Purification and some properties of two proteinases from Crotalus adamanteus venom that inactivate human alpha 1-proteinase inhibitor

Constructing comprehensive venom proteome reference maps for integrative venomics

OBJECTIVE

Understanding the molecular basis of complex adaptive traits, such as snake venom, demands qualitative and quantitative comparisons of the temporal and spatial patterns of venom variation. Here, we assessed the proof-of-concept that locus-resolved reference venom proteome maps can be achieved through efficient pre-MS venom proteome decomplexation, peptide-centric MS/MS analysis and species-specific database searching.

METHODS

Venom proteome components were fractionated and quantified by RP-HPLC, SDS-PAGE and 2DE prior to LC-MS/MS matching against a species-specific transcriptomic dataset.

RESULTS

Combination of RP-HPLC/SDS-PAGE and 2DE followed by LC-MS/MS showed the existence of ∼178-180 venom protein species generated from ∼48 unique transcripts.

CONCLUSIONS

Our results underscore that if sufficient pre-MS and MS efforts are applied, comprehensive venom maps can be achieved. And - equally important - dissociating the venom decomplexing steps from the protein identification process represents the key to achieving a quantitative and locus-resolved insight of the venom proteome.

Prediction of Toxin Genes from Chinese Yellow Catfish Based on Transcriptomic and Proteomic Sequencing

Fish venom remains a virtually untapped resource. There are so few fish toxin sequences for reference, which increases the difficulty to study toxins from venomous fish and to develop efficient and fast methods to dig out toxin genes or proteins. Here, we utilized Chinese yellow catfish (Pelteobagrus fulvidraco) as our research object, since it is a representative species in Siluriformes with its venom glands embedded in the pectoral and dorsal fins. In this study, we set up an in-house toxin database and a novel toxin-discovering protocol to dig out precise toxin genes by combination of transcriptomic and proteomic sequencing. Finally, we obtained 15 putative toxin proteins distributed in five groups, namely Veficolin, Ink toxin, Adamalysin, Za2G and CRISP toxin. It seems that we have developed a novel bioinformatics method, through which we could identify toxin proteins with high confidence. Meanwhile, these toxins can also be useful for comparative studies in other fish and development of potential drugs.

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.

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

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

Snake venom hemorrhagins

Viperine and crotaline snake venoms contain one or more hemorrhagic principles called hemorrhagins. These are zinc-containing metalloproteases characterized by the presence of a protease domain, with additional domains in some of them. They act essentially by degrading the component proteins of basement membrane underlying capillary endothelial cells. The toxins also act on these cells causing lysis or drifting apart, resulting in hemorrhage per rhexis or per diapedesis. Some of these toxins have been found to exert additional effects such as fibrinogenolysis and platelet aggregation that facilitate hemorrhage. The structural and functional features of this class of toxins have been discussed in this review in an attempt to get a better understanding of their toxicity. This can be of immense therapeutic value in the management of snake venom poisoning, as hemorrhagins are among the major lethal factors in snake venom.

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.

Structures of adamalysin II with peptidic inhibitors. Implications for the design of tumor necrosis factor alpha convertase inhibitors

Crotalus adamanteus snake venom adamalysin II is the structural prototype of the adamalysin or ADAM family comprising proteolytic domains of snake venom metalloproteinases, multimodular mammalian reproductive tract proteins, and tumor necrosis factor alpha convertase, TACE, involved in the release of the inflammatory cytokine, TNFalpha. The structure of adamalysin II in noncovalent complex with two small-molecule right-hand side peptidomimetic inhibitors (Pol 647 and Pol 656) has been solved using X-ray diffraction data up to 2.6 and 2.8 A resolution. The inhibitors bind to the S'-side of the proteinase, inserting between two protein segments, establishing a mixed parallel-antiparallel three-stranded beta-sheet and coordinate the central zinc ion in a bidentate manner via their two C-terminal oxygen atoms. The proteinase-inhibitor complexes are described in detail and are compared with other known structures. An adamalysin-based model of the active site of TACE reveals that these small molecules would probably fit into the active site cleft of this latter metalloproteinase, providing a starting model for the rational design of TACE inhibitors.

2 angstrom X-ray structure of adamalysin II complexed with a peptide phosphonate inhibitor adopting a retro-binding mode

The search of reprolysin inhibitors offers the possibility of intervention against both matrixins and ADAMs. Here we report the crystal structure of the complex between adamalysin II, a member of the reprolysin family, and a phosphonate inhibitor modeled on an endogenous venom tripeptide. The inhibitor occupies the primed region of the cleavage site adopting a retro-binding mode. The phosphonate group ligates the zinc ion in an asymmetric bidentate mode and the adjacent Trp indole system partly fills the primary specificity subsite S1'. An adamalysin-based model of tumor necrosis factor-alpha-converting enzyme (TACE) reveals a smaller S1' pocket for this enzyme.

Proteolytic specificity of rhodostoxin, the major hemorrhagin of Calloselasma rhodostoma (Malayan pit viper) venom

The proteolytic specificity of rhodostoxin, the major hemorrhagin from Calloselasma rhodostoma (Malayan pit viper) venom was investigated using oxidized B-chain of bovine insulin as substrate. Six peptide bonds were cleaved: Ser9-Hist10, His10-Leu11, Ala14-Leu15, Tyr16-Leu17, Gly20-Glu21 and Phe24-Phe25. Deglycosylated rhodostoxin, however, cleaved primarily at Arg22-Gly23.

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.

