Isolation and properties of a blood coagulation factor X activator from the venom of king cobra (Ophiophagus hannah)

Exploring the Diversity and Function of Serine Proteases in Toxicofera Reptile Venoms: A Comprehensive Overview

Toxicofera reptile venoms are composed of several toxins, including serine proteases. These proteases are glycosylated enzymes that affect the prey's hemostatic system. Their actions extend across the coagulation cascade, the kallikrein-kinin system, and platelet activation. Despite their specificity for different substrates, these enzymes are homologous across all toxicoferans and display high sequence similarity. The aim of this review is to compile decades of knowledge about venom serine proteases, showing the diversity of biochemically and biophysically characterized enzymes, their structural characteristics, advances in understanding their origin and evolution, as well as methods of obtaining enzymes and their biotechnological applications.

Immunoreactivity and neutralization study of Chinese Bungarus multicinctus antivenin and lab-prepared anti-bungarotoxin antisera towards purified bungarotoxins and snake venoms

Bungarus multicinctus is the most venomous snake distributed in China and neighboring countries of Myanmar, Laos, north Vietnam and Thailand. The high mortality rate of B. multicinctus envenomation is attributed to the lethal components of α-, β-, γ- and κ- bungarotoxins contained in the venom. Although anti-B. multicinctus sera were produced in Shanghai, Taiwan and Vietnam, the most widely clinic used product was term as B. multicinctus antivenin and manufactured by Shanghai Serum Bio-technology Co. Ltd. In the present investigation, high purity α-, β- and γ-bungarotoxins were separately isolated from B. multicinctus crude venom. Rabbit anti- α-, β- and γ-bungarotoxin antisera were prepared by common methods, respectively. LD50 values of α-, β- and γ-bungarotoxins were systematically determined via three administration pathways (intraperitoneal, intramuscular and intravenous injections) in Kunming mice. LD50 values of β-bungarotoxin were closely related with injection routines but those of both α- and γ-bungarotoxins were not dependent on the injection routines. Commercial B. multicinctus antivenin showed strong immunoreaction with high molecular weight fractions of the B. multicinctus but weakly recognized low molecular weight fractions like α- and γ-bungarotoxins. Although B. multicinctus antivenin showed immunoreaction with high molecular weight fractions of Bungarus fasciatus, Naja atra, Ophiophagus hannah venoms but the antivenin only demonstrated animal protection efficacy against O. hannah venom. These results indicated that the high molecular weight fractions of the O. hannah played an important role in venom lethality but those of B. fasciatus and N. atra did not have such a role.

The Procoagulant Snake Venom Serine Protease Potentially Having a Dual, Blood Coagulation Factor V and X-Activating Activity

A procoagulant snake venom serine protease was isolated from the venom of the nose-horned viper (Vipera ammodytes ammodytes). This 34 kDa glycoprotein, termed VaaSP-VX, possesses five kDa N-linked carbohydrates. Amino acid sequencing showed VaaSP-VX to be a chymotrypsin-like serine protease. Structurally, it is highly homologous to VaaSP-6 from the same venom and to nikobin from the venom of Vipera nikolskii, neither of which have known functions. VaaSP-VX does not affect platelets. The specific proteolysis of blood coagulation factors X and V by VaaSP-VX suggests that its blood-coagulation-inducing effect is due to its ability to activate these two blood coagulation factors, which following activation, combine to form the prothrombinase complex. VaaSP-VX may thus represent the first example of a serine protease with such a dual activity, which makes it a highly suitable candidate to replace diluted Russell’s viper venom in lupus anticoagulant testing, thus achieving greater reliability of the analysis. As a blood-coagulation-promoting substance that is resistant to serpin inhibition, VaaSP-VX is also interesting from the therapeutic point of view for treating patients suffering from hemophilia.

