamine (a specific zinc chelator). Metal analysis revealed 1 mol of zinc/mol of protein. Study of cleavage site preference of the fibrinolytic enzyme using the oxidized B chain of insulin revealed that specificity is similar to other snake venom metalloproteinases with cleavage primarily directed to an X-Leu bond. Interestingly, unlike some other venom fibrinolytic metalloproteinases, fibrolase exhibits little if any hemorrhagic activity. The enzyme exhibits direct fibrinolytic activity and does not activate plasminogen. In vitro studies revealed that fibrolase dissolves clots made either from purified fibrinogen or from whole blood.

Purification and characterization of the hemorrhagic factor II from the venom of the Bushmaster snake (Lachesis muta muta)

Hemorrhagic factor II (LHF-II) was isolated from Lachesis muta muta (Bushmaster snake) venom using column chromatographies on Sephadex G-100, CM-Sepharose CL-6B and two cycles on Sephadex G-50. This preparation was devoid of phospholipase A2 as well as of the enzymes active on arginine synthetic substrates (TAME and BAPNA) which are present in the crude venom. LHF-II was homogeneous by SDS-polyacrylamide gel electrophoresis, immunodiffusion and immunoelectrophoresis. Also, a single symmetrical boundary with a value of 2.59 S was obtained by ultracentrifugation. LHF-II contains 180 amino acid residues, has a molecular weight of 22,300, and an isoelectric point of 6.6. It contains one gatom zinc and two gatoms calcium per mol protein. The hemorrhagic factor possesses proteolytic activity toward various substrates such as, casein, dimethylcasein, hide powder azure, fibrinogen and fibrin. It hydrolyzes selectively the A alpha-chain of fibrinogen, leaving the B beta- and gamma-chains unaffected. LHF-II is activated by Ca2+ and inhibited by Zn2+. The hemorrhagic as well as the proteinase activity is inhibited by cysteine and by metal chelators such as EDTA, EGTA and 1,10-phenanthroline. Inhibitors of serine proteinases such as phenylmethanesulfonyl fluoride (PMSF) and soybean trypsin inhibitor (SBTI) have no effect on the hemorrhagic factor.

Fibrinolytic enzyme from Agkistrodon halys brevicaudus (Korean mamushi) snake venom

By means of DEAE-Sepharose CL-6B ion exchange chromatography and TSK-GEL G2000 SW high-performance gel filtration, a purified protein with fibrinolytic activity was obtained from the venom of Agkistrodon halys brevicaudus (Korean mamushi). The protein was homogeneous as judged by isoelectric focusing electrophoresis and high-performance gel filtration. Its mol. wt is 39,200 and its isoelectric point 4.12. The specific fibrinolytic activity of the protein was 3.2 times higher than that of the crude venom. The fibrinolytic activity of the purified principle was 33 units/mg protein (units of standard urokinase activity).

HPLC-based two-step purification of fibrinolytic enzymes from the venom of Agkistrodon contortrix contortrix and Agkistrodon piscivorus conanti

In investigations aimed at characterizing snake venom blood clot-dissolving enzymes, we have developed a rapid two-step high-performance chromatography method for the isolation of these fibrinolytic enzymes from the venoms of Agkistrodon contortrix contortrix and Agkistrodon piscivorus conanti. The first step consisted of hydrophobic interaction chromatography on a propyl-aspartamide column. Fractions containing the fibrinolytic activity were then concentrated and applied to a hydroxylapatite column. The resulting preparation, assessed for purity by reverse-phase chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was homogeneous. The molecular weight of both venom fibrinolytic enzymes was approximately 23,000 and amino acid analysis, immunological cross-reaction, cyanogen bromide, and tryptic digestion indicate a significant degree of structural similarity. However, the general proteolytic activity of the A. p. conanti venom enzyme was significantly lower than the corresponding activity of the A. c. contortrix venom, whereas their fibrinolytic activities were quite similar.

Thrombolysis with a snake venom protease in a rat model of venous thrombosis

A fibrin(ogen)olytic protease isolated from the venom of Crotalus atrox (the western diamondback rattlesnake) was tested for thrombolytic activity. The protease, called atroxase, solubilized fibrin when tested on fibrin plates and hydrolyzed fibrinogen rendering it incoagulable with a specific fibrinogenolytic activity of 42 mg fibrinogen/min/mg protein. Atroxase was unable to activate plasminogen. In vivo, fibrinolytic activity was tested on artificial thrombi induced in the posterior vena cava of Sprague-Dawley rats. Thrombolysis was then characterized by angiographic techniques over a period of three hours. Intravenous administration of the protease, at a dosage of 6.0 mg/kg, resulted in thrombolysis within one hour followed by recanalization of the originally occluded vein within two hours. Fibrinogenolytic activity resulted in a 60% decrease in the rat's plasma fibrinogen level. Histological examination of kidney, liver, heart and lung tissue showed no necrosis nor hemorrhage. These results are the first step in evaluating the thrombolytic potential of anticoagulant proteases within C. atrox venom using laboratory animals.