The metzincins--topological and sequential relations between the astacins, adamalysins, serralysins, and matrixins (collagenases) define a superfamily of zinc-peptidases

The three-dimensional structures of the zinc endopeptidases human neutrophil collagenase, adamalysin II from rattle snake venom, alkaline proteinase from Pseudomonas aeruginosa, and astacin from crayfish are topologically similar, with respect to a five-stranded beta-sheet and three alpha-helices arranged in typical sequential order. The four proteins exhibit the characteristic consensus motif HEXXHXXGXXH, whose three histidine residues are involved in binding of the catalytically essential zinc ion. Moreover, they all share a conserved methionine residue beneath the active site metal as part of a superimposable "Met-turn." This structural relationship is supported by a sequence alignment performed on the basis of topological equivalence showing faint but distinct sequential similarity. The alkaline proteinase is about equally distant (26% sequence identity) to both human neutrophil collagenase and astacin and a little further away from adamalysin II (17% identity). The pairs astacin/adamalysin II, astacin/human neutrophil collagenase, and adamalysin II/human neutrophil collagenase exhibit sequence identities of 16%, 14%, and 13%, respectively. Therefore, the corresponding four distinct families of zinc peptidases, the astacins, the matrix metalloproteinases (matrixins, collagenases), the adamalysins/reprolysins (snake venom proteinases/reproductive tract proteins), and the serralysins (large bacterial proteases from Serratia, Erwinia, and Pseudomonas) appear to have originated by divergent evolution from a common ancestor and form a superfamily of proteolytic enzymes for which the designation "metzincins" has been proposed. There is also a faint but significant structural relationship of the metzincins to the thermolysin-like enzymes, which share the truncated zinc-binding motif HEXXH and, moreover, similar topologies in their N-terminal domains.

Hemorrhagic metalloproteinases from snake venoms

One of the more significant consequences of crotalid envenomation is hemorrhage. Over the past 50 years of investigation, it is clear that the primary factors responsible for hemorrhage are metalloproteinases present in the venom of these snakes. The biochemical basis for their activity is the proteolytic destruction of basement membrane and extracellular matrix surrounding capillaries and small vessels. These proteinase toxins may also interfere with coagulation, thus complementing loss of blood from the vasculature. Structural studies have shown that these proteinases are synthesized as zymogens and are processed at both the amino and carboxy termini to give the mature protein. The variety of hemorrhagic toxins found in snake venoms is due to the presence of structurally related proteins composed of various domains. The type of domains found in each toxin plays an important role in the hemorrhagic potency of the protein. Recently, structural homologs to the venom hemorrhagic metalloproteinases have been identified in several mammalian reproductive systems. The functional significance of the reproductive proteins is not clear, but in light of the presence of similar domains shared with the venom metalloproteinases, their basic biochemical activities may be similar but with very different consequences. This review discusses the history of hemorrhagic toxin research with emphasis on the Crotalus atrox proteinases. The structural similarities observed among the hemorrhagic toxins are outlined, and the structural relationships of the toxins to the mammalian reproductive proteins are described.

Activation of snake venom metalloproteinases by a cysteine switch-like mechanism

The cDNAs of several snake venom zinc endopeptidases code for a putative propeptide, which includes the conserved cysteine-containing sequence PKMCGVT. It has been suggested that binding of the cysteine thiol function to the active-site zinc, resulting in inactivation of the catalytic domain, occurs in a mode similar to the 'cysteine switch' mechanism proposed for matrix metalloproteinases. In order to confirm this hypothesis, inhibition kinetics have been performed on the metalloproteinase adamalysin II of the venom of the snake Crotalus adamanteus using several cysteine peptides. Among these the synthetic hexapeptide PKMCGV-NH2, corresponding to the conserved sequence portion of the known propeptides, was found to be by far the strongest inhibitor of this proteinase with a Ki of 3.4 microM. The inhibitory potencies of an equivalent peptide with the L-Cys replaced by a D-Cys or by an L-Ser as well as of reduced glutathione, cysteine and two unrelated cysteine peptides were by one to two orders of magnitudes lower. These findings strongly support a cysteine switch-like mechanism even for activation of the snake venom metalloproteinases.

Opossum serum alpha 1-proteinase inhibitor: purification, linear sequence, and resistance to inactivation by rattlesnake venom metalloproteinases

Opossum (Didelphis virginiana) serum was fractionated with (NH4)2SO4 and then chromatographed on DEAE-Sepharose and phenyl-Sepharose. Affinity chromatography on a protein A-Sepharose-antibody column removed traces of opossum serum metalloproteinase inhibitors, and resulted in a homogeneous preparation of opossum alpha 1-proteinase inhibitor (alpha 1-PI). The inhibitor is a single-chain glycoprotein (17.7% carbohydrate) with an estimated M(r) = 54,000. An opossum liver cDNA library was immunoscreened, and clones containing cDNA encoding for the open reading frame for opossum alpha 1-PI were isolated. The cDNA inserts contained nucleotide sequences corresponding to the amino-terminal and an internal peptide sequence of opossum alpha 1-PI which had been separately determined by protein sequence analysis. The entire inserts coded for a protein consisting of a 21-residue signal peptide and a 389-residue mature protein. Opossum alpha 1-PI shows 51-58% identity with other mammalian alpha 1-PI amino acid sequences, and the conserved residues expected for a member for the serpin family have been retained. The carbohydrate attachment sites and the reactive site residues (M-S) of opossum alpha 1-PI are identical to those of human alpha 1-PI. Opossum alpha 1-PI formed stable enzyme/inhibitor complexes with trypsin, chymotrypsin, and human neutrophil elastase, but did not react with thrombin or with snake venom serine proteinases. Opossum alpha 1-PI was inactivated by papain or Pseudomonas aeruginosa elastase, and electrophoretic analysis of the reaction products indicated limited proteolysis in the reactive site loop of the inhibitor.(ABSTRACT TRUNCATED AT 250 WORDS)