Snake Venoms in Drug Discovery: Valuable Therapeutic Tools for Life Saving

Animal venoms are used as defense mechanisms or to immobilize and digest prey. In fact, venoms are complex mixtures of enzymatic and non-enzymatic components with specific pathophysiological functions. Peptide toxins isolated from animal venoms target mainly ion channels, membrane receptors and components of the hemostatic system with high selectivity and affinity. The present review shows an up-to-date survey on the pharmacology of snake-venom bioactive components and evaluates their therapeutic perspectives against a wide range of pathophysiological conditions. Snake venoms have also been used as medical tools for thousands of years especially in tradition Chinese medicine. Consequently, snake venoms can be considered as mini-drug libraries in which each drug is pharmacologically active. However, less than 0.01% of these toxins have been identified and characterized. For instance, Captopril^® (Enalapril), Integrilin^® (Eptifibatide) and Aggrastat^® (Tirofiban) are drugs based on snake venoms, which have been approved by the FDA. In addition to these approved drugs, many other snake venom components are now involved in preclinical or clinical trials for a variety of therapeutic applications. These examples show that snake venoms can be a valuable source of new principle components in drug discovery.

Peptide Fraction pOh2 Exerts Antiadipogenic Activity through Inhibition of C/EBP-α and PPAR-γ Expression in 3T3-L1 Adipocytes

Many studies have comprehensively examined the venom of Ophiophagus hannah snake. Its venom comprises different compounds exhibiting a wide range of pharmacological activities. In this investigation, four peptide fractions (PFs), ranging from 3 kDa to 10 kDa, isolated from the Vietnamese snake venom of O. hannah were separated by HPLC and investigated for their inhibitory activity on adipogenesis in 3T3-L1 adipocytes. The most effective PF was then further purified, generating two peptides, pOh1 and pOh2. Upon investigation of these two peptides on 3T3-L1 adipocytes, it was revealed that, at 10 μg/mL, pOh2 was able to inhibit the lipid accumulation in 3T3-L1 adipocytes by up to 56%, without affecting cell viability. Furthermore, the pOh2 downregulated the gene expression of important transcription factors C/EBP-α and PPAR-γ. In addition, aP2 and GPDH adipocyte-specific markers were also significantly reduced compared to untreated differentiated cells. Taken together, pOh2 inhibited the expression of key transcription factors C/EBP-α and PPAR-γ and their target genes, aP2 and GPDH, thereby blocking the adipocyte differentiation. In conclusion, this novel class of peptide might have potential for in vivo antiobesity effects.

Venom-gland transcriptome and venom proteome of the Malaysian king cobra (Ophiophagus hannah)

Background

The king cobra (Ophiophagus hannah) is widely distributed throughout many parts of Asia. This study aims to investigate the complexity of Malaysian Ophiophagus hannah (MOh) venom for a better understanding of king cobra venom variation and its envenoming pathophysiology. The venom gland transcriptome was investigated using the Illumina HiSeq™ platform, while the venom proteome was profiled by 1D-SDS-PAGE-nano-ESI-LCMS/MS.

Results

Transcriptomic results reveal high redundancy of toxin transcripts (3357.36 FPKM/transcript) despite small cluster numbers, implying gene duplication and diversification within restricted protein families. Among the 23 toxin families identified, three-finger toxins (3FTxs) and snake-venom metalloproteases (SVMPs) have the most diverse isoforms. These 2 toxin families are also the most abundantly transcribed, followed in descending order by phospholipases A₂ (PLA₂s), cysteine-rich secretory proteins (CRISPs), Kunitz-type inhibitors (KUNs), and L-amino acid oxidases (LAAOs). Seventeen toxin families exhibited low mRNA expression, including hyaluronidase, DPP-IV and 5’-nucleotidase that were not previously reported in the venom-gland transcriptome of a Balinese O. hannah. On the other hand, the MOh proteome includes 3FTxs, the most abundantly expressed proteins in the venom (43 % toxin sbundance). Within this toxin family, there are 6 long-chain, 5 short-chain and 2 non-conventional 3FTx. Neurotoxins comprise the major 3FTxs in the MOh venom, consistent with rapid neuromuscular paralysis reported in systemic envenoming. The presence of toxic enzymes such as LAAOs, SVMPs and PLA₂ would explain tissue inflammation and necrotising destruction in local envenoming. Dissimilarities in the subtypes and sequences between the neurotoxins of MOh and Naja kaouthia (monocled cobra) are in agreement with the poor cross-neutralization activity of N. kaouthia antivenom used against MOh venom. Besides, the presence of cobra venom factor, nerve growth factors, phosphodiesterase, 5’-nucleotidase, and DPP-IV in the venom proteome suggests its probable hypotensive action in subduing prey.