Purification and biochemical characterization of atroxase, a nonhemorrhagic fibrinolytic protease from western diamondback rattlesnake venom

Crotalus atrox venom contains a variety of proteases which render fibrinogen incoagulable and solubilize fibrin. One of these proteases was purified by using ion-exchange and gel permeation liquid chromatography. The protease, called atroxase, consists of a single nonglycosylated polypeptide chain with a molecular weight of 23,500 and an isoelectric point of pH 9.6. Amino acid analysis indicates atroxase to contain 206 residues with no sulfhydryl groups. Metal analysis found zinc and potassium at 1 mol/mol of protein, and calcium at 0.3 mol/mol of protein. Proteolytic activity is inhibited by ethylenediaminetetraacetate and alpha 2-macroglobulin. Maximal proteolytic activity occurs at pH 9.0 and 55 degrees C. Proteolytic specificity, using oxidized insulin B chain, is similar to that of several hemorrhagic toxins found within the same venom, yet atroxase shows no hemorrhagic activity and exhibits low lethality when tested on Swiss Webster mice. Atroxase, an A alpha, B beta fibrinogenase, cleaves the A alpha chain of fibrinogen first followed by the B beta chain and shows no effect on the gamma chain. The nonspecific action of the enzyme results in the extensive hydrolysis of fibrinogen which releases a variety of fibrinopeptides. Fibrin solubilization appears to occur primarily from the hydrolysis of alpha-polymer and unpolymerized alpha and beta chains. Although crude venom induces platelet aggregation, atroxase demonstrated no ability to induce or inhibit aggregation.

Isoelectric focusing in immobilized pH gradients of a snake venom fibrinolytic enzyme

A fibrinolytic enzyme with a molecular weight between 23,000 and 25,000 Da has been purified from southern copperhead snake venom. Immobilized pH gradient isoelectric focusing with an ultranarrow pH interval (pH 6.65-6.95) resolved two isoforms of the fibrinolytic enzyme that were not resolved by standard isoelectric focusing. Attempts at purification of the individual isoenzymes by semi-preparative scale IPG and elution of enzyme by macerating the gel yielded only 20-40% recovery of activity. In attempts to improve recovery, a semi-preparative IPG canal-isoelectric focusing technique has been utilized.

Successful treatment with antivenin of marked thrombocytopenia without significant coagulopathy following rattlesnake bite

We cared for two rattlesnake bite victims who developed platelet counts of 21,000/mm3 and 22,000/mm3. Both had only mild defibrination without evidence of intravascular clotting. In both cases, the administration of antivenin was followed promptly by a sustained rise in platelet counts.

Characterization of two hemorrhagic zinc proteinases, toxin c and toxin d, from western diamondback rattlesnake (Crotalus atrox) venom

Two hemorrhagic proteinases from Crotalus atrox venom, hemorrhagic toxin c (Ht-c) and hemorrhagic toxin d (Ht-d), were characterized and compared to one another. The two toxins are zinc metalloproteinases which both have molecular weights of 24,000. Their isoelectric points are slightly acidic, Ht-c being the more basic of the two with an isoelectric point of 6.2, whereas Ht-d has an isoelectric point of 6.1. Only minor differences were found in the amino acid compositions of the two toxins. The toxins were both demonstrated to be hemorrhagic, using an in vivo assay, and also proteolytic. Prior treatment of the hemorrhagic proteinases with ethylenediaminetetraacetic acid and o-phenanthroline eliminated both the hemorrhagic and the proteolytic activities. Aprotinin and phenylmethylsulfonyl fluoride had no effect upon these activities. The pH optimum of the proteolysis by Ht-c and Ht-d on hide powder azure as the substrate was between pH 8 and pH 9. The circular dichroism spectra for Ht-c and Ht-d appear almost identical with respect to minima positions and elipticities, indicative of very similar solution structures for the two enzymes. Antiserum raised in mice against Ht-c was assayed on double-diffusion Ouchterlony plates for cross-reactivity with other hemorrhagic toxins from C. atrox venom. From this experiment it was concluded that the two hemorrhagic proteinases Ht-c and Ht-d share identical antigenic structures. This was corroborated by tryptic mapping of the two toxins. Only one major difference was observed from the maps. In the case of Ht-c, it was determined that an aspartate was substituted by an alanine when compared to Ht-d. From these characterization studies we conclude that Ht-c and Ht-d are isoenzymes with only very minor differences in their structures.

Substrate specificities and inhibition of two hemorrhagic zinc proteases Ht-c and Ht-d from Crotalus atrox venom

The proteolytic specificities of two zinc hemorrhagic toxins (Ht-c and Ht-d), isolated from Crotalus atrox venom, were investigated by using the oxidized B chain of bovine insulin and synthetic peptide substrates. The enzymes cleaved the Ala14-Leu15 bond of the insulin B chain most rapidly and the Tyr16-Leu17 slightly more slowly. The His5-Leu6, His10-Leu11, and Gly23-Phe24 bonds were also cleaved but at considerably slower rates. In order to assess the substrate length preferences of the enzymes, peptide analogs of the B chain about the Ala14-Leu15 bond were synthesized ranging in length from four to seven residues. The heptapeptide NH2-Leu-Val-Glu-Ala-Leu-Tyr-Leu-COOH was the best peptide substrate tested with the other peptides having decreasing kcat/Km values with decreasing length. The tetrapeptide NH2-Ala-Leu-Tyr-Leu-COOH was not cleaved by the enzymes. Furthermore, this peptide was shown to serve as a competitive inhibitor of the toxins. The N-acetylated pentapeptides and hexapeptides, synthesized to probe the active site environment of the enzymes, were significantly better substrates than their unacetylated counterparts. The toxins had the highest kcat/Km values for the acetylated peptide Ac-Val-Ala-Leu-Leu-Ala-COOH. The data suggest that the toxins may indeed have extended substrate-binding sites, which may accommodate at least six amino acid residues. The best substrate examined thus far for the toxins is the fluorogenic peptide analog 2-aminobenzoyl-Ala-Gly-Leu-Ala-4-nitrobenzylamide, suggestive of similarities between the toxins and mammalian collagenases as well as thermolysin. Mechanisms for inhibition of the enzymes were investigated using amino acid hydroxamates, chloromethyl esters, phosphoramidon and the peptide NH2-Ala-Leu-Tyr-Leu-COOH. All of these inhibitors had Ki values in the 10(-4) M range.