A novel alpha-type fibrinogenase from Agkistrodon rhodostoma snake venom

By means of CM-Sephadex C-50 column chromatography, gel-filtration on sephadex G-75 and Sephacryl S-200 columns, a purified fibrinogenase, kistomin, was obtained from venom of Agkistrodon rhodostoma. It was a single peptide-chain with a molecular mass of about 21,800 Da containing about 202 amino-acid residues as revealed by amino acid analysis. Kistomin preferentially cleaved A alpha- and subsequently the gamma-chain of fibrinogen, leaving the B beta-chain unaffected. Its fibrinogenolytic activity was estimated to be 36.6 +/- 4.5 mg/min per mg protein and was inhibited by the pretreatment of EDTA, suggesting that it is a metalloproteinase. Its fibrinogenolytic activity in platelet-poor plasma is much less potent as compared to that in purified fibrinogen solution. It inhibited ristocetin-induced aggregation of human platelets in a dose-dependent manner in the presence of von Willebrand factor.

Structural domains in venom proteins: evidence that metalloproteinases and nonenzymatic platelet aggregation inhibitors (disintegrins) from snake venoms are derived by proteolysis from a common precursor

A comparison of the structures of a precursor of trigramin (a disintegrin), metalloproteinases, disintegrins and related proteins, suggests the existence of common precursors for metalloproteinases and disintegrins. The proposed common precursor and related proteins have four distinct domains (A-D). Domain B contains the metal binding site and the catalytic Glu residue, which comprise the active site of metalloproteinases. Domain C contains the Arg-Gly-Asp sequence and hence the ability to inhibit the activity of integrins. Domains A and D are unique and their biochemical or biological activity is unknown. The proposed precursor can be proteolytically cleaved at several interdomain sites, releasing the disintegrins and metalloproteinases. A survey of more than 100 venom metalloproteinases and disintegrins strongly supports the existence of precursor proteins and their structural domains. This is also upheld by the co-occurrence occurrence of metalloproteinases and disintegrins in the venoms of several genera of crotalid and viperid snakes. The likelihood of intradomain disulfide bridges, and accessibility of all interdomain cleavage sites also supports our contention. The susceptibility of the cleavage sites appears to be determined by nearby disulfide bridges and glycosylation. Recognition of the proposed structural domains of venom proteinases should help clarify the structure-function relationships of several related proteins, and influence the synthesis of recombinant disintegrins, metalloproteinases and related polypeptides.

Isolation from opossum serum of a metalloproteinase inhibitor homologous to human alpha 1B-glycoprotein

Fractionation of opossum (Didelphis virginiana) serum with (NH4)2SO4, followed by chromatography on DEAE-Sepharose, phenyl-Sepharose, and Mono Q HR 5/5, has resulted in the isolation in homogeneous condition of a metalloproteinase inhibitor designated oprin (opossum proteinase inhibitor). Oprin is a single-chain glycoprotein (26% carbohydrate) with an estimated Mr = 52,000, pI = 3.5, and E(1%/1 cm) = 11. Oprin inhibited snake venom metalloproteinases, but showed no activity on venom serine proteinases or on bacterial metalloproteinases. Incubation of Crotalus atrox alpha-proteinase (EC 3.4.24.1) with oprin, and analysis of the reaction products by chromatography on Mono Q HR 5/5 and by electrophoresis under nondenaturing conditions, indicated formation of an inactive enzyme/inhibitor complex. The complex dissociated during SDS/polyacrylamide gel electrophoresis. An opossum liver cDNA library was immunoscreened, and clones containing cDNA encoding for part of the open reading frame for oprin were isolated. The cDNA inserts contained nucleotide sequences corresponding to two internal amino acid sequences of oprin which had been separately determined by protein sequence analysis. Protein database screening using a 211 amino acid sequence deduced from one of the cDNA inserts showed no significant homology to known proteinase inhibitors. There was, however, a 36% identity with human alpha 1B-glycoprotein, a plasma protein of unknown function related to the immunoglobulin supergene family. In addition, the amino-terminal sequence of oprin showed 46% identity with human alpha 1B-glycoprotein in a 26 amino acid residue overlap.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of the venom from Crotalus molossus nigrescens Gloyd (black tail rattlesnake): isolation of two proteases

The venom from Crotalus molossus nigrescens contains many activities including: hyde powder azure proteinase; N-benzoyl-arginine-ethyl-ester hydrolase; phospholipase; phosphodiesterase; desoxyribonuclease; fibrinogen coagulase; collagenase, fibrinolytic activity, and hemorrhagic factors. The venom, assayed with amounts of venom up to 50 micrograms protein per assay, does not contain acetylcholinesterase, phosphatase, amylase, ribonuclease, tyrosyl-ester hydrolase or hyaluronidase activities. The venom is lethal to mice with an i.p. LD50 of 2.35 mg/kg mouse. Fractionation of soluble venom by Sephadex G-75 separates at least five families of components. Fractions I-III contains all the enzymes, and fraction V have six small peptides. Further separation of fractions II-III on diethyl-amino-ethyl-cellulose columns at pH 8.0 and 8.3 gave pure proteinase E with a mol. wt of 21,390 and the following N-terminal amino acid sequence; Phe-Ala-Lys-Arg-Tyr-Val-Glx-Leu-Val-Ile-Val-Ala. A thrombin-like enzyme with a mol. wt of 75,000 was also purified from this venom by means of affinity and ion exchange chromatographies.