Conclusion

This study reports the diversity and abundance of toxins in the venom of the Malaysian king cobra (MOh). The results correlate with the pathophysiological actions of MOh venom, and dispute the use of Naja cobra antivenoms to treat MOh envenomation. The findings also provide a deeper insight into venom variations due to geography, which is crucial for the development of a useful pan-regional antivenom.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1828-2) contains supplementary material, which is available to authorized users.

Functional proteomic approach to discover geographic variations of king cobra venoms from Southeast Asia and China

This study deciphers the geographic variations of king cobra (Ophiophagus hannah) venom using functional proteomics. Pooled samples of king cobra venom (abbreviated as Ohv) were obtained from Indonesia, Malaysia, Thailand, and two provinces of China, namely Guangxi and Hainan. Using two animal models to test and compare the lethal effects, we found that the Chinese Ohvs were more fatal to mice, while the Southeast Asian Ohvs were more fatal to lizards (Eutropis multifasciata). Various phospholipases A2 (PLA2s), three-finger toxins (3FTxs) and Kunitz-type inhibitors were purified from these Ohvs and compared. Besides the two Chinese Ohv PLA2s with known sequences, eight novel PLA2s were identified from the five Ohv samples and their antiplatelet activities were compared. While two 3FTxs (namely oh-55 and oh-27) were common in all the Ohvs, different sets of 3FTx markers were present in the Chinese and Southeast Asian Ohvs. All the Ohvs contain the Kunitz inhibitor, OH-TCI, while only the Chinese Ohvs contain the inhibitor variant, Oh11-1. Relative to the Chinese Ohvs which contained more phospholipases, the Southeast Asian Ohvs had higher metalloproteinase, acetylcholine esterase, and alkaline phosphatase activities.

BIOLOGICAL SIGNIFICANCE

Remarkable variations in five king cobra geographic samples reveal fast evolution and dynamic translational regulation of the venom which probably adapted to different prey ecology as testified by the lethal tests on mice and lizards. Our results predict possible variations of the king cobra envenoming to human and the importance of using local antivenin for snakebite treatment.

Hemostatic interference of Indian king cobra (Ophiophagus hannah) Venom. Comparison with three other snake venoms of the subcontinent

Unlike Naja naja, Bungarus caeruleus, Echis carinatus, and Daboia/Vipera russellii venoms, Ophiophagus hannah venom is medically ignored in the Indian subcontinent. Being the biggest poisonous snake, O. hannah has been presumed to inject several lethal doses of venom in a single bite. Lack of therapeutic antivenom to O. hannah bite in India makes any attempt to save the victim a difficult exercise. This study was initiated to compare O. hannah venom with the above said venoms for possible interference in hemostasis. Ophiophagus hannah venom was found to actively interfere in hemostatic stages such as fibrin clot formation, platelet activation/aggregation, and fibrin clot dissolution. It decreased partial thromboplastin time (aPTT), prothrombin time (PT), and thrombin clotting time (TCT). These activities are similar to that shown by E. carinatus and D. russellii venoms, and thus O. hannah venom was found to exert procoagulant activity through the common pathway of blood coagulation, while N. naja venom increased aPTT and TCT but not PT, and hence it was found to exert anticoagulant activity through the intrinsic pathway. Venoms of O. hannah, E. carinatus, and D. russellii lack plasminogen activation property as they do not hydrolyze azocasein, while they all show plasmin-like activity by degrading the fibrin clot. Although N. naja venom did not degrade azocasein, unlike other venoms, it showed feeble plasmin-like activity on fibrin clot. Venom of E. carinatus induced clotting of human platelet rich plasma (PRP), while the other three venoms interfered in agonist-induced platelet aggregation in PRP. Venom of O. hannah least inhibited the ADP induced platelet aggregation as compared to D. russellii and N. naja venoms. All these three venoms showed complete inhibition of epinephrine-induced aggregation at varied doses. However, O. hannah venom was unique in inhibiting thrombin induced aggregation.

Cloning and sequence analysis of an Ophiophagus hannah cDNA encoding a precursor of two natriuretic peptide domains

The king cobra (Ophiophagus hannah) is the largest venomous snake. Despite the components are mainly neurotoxins, the venom contains several proteins affecting blood system. Natriuretic peptide (NP), one of the important components of snake venoms, could cause local vasodilatation and a promoted capillary permeability facilitating a rapid diffusion of other toxins into the prey tissues. Due to the low abundance, it is hard to purify the snake venom NPs. The cDNA cloning of the NPs become a useful approach. In this study, a 957 bp natriuretic peptide-encoding cDNA clone was isolated from an O. hannah venom gland cDNA library. The open-reading frame of the cDNA encodes a 210-amino acid residues precursor protein named Oh-NP. Oh-NP has a typical signal peptide sequence of 26 amino acid residues. Surprisingly, Oh-NP has two typical NP domains which consist of the typical sequence of 17-residue loop of CFGXXDRIGC, so it is an unusual NP precursor. These two NP domains share high amino acid sequence identity. In addition, there are two homologous peptides of unknown function within the Oh-NP precursor. To our knowledge, Oh-NP is the first protein precursor containing two NP domains. It might belong to another subclass of snake venom NPs.

Haemostatically active proteins in snake venoms

Snake venom proteins that affect the haemostatic system can cause (a) lowering of blood coagulability, (b) damage to blood vessels, resulting in bleeding, (c) secondary effects of bleeding, e.g. hypovolaemic shock and organ damage, and (d) thrombosis. These proteins may, or may not, be enzymes. We review the data on the most relevant haemostatically active proteinases, phospholipases A₂, L-amino acid oxidases and 5'-nucleotidases from snake venoms. We also survey the non-enzymatic effectors of haemostasis from snake venoms--disintegrins, C-type lectins and three-finger toxins. Medical applications have already been found for some of these snake venom proteins. We describe those that have already been approved as drugs to treat haemostatic disorders or are being used to diagnose such health problems. No clinical applications, however, currently exist for the majority of snake venom proteins acting on haemostasis. We conclude with the most promising potential uses in this respect.

[Animal toxins and human disease: from single component to venomics, from biochemical characterization to disease mechanisms, from crude venom utilization to rational drug design]

Many animals produced a diversity of venoms and secretions to adapt the changes of environments through the long history of evolution. The components including a large quantity of specific and highly active peptides and proteins have become good research models for protein structure-function and also served as tools and novel clues for illustration of human disease mechanisms. At the same time, they are rich natural resources for new drug development. Through the valuable venomous animal resources of China, researchers at the Kunming Institute of Zoology, CAS have carried out animal toxin research over 30 years. This paper reviews the main work conducted on snake venoms, amphibian and insect secretions, and the development from single component to venomics, from biochemical characterization to human disease mechanisms, from crude venom to rational drug design along with a short perspective on future studies.

A unique group of inactive serine protease homologues from snake venom

A number of inactive serine protease homologues (SPHs), which have poorly understood functions, have been identified in invertebrates and vertebrates. Recently, several SPH transcripts have been reported from snake venom glands, which provide potential new tools for the study of the functions of SPHs. Herein we report for the first time a snake venom serine protease homologue (svSPH) protein, designated as TjsvSPH, isolated from the venom of Trimeresurus jerdonii. Despite its high sequence similarity to snake venom serine proteases (SVSPs), TjsvSPH is devoid of arginine esterase and proteolytic activity. This is probably due to the replacement of Arg-43 by His-43 in the catalytic triad. TjsvSPH did not influence the coagulation time of human plasma, induce human platelet aggregation, inhibit adenosine diphosphate/thrombin-induced human platelet aggregation or increase capillary permeability. Phylogenetic analysis showed that svSPHs were separated from SVSPs and formed an independent group. Structural analysis revealed that the structures of svSPHs are quite different from those of SPHs previously reported. These results indicate that snake venoms contain a unique group of svSPH proteins.