Effect of cobra and viper venoms on alpha 2-macroglobulin activity in human, bovine, and goat sera

Incubation of human serum with cobra or viper venoms (10 micrograms/0.1 ml serum) caused negligible decrease in total protease inhibitory activity whereas alpha 2-macroglobulin activity was reduced by 67.0-82.0% in 16 hr. The action of venoms on MG activity was time dependent. Human alpha 2-macroglobulin activity was reduced to a much greater extent than goat or bovine factors by the venoms. While 25 micrograms venoms/0.1 ml serum caused 60-100% inhibition of human alpha 2-macroglobulin activity, the bovine factor was not affected under similar conditions. Goat alpha 2-macroglobulin was affected to the extent of 0-20%. Evidence is provided to show that venom proteases generate endogenous proteases in situ in human plasma or serum which in turn bind to alpha 2-macroglobulin. The venom-mediated action was abolished by prior dialysis of the serum or its dilution. Ethylenediaminetetraacetate at 10(-3) M concentration also blocked the reaction. While phenylmethylsulfonyl fluoride had no effect, pepstatin in the concentration range 10(-2) to 10(-3) M caused partial inhibition of the venom-mediated inhibition of alpha 2-macroglobulin activity in human serum.

Proteolysis in vitro of low and high density lipoproteins in human plasma by Cerastes cerastes (Egyptian sand viper) venom

Envenomation by snake venoms would be expected to result in proteolysis of plasma proteins as well as of cellular constituents. Incubation of human serum with crude venom from Cerastes cerastes showed that the plasma lipoproteins were a target of this venom. Fractionation of the crude venom by gel filtration revealed that high density lipoprotein (HDL) was susceptible almost exclusively to the highest mol. wt fraction of venom and that proteolysis was due to a metalloprotease. Although HDL was degraded only by this metalloprotease, the low density lipoprotein (LDL) was proteolyzed by both metalloproteases and serine proteases present in several fractions of the venom. Despite extensive degradation, LDL remained intact, as judged by gradient gel electrophoresis. The selectivity of venom fractions may prove useful in the study of lipoprotein structure.

Purification and properties of a proteinase from Vipera lebetina (snake) venom

A proteinase from the venom of Vipera lebetina was purified by chromatography on Sephadex G-100 and CM-cellulose. The purified proteinase was homogeneous on SDS-polyacrylamide gel electrophoresis and consisted of a single chain with molecular weight of 37,000 +/- 1500. The isoelectric point of the proteinase was over 10. The enzyme was active on casein but not on esters and amides of arginine. It split the oxidized insulin B-chain at the peptide bonds of Tyr16-Leu17, Phe24-Phe25 and Phe25-Tyr26, and glucagon at the bonds Tyr10-Ser11, Leu14-Asp15 and Leu26-Met27. The enzyme was inhibited by DFP and PMSF, and partially by soybean trypsin inhibitor, but not with EDTA.

Characterization of a metallo-proteinase from Bothrops asper (terciopelo) snake venom

Metalloproteinase from the venom of Bothrops asper (proteinase G) is a glycoprotein with 1% neutral hexose and 3.5 moles of sialic acid per mole of protein. It hydrolyses a number of protein substrates such as casein, hemoglobin, gelatin and fibrinogen, whose alpha chain is degraded preferentially. The pH optimum of hydrolysis of casein is approximately 9.5. The protease is devoid of hemorraghic, esterolytic and amidolytic activities. The proteolytic activity of the enzyme increases by about 20% in the presence of 0.2 mM Ca2+ and Mg2+. Among the other ions tested, only Cd2+ and Fe2+ markedly decreased its activity. EDTA and cysteine are also strong inhibitors. In the presence of Ca2+ and EDTA, Zn2+ ions restored 50% of the activity. The amino acid composition shows fewer acidic residues than in related proteinases from other snake venoms.

Venom resistance in the hedgehog, Erinaceus europaeus: purification and identification of macroglobulin inhibitors as plasma antihemorrhagic factors

Hedgehog (Erinaceus europaeus) plasma contains factor(s) which neutralize the hemorrhagic activity of European viper (Vipera berus) venom. These antihemorrhagic factor(s) were purified by gel filtration on Sephacryl S-200 and chromatography on Cibacron Blue Sepharose. The macroglobulin fraction obtained was characterized for proteinase inhibiting activity, molecular weight and purity by polyacrylamide gel electrophoresis and immunological cross-reactivity and was found to contain the three macroglobulin proteinase inhibitors--alpha 2-macroglobulin, alpha 2-beta-macroglobulin and beta-macroglobulin. The purified macroglobulins were totally able to neutralize Vipera berus venom hemorrhagic activity, but no distinction between them in this respect was possible.