Molecular characterization of l-amino acid oxidase from king cobra venom

An L-amino acid oxidase from Ophiophagus hannah snake venom (Oh-LAAO) was purified by successive gel filtration, ion-exchange and heparin chromatography. Oh-LAAO did not induce platelet aggregation; however, it had potent inhibitory activity on platelet aggregation induced by ADP and U46619, but showed no effect on platelet aggregation induced by thrombin, mucetin, ristocetin and stejnulxin. By RT-PCR and 5'-RACE methods, the complete Oh-LAAO cDNA was cloned from the venom gland total RNA preparations. The cDNA sequence contains an open-reading frame (ORF) of 1476-bp, which encodes a protein of 491 amino acids comprising a signal peptide of 25 amino acids and 466-residue mature protein. The predicted protein sequence of Oh-LAAO was confirmed by N-terminal and trypsin-digested internal peptides sequencing together with peptide mass fingerprinting. cDNAs encoding for ORF of LAAOs from Bungarus fasciatus and B. multicinctus were cloned and reported in this study. In addition, partial cDNA encoding for Naja atra LAAO was also reported. Oh-LAAO shared approximately 50% protein sequence identity with other known snake venom LAAOs. Phylogenetic analysis indicated that Oh-LAAO is evolutionary distant to other snake venom LAAOs.

Molecular cloning of serine proteases from elapid snake venoms

Serine proteases are widely distributed in viperid snake venoms, but rare in elapid snake venoms. Previously, we have identified a fibrinogenolytic enzyme termed OhS1 from the venom of Ophiophagus hannah. The results indicated that OhS1 might be a serine protease, but there was no structural evidence previously. In the present study, the primary structure of OhS1 was determined by protein sequencing, in combination with RT-PCR and 5'-RACE methods. OhS1 precursor is composed of an 18-amino acid signal peptide, a 6-amino acid putative activation peptide and 236-amino acid mature protein. OhS1 homologues from Naja atra and Bungarus multicinctus were also cloned and reported. These elapid venom serine proteases exhibited approximately 60% sequence identity with serine proteases from the snake venoms of the Viperidae and Colubridae family. Phylogenetic analysis indicated that snake venom serine protease might have a common ancestor.

Isolation and cloning of a metalloproteinase from king cobra snake venom

A 50 kDa fibrinogenolytic protease, ohagin, from the venom of Ophiophagus hannah was isolated by a combination of gel filtration, ion-exchange and heparin affinity chromatography. Ohagin specifically degraded the alpha-chain of human fibrinogen and the proteolytic activity was completely abolished by EDTA, but not by PMSF, suggesting it is a metalloproteinase. It dose-dependently inhibited platelet aggregation induced by ADP, TMVA and stejnulxin. The full sequence of ohagin was deduced by cDNA cloning and confirmed by protein sequencing and peptide mass fingerprinting. The full-length cDNA sequence of ohagin encodes an open reading frame of 611 amino acids that includes signal peptide, proprotein and mature protein comprising metalloproteinase, disintegrin-like and cysteine-rich domains, suggesting it belongs to P-III class metalloproteinase. In addition, P-III class metalloproteinases from the venom glands of Naja atra, Bungarus multicinctus and Bungarus fasciatus were also cloned in this study. Sequence analysis and phylogenetic analysis indicated that metalloproteinases from elapid snake venoms form a new subgroup of P-III SVMPs.

Anticoagulant effect of Naja naja venom 5′nucleotidase: Demonstration through the use of novel specific inhibitor, vanillic acid

The snake venom proteins affect hemostasis by either advancing/delaying blood coagulation. Apart from proteases and phospholipase A(2)s (PLA(2)s), 5'nucleotidase is known to affect hemostasis by inhibiting platelet aggregation. In this study, the possible involvement of Naja naja venom 5'nucleotidase in mediating anticoagulant affect is evaluated. Vanillic acid selectively and specifically inhibited 5'nucleotidase activity among other enzymes present in N. naja venom. It is a competitive inhibitor as evident of inhibition relieving upon increased substrate concentration. Vanillic acid dose dependently inhibited the anticoagulant effect of N. naja venom up to 40%. This partial involvement of 5'nucleotidase in mediating anticoagulant effect is substantiated by concanavalin-A (Con-A) inhibition studies. Con-A, competitively inhibited in vitro protease and 5'nucleotidase activity up to 100%. However, it did not exhibit inhibitory activity on PLA(2). The complete inhibition of anticoagulant effect by Con-A upon recalcification time suggests the participation of both 5'nucleotidase and protease in mediating anticoagulant effect of N. naja venom. Vanillic acid and Con-A inhibition studies together suggest that probably 5'nucleotidase interacts with one or more factors of intrinsic pathway of blood coagulation to bring about anticoagulant effect. Thus, this study for the first time demonstrates the involvement of 5'nucleotidase in mediating N. naja venom anticoagulant effect.

Characterization and molecular cloning of dabocetin, a potent antiplatelet C-type lectin-like protein from Daboia russellii siamensis venom

A novel C-type lectin-like protein, dabocetin, was purified from Daboia russellii siamensis venom. On SDS-polyacrylamide gel electrophoresis, it showed a single band with an apparent molecular weight of 28 kDa and two distinct bands with the apparent molecular weights of 15.0 kDa and 14.5 kDa under non-reducing and reducing conditions, respectively. cDNA clones containing the coding sequences for dabocetin alpha and beta subunits were isolated and sequenced. The deduced protein sequences of both subunits were confirmed by N-terminal amino acid sequencing and trypsin-digested peptide mass fingerprinting. Dabocetin did not induce platelet aggregation in platelet-rich plasma. It also had little effect on the platelet aggregation induced by ADP, TMVA or stejnulxin. Whereas, dabocetin inhibited ristocetin-induced platelet agglutination in platelet-rich plasma in a dose-dependent manner with an IC50 value of 0.35 microM. Flow cytometry analysis showed that dabocetin significantly inhibited mAb SZ2 binding to platelet membrane glycoprotein Ib alpha, indicating that platelet membrane glycoprotein Ib is involved in the inhibitory effect of dabocetin on ristocetin-induced platelet agglutination.

Molecular characterization of a weak fibrinogen-clotting enzyme from Trimeresurus jerdonii venom

A fibrinogen-clotting enzyme designed as jerdonobin-II was isolated from the venom of Trimeresurus jerdonii. It differed in molecular weight and N-terminal sequence with the previously isolated jerdonobin, a thrombin-like enzyme from the same venom. The enzyme consists of a single polypeptide chain with molecular weights of 30,000 and 32,000 under non-reducing and reducing conditions, respectively. Jerdonobin-II showed weak fibrinogen clotting activity and its activity unit on fibrinogen was calculated to be less than one unit using human thrombin as standard. The precursor protein sequence of jerodonobin-II was deduced from cloned cDNA sequence. The sequence shows high similarity (identity=89%) to TSV-PA, a specific plasminogen activator from venom of T. stejnegeri. Despite of the sequence similarity, jerdonobin-II was found devoid of plasminogen activating effect. Sequence alignment analysis suggested that the replacement of Lys239 in TSV-PA to Gln239 in jerdonobin-II might play an important role on their plasminogen activating activity difference.

Cloning and purification of α-neurotoxins from king cobra (Ophiophagus hannah)

Thirteen complete and three partial cDNA sequences were cloned from the constructed king cobra (Ophiophagus hannah) venom gland cDNA library. Phylogenetic analysis of nucleotide sequences of king cobra with those from other snake venoms revealed that obtained cDNAs are highly homologous to snake venom alpha-neurotoxins. Alignment of deduced mature peptide sequences of the obtained clones with those of other reported alpha-neurotoxins from the king cobra venom indicates that our obtained 16 clones belong to long-chain neurotoxins (seven), short-chain neurotoxins (seven), weak toxin (one) and variant (one), respectively. Up to now, two out of 16 newly cloned king cobra alpha-neurotoxins have identical amino acid sequences with CM-11 and Oh-6A/6B, which have been characterized from the same venom. Furthermore, five long-chain alpha-neurotoxins and two short-chain alpha-neurotoxins were purified from crude venom and their N-terminal amino acid sequences were determined. The cDNAs encoding the putative precursors of the purified native peptide were also determined based on the N-terminal amino acid sequencing. The purified alpha-neurotoxins showed different lethal activities on mice.

In vitro procoagulant and anticoagulant properties of Naja naja naja venom

Bites by the Indian cobra (Naja naja naja) are common in India and Sri Lanka because of its close association with humans. Cobra venoms are complex and contain several toxic components, including neurotoxins that cause post-synaptic neuromuscular blockade with respiratory paralysis and even death. Bites may also cause extensive local necrosis by mechanisms not fully elucidated. Although no significant coagulopathy has been reported, N.n. naja venom can form blood clots in vitro by activating prothrombin as demonstrated by thrombin-specific chromogenic substrate. Scanning electron microscopy demonstrates that the clots formed by venom lack the thin fibrin strands of normal blood clots formed by thromboplastin or glass contact. Rheometry shows that clots formed by venom have abnormally low elasticity over an extended period and then, as the platelets contract, a retarded and more feeble increase in elasticity. Purified N.n. naja venom PLA2 inhibits platelet aggregation in PRP and explains the decreased clot retraction and retarded and compromised elasticity build up. The present study shows that the PLA2 and the prothrombin activator from N.n. naja venom have effects on haemostasis and blood clotting, although such effects are not observed systemically in envenomed humans.