Purification and characterization of alpha 2-, alpha 2-beta- and beta-macroglobulin inhibitors in the hedgehog, Erinaceus europaeus: beta-macroglobulin identified as the plasma antihemorrhagic factor

Three macroglobulin inhibitors were purified from hedgehog (Erinaceus europaeus) plasma by sequential chromatography on Cibacron Blue Sepharose, Sephacryl S-200 and preparative agarose gel electrophoresis. Each macroglobulin was characterized for proteinase inhibiting activity, molecular weight by polyacrylamide gel electrophoresis (PAGE), subunit size by sodium dodecyl sulfate (SDS)-PAGE, immunological cross-reactivity to other macroglobulins and antihemorrhagic activity against European viper (Vipera berus) venom. Hedgehog alpha 2-macroglobulin is a tetramer (Mr 800,000) composed of identical monomers (Mr 200,000) that inhibits all proteinases tested and is the homologue of human alpha 2-macroglobulin, rat alpha 2-acute phase globulin, dog alpha 1-macroglobulin and swine alpha 2-macroglobulin fast. Hedgehog alpha 2-beta-macroglobulin is a dimer (Mr 450-550,000) composed of identical monomers (Mr 200,000) that inhibits all proteinases tested and appears to be structurally similar to other animal 'half-molecule' macroglobulins. Hedgehog beta-macroglobulin (Mr 700,000) gave subunits of 34,000 and 39,000 after SDS-PAGE and showed cross-reactivity with swine alpha 2-macroglobulin slow. It inhibits all proteinases tested and is the only macroglobulin with antihemorrhagic activity against V. berus venom. This antihemorrhagic activity may be due to beta-macroglobulin's different structure as compared to other macroglobulins, which may make it less susceptible to inactivation by venom proteinases.

Activation by puff adder venom of inactive renin in normal and hypertensive rat plasma

Inactive renin has been studied extensively in human plasma, but in animal plasma its accurate quantification has proved more difficult, due partly to higher activity of plasma protease inhibitors. Such activity in human plasma can be conveniently destroyed by a metalloprotease in Bitis arietans venom, with concommitant release of endogenous enzyme activities, such as plasma kallikrein, that then activate inactive renin. It was therefore of interest to look for inactive renin in rat and rabbit plasma using this approach, so providing, in addition, a comparison for the disparate data of other groups who have used trypsin or acid for activation. In both rat and rabbit plasma the proportion of inactive renin was 62% of total renin, whereas human plasma contained more inactive renin and a higher proportion, 82%. A higher concentration of venom was required for rat (33 ug venom/ml plasma) and rabbit (4 micrograms/ml) than needed for activation, at a similar rate, in human plasma (1 microgram/ml). When applied to studies of rats made hypertensive and hyper-reninaemic by aortic ligation for 5 days, higher total (active + inactive) renin was observed. The proportion of inactive renin, as a percentage of total renin in plasma collected at this time, was, however, found to diminish significantly. In conclusion, puff adder venom activates inactive renin in rat and rabbit plasma and can be used to study physiological changes in inactive renin in such animal plasma.

Inactivation of bovine chymotrypsin by bovine antithrombin III

Less than a stoichiometric amount of bovine chymotrypsin was progressively inactivated by a bovine AT III preparation. The rate of inactivation was not influenced by a synthetic substrate. Since chymotrypsin has low affinity for heparin, the polysaccharide only doubled the inactivation of the enzyme by the AT III preparation. At a low salt concentration, about two-thirds of the chymotrypsin was instantaneously inactivated by the AT III preparation in the presence of heparin. These observations indicate that inactivation of chymotrypsin is due to AT III itself, not to another contaminating inhibitor(s).

Inactivation of human plasma serine proteinase inhibitors (serpins) by limited proteolysis of the reactive site loop with snake venom and bacterial metalloproteinases

Human plasma serine proteinase inhibitors (serpins) gradually lost activity when incubated with catalytic amounts of snake venom or bacterial metalloproteinases. Electrophoretic analyses indicated that antithrombin III, C1-inhibitor, and alpha 2-antiplasmin had been converted by limited proteolysis into modified species which retained inhibitory activity. Further proteolytic attack resulted in the formation of inactivated inhibitors; alpha 1-proteinase inhibitor (alpha 1-antitrypsin) and alpha 1-antichymotrypsin were also enzymatically inactivated, but active intermediates were not detected. Sequence analyses indicated that the initial, noninactivating cleavage occurred in the amino-terminal region of the inhibitors. Inactivation resulted in all cases from the limited proteolysis of a single bond near, but not at, the reactive site bond in the carboxy-terminal region of the inhibitors. The results indicate that the serpins have two regions which are susceptible to limited proteolysis--one near the amino-terminal end and another in the exposed reactive site loop of the inhibitor.

Chemical studies on protease A of Bitis arietans (puff adder) venom

Protease A of Bitis arietans venom is probably a metalloprotease, since it is inhibited by o-phenanthroline and contains 0.77 moles of zinc per mole protein. The enzyme comprises 213 amino acids, including 9 methionine residues and one free sulphydryl group. It contains one polypeptide chain, which is terminated at the carboxyl end by serine. The amino terminal sequence of protease A is: Arg-Ser-Ser-Asp-Pro-Asn-Lys-Tyr-Phe-Asn-Val-Ile-Val-Val-Val-Asp-Asn-Arg- Met-Val-Asn-Tyr-Tyr-Lys-Gly-Glu-Leu-Asn-Lys-Ile-Thr-. Despite difficulties with 'insoluble peptide core' formation, a number of peptides were purified from peptic and tryptic digests of S-derivatized protease A.

Separation of Crotalus atrox (western diamondback rattlesnake) alpha-proteinase from serine proteinase and hemorrhagic factor activities

A method for obtaining Crotalus atrox alpha-proteinase (EC 3.4.24.1) in a pure form has been developed. Fractionation of the crude venom on DEAE-Sepharose, followed by gel filtration on Bio-Gel P-150 and chromatography on CM-Sepharose, yielded an alpha-proteinase preparation which showed a single band on disc and sodium dodecyl sulfate-polyacrylamide gel electrophoresis and had an activity on casein approximately twice that previously reported. The enzyme is a nonglycosylated single-chain polypeptide with a molecular weight of 26,738 and a pI of 8.15. Proteolytic activity on casein, alpha 1-antichymotrypsin, and Cl-inhibitor was abolished by treatment of alpha-proteinase with 1 mM EDTA, but full activity was retained in the presence of 1 mM phenylmethylsulfonyl fluoride. Caseinolytic activity was increased by 33 and 55% in the presence of 10 mM Mg2+ and Ca2+, respectively. Pure alpha-proteinase is devoid of esterolytic activity on H-D-Pro-Phe-Arg-p-nitroanilide (S-2302), benzoyl-L-arginine ethyl ester, and benzoyl-L-tyrosine ethyl ester. The final preparation has no hemorrhagic factor activity.