Metalloproteinase with factor X activating and fibrinogenolytic activities from Vipera berus berus venom

We have previously shown that Vipera berus berus venom contains several factor X activating enzymes. In the present study we have investigated one of them. The enzyme was separated from venom by gel filtration on Sephadex G-100 superfine and chromatography on agarose HPS-7 and phenyl-agarose. The enzyme is a glycosylated metalloproteinase containing hexoses, hexosamines and neuraminic acid. The purified factor X activating enzyme consists of two equal chains (59 kDa). The specificity studies have shown that enzyme is nonspecific factor X activating proteinase hydrolysing also proteins such as azocasein, gelatin and fibrinogen. The enzyme hydrolyses oxidized insulin B-chain at the positions Ala(14)-Leu(15) and Tyr(16)-Leu(17) but it is inactive on fibrin, plasminogen and prothrombin. We used 8-10 amino acid residues containing peptides, which reproduce the sequence around the cleavage sites in factor X, factor IX and fibrinogen, as potential substrates for enzyme. Cleavage products of peptide hydrolysis were determined by MALDI-TOF MS. The peptide Asn-Asn-Leu-Thr-Arg-Ile-Val-Gly-Gly-factor X fragment was cleaved by enzyme at positions Leu(3)-Thr(4) and Arg(5)-Ile(6). The fibrinogen peptide fragment Glu-Tyr-His-Thr-Glu-Lys-Leu-Val-Thr-Ser was hydrolysed at position Lys(6)-Leu(7).

Cloning and characterization of a blood coagulation factor IX-binding protein from the venom of Trimeresurus stejnegeri

A blood coagulation factor IX-binding protein (TSV-FIX-BP) was isolated from the snake venom of Trimeresurus stejnegeri. On SDS-polyacrylamide gel electrophoresis, TSV-FIX-BP showed a single band with an apparent molecular weight of 23,000 under non-reducing conditions, and two distinct bands with apparent molecular weights of 14,800 and 14,000 under reducing conditions. cDNA clones containing the coding sequences of TSV-FIX-BP were isolated and sequenced to determine the structure of the precursors of TSV-FIX-BP subunits. The deduced amino acid sequences of two subunits of TSV-FIX-BP were confirmed by N-terminal protein sequencing and trypsin-digested peptide mass fingerprinting. TSV-FIX-BP was a non-enzymatic C-type lectin-like anti-coagulant. The anti-coagulant activity of TSV-FIX-BP was mainly caused by its dose dependent interaction with blood coagulation factor IX but not with blood coagulation factor X.

Factor X activator from Vipera lebetina snake venom, molecular characterization and substrate specificity

Our studies of the venom from the Levantine viper Vipera lebetina have demonstrated the existence of both coagulants and anticoagulants of the hemostatic system in the same venom. We showed that V. lebetina venom contains factor X activator (VLFXA) and factor V activator, fibrinolytic enzymes. VLFXA was separated by gel filtration on Sephadex G-100 superfine and ion exchange chromatography on CM-cellulose and on TSK-DEAE (for HPLC) columns. VLFXA is a glycoprotein composed of a heavy chain (57.5 kDa) and two light chains (17.4 kDa and 14.5 kDa) linked by disulfide bonds. VLFXA has multiple molecular forms distinguished by their isoelectric points. The differences in their pI values may be caused by dissimilarities in the respective charged carbohydrate content or in the primary sequence of amino acids. We synthesized 6-9 amino acid residues containing peptides according to physiological cleavage regions of human factor X and human factor IX. The peptides (Asn-Asn-Leu-Thr-Arg-Ile-Val-Gly-Gly - factor X fragment, and Asn-Asp-Phe-Thr-Arg-Val-Val-Gly-Gly - factor IX fragment) were used as substrates for direct assay of VLFXA. Cleavage products of peptide hydrolysis and the molecular masses of cleavage products of human factor X were determined by MALDI-TOF MS. The MALDI-TOF MS was highly efficient for the recovery and identification of peptides released by VLFXA hydrolysis. We can conclude that VLFXA cleaves the Arg(52)-Ile(53) bond in the heavy chain of human factor X and the Arg(226)-Val(227) bond in human factor IX precursor. VLFXA could not activate prothrombin nor had any effect on fibrinogen, and it had no arginine esterase activity toward benzoylarginine ethyl ester.