Enzymatic inactivation of heparin cofactor II by a proteinase (proteinase-1) isolated from Echis carinatus venom

Heparin cofactor II was enzymatically inactivated by incubation with Echis carinatus venom in the presence of calcium. The initial rate of inactivation increased proportionately with the addition of heparin to a final concentration of 50 micrograms/ml. A proteinase, termed proteinase-1, was purified 17.5-fold from the venom which also enzymatically inactivated heparin cofactor II in the presence of calcium. The initial rate of heparin cofactor II inactivation by proteinase-1 was not increased by heparin at concentrations as high as 200 micrograms/ml. Heparin cofactor II was not inactivated by either unfractionated venom or proteinase-1 in the absence of calcium. The results indicate that heparin cofactor II, like antithrombin III, is susceptible to enzymatic inactivation by metalloproteinases in snake venoms.

Purification and partial characterization of a high molecular weight metalloproteinase from the venom of Crotalus adamanteus (eastern diamondback rattlesnake)

Chromatography of Crotalus adamanteus venom on CM-Sepharose, Cibacron Blue-Sepharose and Phenyl-Sepharose, followed by gel filtration on Ultrogel AcA 44, has resulted in the isolation in homogeneous condition of a metalloproteinase active on casein and hide powder azure. The proteinase has an alkaline isoelectric point, and the trivial name proteinase B ('basic proteinase') is suggested to distinguish it from previously characterized C. admanteus metalloproteinases. Proteinase B is a single chain glycoprotein containing one free sulfhydryl group and having a molecular weight of 60,000. Proteinase B was inactivated by treatment with EDTA, but exposure to phenylmethylsulfonyl fluoride had no effect on proteolytic activity. Proteinase B lacked hemorrhagic activity and did not digest chromogenic substrates specific for thrombin, plasmin or plasma kallikrein.

Characterization of mucrotoxin A from the venom of Trimeresurus mucrosquamatus (the Chinese habu snake)

Mucrotoxin A from the venom of Trimeresurus mucrosquamatus was isolated in homogeneous form by a previously published method. Mucrotoxin A did not hydrolyze casein, however, when dimethylcasein was used as a substrate, the toxin cleaved the substrate. This toxin also hydrolyzed the oxidized B chain of insulin and fibrinogen. The sites of cleavage in the oxidized B chain of insulin were identified as Ser(9)-His(10), His(10)-Leu(11), Ala(14)-Leu(15), Leu(15)-Tyr(16) and Tyr(16)-Leu(17). The toxin digested the A alpha chain of fibrinogen first, followed by hydrolysis of the B beta chain. The fact that no fibrin clot formed indicates that the sites of cleavage in the A alpha and B beta chains of fibrinogen by the toxin must be different from those cleaved by thrombin. Mucrotoxin A produced systemic hemorrhage in internal organs such as the heart and stomach.

Enzymatic digestion of human plasma inter-alpha-trypsin inhibitor by snake venom metalloproteinases

Incubation of human plasma inter-alpha-trypsin inhibitor with crotalid, viperid, colubrid or elapid venoms resulted in random cleavage of the intact inhibitor (200,000 mol. wt) and formation of inhibitor of 130,000, 77,000, 58,000, and 38,000 mol. wt, along with several minor products. The overall patterns of digestion varied among the venoms studied. However, a 77,000 mol. wt inhibitor cleavage product was formed by all venoms tested, and this fragment was resistant to proteolysis even after a 24 hr incubation with the venoms. Venom pre-treated with phenylmethylsulfonyl fluoride digested inter-alpha-trypsin inhibitor; however, pre-treatment with EDTA completely stopped the reaction, indicating that venom metalloproteinases were responsible for the inhibitor digestion. The inhibitor cleavage products retained the ability to inhibit trypsin, but had no inhibitory activity against venom proteinases.

Purification and partial characterization of the hemorrhagic factor from the venom of Crotalus adamanteus (eastern diamondback rattlesnake)

A proteinase from Crotalus adamanteus venom has been isolated to the stage of electrophoretic homogeneity by chromatography of the crude venom on CM-Sepharose, Phenyl-Sepharose, Ultrogel AcA 44 and DEAE-Sepharose. The proteinase accounts for 100% of the detectable hemorrhagic activity in the venom, and the name C. adamanteus proteinase H is suggested. Proteinase H is a single chain glycoprotein with a molecular weight of 85,700. Proteinase H is active on casein and hide powder azure, but does not digest benzoyl-L-arginine ethyl ester or benzoyl-L-tyrosine ethyl ester. Proteolytic and hemorrhagic activity were both abolished by treatment with EDTA and neither activity was restored by prolonged dialysis against Zn2+ or Ca2+. However, both activities were retained after treatment with phenylmethylsulfonyl fluoride. A minimal hemorrhagic response was elicited in mice by s.c. injection of 0.1 microgram of proteinase H. The caseinolytic activity of proteinase H was not inhibited during incubation with human alpha 2-macroglobulin, nor was the inhibitor inactivated by proteinase H.

Enzymatic inactivation of human plasma C1-inhibitor and alpha 1-antichymotrypsin by Pseudomonas aeruginosa proteinase and elastase

Two major human plasma proteinase inhibitors, C1-inhibitor and alpha 1-antichymotrypsin, were enzymatically inactivated by Pseudomonas aeruginosa elastase and proteinase. Incubation of C1-inhibitor with the Pseudomonas enzymes at inhibitor/enzyme molar ratios of 1000:1 (elastase) or 22:1 (proteinase) resulted in cleavage of the 104 kDa intact inhibitor to an 89 kDa intermediate which retained full inhibitory activity against plasmin and plasma kallikrein. The intermediate was then cleaved to an 83 kDa inactive product. The initial non-inactivating cleavage of C1-inhibitor occurred in a region of the molecule readily accessible to limited proteolysis by both enzymes. The inactivating cleavage, however, occurred more readily with the elastase. alpha 1-Antichymotrypsin was inactivated by P. aeruginosa proteinase and elastase by limited proteolysis at inhibitor/enzyme molar ratios of 14 000:1. The 64 kDa intact inhibitor was cleaved to form an inactive 60 kDa product, and a low molecular mass peptide fragment was observed. No stable enzyme-inhibitor complexes were detected, and no random proteolysis of the inactivated inhibitors was noted, even after prolonged incubation. Catalytic inactivation of C1-inhibitor and alpha 1-antichymotrypsin by P. aeruginosa proteinase and elastase may contribute to the tissue damage and hemorrhagic lesions which occur during pseudomonal infections.

Anticoagulant proteases from western diamondback rattlesnake (Crotalus atrox) venom

Crotalus atrox venom contains agents that render human fibrinogen and plasma incoagulable by thrombin. To elucidate the mechanism of alteration of fibrinogen clotting function by the venom, four immunochemically different proteases, I, II, III, and IV, were purified from the venom by anion-exchange chromatography and column gel filtration. All four proteases had anticoagulant activity rendering purified fibrinogen incoagulable. Proteases I and IV do not affect fibrinogen in plasma but in purified fibrinogen cleave the A alpha chain first and then the B beta and gamma chains. Both enzymes are metalloproteases containing a single polypeptide chain with 1 mol of zinc, are inhibited by (ethylenedinitrilo)tetraacetate and human alpha 2-macroglobulin, and have an optimal temperature of 37 degrees C and an optimal pH of 7. Protease I has a molecular weight (Mr) of 20 000 and is the most cationic. Protease IV has an Mr of 46 000 and is the most anionic glycoprotein with one free sulfhydryl group. Proteases II and III degrade both purified fibrinogen and fibrinogen in plasma, cleaving only the B beta chain and leaving the A alpha and gamma chains intact. Both enzymes are alkaline serine proteases, cleave chromogenic substrates at the COOH terminal of arginine or lysine, are inhibited by diisopropyl fluorophosphate and phenylmethanesulfonyl fluoride, and have an optimal temperature of 50-65 degrees C. Protease II is a single polypeptide chain glycoprotein with an Mr of 31 000. Protease III is a two polypeptide chain protein with an Mr of 24 000, each of the two chains having an Mr of 13 000; its activity is not affected by major protease inhibitors of human plasma. Proteases II and III are enzymes with unique and limited substrate specificity by cleaving only the B beta chain, releasing a peptide of Mr 5000 and generating a fibrinogen derivative of Mr 325 000, with intact A alpha and gamma chains and poor coagulability. Since the two enzymes are active in human plasma and serum, it is postulated that proteases II and III can mediate anticoagulant effects in vivo after envenomation.

Characterization of hemorrhagic principles from Trimeresurus gramineus snake venom

In addition to alpha-fibrinogenase (hemorrhagin I, HR1), a potent hemorrhagic principle (hemorrhagin II, HR2) was purified from Trimeresurus gramineus venom. It was homogeneous as judged by SDS-polyacrylamide gel electrophoresis. HR2 was a single peptide chain containing 10% carbohydrate with a molecular weight of 81,500. It possessed 669 amino acid residues per molecule, while HR1 contained only 203 amino acid residues per molecule with a molecular weight of 23,500. Both hemorrhagins possessed proteolytic activities toward fibrinogen, casein and azocoll. However, the proteolytic activities of HR1 were much more potent than those of HR2. They were devoid of TAME-esterase and phospholipase A2 activities which were found in crude venom. beta-Mercaptoethanol and antivenin completely inhibited the hemorrhagic activities of HR1 and HR2, while epsilon-aminocaproic acid, trasylol, p-bromophenacyl bromide, phenylmethanesulfonyl fluoride and soybean trypsin inhibitor did not. EDTA completely inhibited the hemorrhagic, fibrinogenolytic and caseinolytic activities of HR1. EDTA also completely inhibited the caseinolytic and fibrinogenolytic activities of HR2, but only partially inhibited its hemorrhagic activity. Subsequent addition of Zn2+ (5 mM) reversed the EDTA-induced inhibitory effect on the hemorrhagic activity of HR1. However, ZN2+ did not reverse the EDTA-induced inhibitory effect on the HR2-induced hemorrhagic activity. These hemorrhagins were found to be ZN2+-containing metalloproteinases. Therefore, the hemorrhagic activity of HR1 seems to be related to its proteolytic activity while that of HR2 seems to be unrelated to its proteolytic activity.