Hematological studies on DIC-like findings observed in patients with snakebite in south China

To clarify the characteristics of the hematological disturbances evoked by snakebite, we measured the antithrombin III (AT-III) activity, alpha2-plasmin inhibitor (alpha2-PI) activity, fibrinogen concentration (Fg) and level of fibrin degradation products (FDP) in 21 patients envenomed by several snakes in south China between August 1998 and October 1999. The hematological changes observed were as follows: the mean activities of AT-III were decreased in patients bitten by Ophiophagus hannah (Oh.), Bungarus fasciatus (Bf.), Hydrophis cyanocinctus (Hc.), Rhabdophis subminiatus (Rs.), and Trimeresurus stejnegeri (Ts.), while those of alpha2-PI were decreased in all patients in the present study; Fg was not detectable in the case of Rs. bite, and the Fg concentration after Ts., Oh., Hc. and Bf. bites also decreased markedly thereby increasing the mean levels of FDP in all patients. It thus appeared that DIC-like syndrome was caused in patients envenomed by snakebite. In the present study, we found that patients who were bitten by Rs., which is still being classified as a non-venomous snake, exhibited complete defibrinogenation and severe hemorrhage without any evidence of severe multiple organ damage. We also found that patients with Ts. bite showed marked hemostatic disturbance without severe multiple organ damage. It is considered that such a discrepancy between the hematological findings and clinical symptoms could be a characteristic phenomenon of the DIC-like syndrome induced by snakebite, especially by Rs. and Ts. bites.

Snake venoms and the hemostatic system

Snake venoms are complex mixtures containing many different biologically active proteins and peptides. A number of these proteins interact with components of the human hemostatic system. This review is focused on those venom constituents which affect the blood coagulation pathway, endothelial cells, and platelets. Only highly purified and well characterized snake venom proteins will be discussed in this review. Hemostatically active components are distributed widely in the venom of many different snake species, particularly from pit viper, viper and elapid venoms. The venom components can be grouped into a number of different categories depending on their hemostatic action. The following groups are discussed in this review: (i) enzymes that clot fibrinogen; (ii) enzymes that degrade fibrin(ogen); (iii) plasminogen activators; (iv) prothrombin activators; (v) factor V activators; (vi) factor X activators; (vii) anticoagulant activities including inhibitors of prothrombinase complex formation, inhibitors of thrombin, phospholipases, and protein C activators; (viii) enzymes with hemorrhagic activity; (ix) enzymes that degrade plasma serine proteinase inhibitors; (x) platelet aggregation inducers including direct acting enzymes, direct acting non-enzymatic components, and agents that require a cofactor; (xi) platelet aggregation inhibitors including: alpha-fibrinogenases, 5'-nucleotidases, phospholipases, and disintegrins. Although many snake venoms contain a number of hemostatically active components, it is safe to say that no single venom contains all the hemostatically active components described here. Several venom enzymes have been used clinically as anticoagulants and other venom components are being used in pre-clinical research to examine their possible therapeutic potential. The disintegrins are an interesting group of peptides that contain a cell adhesion recognition motif, Arg-Gly-Asp (RGD), in the carboxy-terminal half of their amino acid sequence. These agents act as fibrinogen receptor (integrin GPIIb/IIIa) antagonists. Since this integrin is believed to serve as the final common pathway leading to the formation of platelet-platelet bridges and platelet aggregation, blockage of this integrin leads to inhibition of platelet aggregation regardless of the stimulating agent. Clinical trials suggest that platelet GPIIb/IIIa blockade is an effective therapy for the thrombotic events and restenosis frequently accompanying cardiovascular and cerebrovascular disease. Therefore, because of their clinical poten tial, a large number of disintegrins have been isolated and characterized.