Resistance of a hemorrhagic proteinase from timber rattlesnake venom to proteolytic degradation

The proteolytic activity of hemorrhagic proteinase IV isolated from timber rattlesnake (Crotalus horridus horridus) venom was resistant to inactivation by trypsin, pronase and the proteolytic IIt fraction isolated from timber rattlesnake venom. SDS-polyacrylamide gel electrophoresis of the hemorrhagin incubated alone and with the three proteinases revealed that the addition of trypsin or the IIt fraction caused little apparent degradation of the hemorrhagin, whether or not the samples were reduced prior to electrophoresis. SDS electrophoresis of the hemorrhagin after incubation with pronase revealed a single band of 28,000 apparent molecular weight (as compared to 52,000 for the original hemorrhagin) if the samples were not reduced prior to electrophoresis, and a single band of 17,000 if reduced. If the hemorrhagin was reduced and alkylated, it was much more susceptible to hydrolysis by all three proteinases.

Protease inhibitors in serum and urine of snakebite victims

In victims of poisonous snakebites, serum total antichymotryptic activity but not the antitryptic activity was found to be increased. In addition, urinary antitryptic activity was found to be markedly elevated. In nonpoisonous snakebite cases, no such differences were noted. Ion-exchange chromatographic analysis of serum protease inhibitors revealed the absence of inhibitory activity in the alpha 2-macroglobulin fraction and elevation of alpha 1-antichymotrypsin in poisonous bite cases. In addition, there was a significant increase in the ratio of cationic to anionic fraction of alpha 1-protease inhibitor compared to normals. Urinary antitryptic activity could serve as a reliable index in assessing clinical improvement in snakebite victims during treatment and in differentiating poisonous from nonpoisonous cases.

Analysis of the effects of snake venom proteinases on the activity of human plasma C1 esterase inhibitor, alpha 1-antichymotrypsin and alpha 2-antiplasmin

Incubation of C1 esterase inhibitor with Crotalid, Viperid and Colubrid snake venoms resulted in enzymatic inactivation of the inhibitor. Intact inhibitor (104 kDa) was converted into an active intermediate species of 89 kDa and then a further cleavage resulted in formation of an 86-kDa inactive inhibitor. In contrast, C1 esterase inhibitor did not lose activity during incubation with Elapid venoms; however, the intact inhibitor was gradually converted to an active species of 89 kDa during the incubation. Human alpha 1-antichymotrypsin was inactivated by all venoms tested, including those from the Elapid family. The 67-kDa intact inhibitor was converted by the venom proteinases to an inactive 63-kDa form. The results suggest that this acute-phase plasma protein is readily susceptible to inactivation by venom proteinases. Human alpha 2-antiplasmin (68 kDa) was cleaved to form a 61-kDa active intermediate, which then underwent a second cleavage to produce an inactive 53-kDa product. Elapid venoms had no effect on alpha 2-antiplasmin activity and did not cleave this inhibitor. All inhibitors were inactivated with catalytic amounts of venom proteinases. No stable proteinase-proteinase inhibitor complexes were detected, and no random proteolysis of the inhibitors occurred.

Isolation and characterization of a hemorrhagic proteinase from timber rattlesnake venom

A protein isolated from timber rattlesnake (Crotalus horridus horridus) venom by ion-exchange and high-pressure liquid chromatography is hemorrhage inducing and lethal to mice (LD50 of 10 micrograms/g of body weight). It is a Ca2+- and Zn2+-containing proteinase and has the ability to hydrolyze hide powder azure. Atomic absorption spectroscopy shows 2.5 Ca2+ and 1 Zn2+ per protein monomer. The proteinase activity is destroyed by incubation with disulfide-reducing agents and by dialysis against ethylenediaminetetraacetate. Coincident with the loss of proteinase activity is a corresponding loss of lethal and hemorrhagic activities, suggesting that all three are related. Attempts to replace the metals and restore activity have been unsuccessful. Amino acid analysis and isoelectric focusing reveal that this component is an acidic protein (pI = 5.1) containing about 20 disulfide bonds and 507 residues. Reduction of one disulfide bond per molecule decreases proteinase activity by 50% while reduction of eight disulfide bonds decreases activity by 80%. Loss of hemorrhagic activity parallels the decrease in proteinase activity.

Isolation and characterization of a proteolytic enzyme from the venom of the snake Bothrops jararaca (Jararaca)

Bothropasin, one of the proteases from the venom of Bothrops jararaca active on casein, was isolated by ammonium sulfate precipitation, DEAE-cellulose and DEAE-Sephadex A-50 chromatographies and Sephadex G-100 column filtration. The preparation possessed no other detectable activities which are present in the crude venom. Addition of Ca2+ during purification stabilized the enzyme. The endopeptidase was inhibited by EDTA and EGTA; Ca2+ did not restore the activity of the inhibited enzyme. The material was homogeneous by polyacrylamide gel electrophoreses at different pH values, immunoprecipitation and crossed immunoelectrophoresis. By SDS-polyacrylamide gel electrophoresis the denatured and reduced enzyme had only a 48,000 molecular weight band. In the presence of 6 M guanidine-HCl and 0.1 M beta-mercaptoethanol the preparation showed a value of 49,870 by sedimentation equilibrium. The native tertiary structure of the protein is dependent on S-S and metal bonds. The denatured and reduced enzyme, in the presence of EDTA, showed a molecular weight of 37,300 by sedimentation equilibrium, a value which was also confirmed in SDS-polyacrylamide gel electrophoresis. The enzyme hydrolyzed five peptide bonds: His-Leu (5-6), His-Leu(10-11), Ala-Leu(14-15), Tyr-Leu(16-17) and Phe-Phe(24-25) in the B-chain of oxidized insulin.