Purification, characterization and crystallization of a group of earthworm fibrinolytic enzymes from Eisenia fetida

Seven fibrinolytic enzymes were purified from the earthworm Eisenia fetida. The molecular weights of the enzymes were 24663, 29516, 29690, 24201, 24170, 23028 and 29595, and the respective isoelectric points were 3.46, 3.5, 3.5, 3.68, 3.62, 3.94 and 3.46. All the proteases showed different fibrinolytic activity on fibrin plates. Studies on substrate specificity and inhibition indicated that they belonged to different types of serine proteases. N-Terminal sequencing indicated their high homology to those from the earthworm Lumbricus rubellus. All the enzymes have been crystallized.

Isolation and some characterizations of a glycosylated fibrinolytic enzyme of earthworm, Eisenia fetida

Resin coupled with m-aminophenylbornic acid was used to isolate a glycosylated component from homogenate of earthworm (Eisenia fetida). The fraction showed a single band on SDS-PAGE with a molecular weight of 34, 193 Da determined by mass spectroscopy. The N-terminal region is AQVCCPDI, different from those of earthworm fibrinolytic enzymes reported previously (Nakajima et al. 1993). This glycosylated component showed an activity on digesting both Chromozym-TH and fibrin, suggesting that it is a novel fibrinolytic enzyme.

A novel class of small functional peptides that bind and inhibit human alpha-thrombin isolated by mRNA display

Here we report the in vitro selection of novel small peptide motifs that bind to human alpha-thrombin. We have applied mRNA display to select for thrombin binding peptides from an unbiased library of 1.2 x 10(11) different 35-mer peptides, each containing a random sequence of 15 amino acids. Two clones showed binding affinities ranging from 166 to 520 nM. A conserved motif of four amino acids, DPGR, was identified. Clot formation of human plasma is inhibited by the selected clones, and they downregulate the thrombin-mediated activation of protein C. The identified peptide motifs do not share primary sequence similarities to any of the known natural thrombin binding motifs. As new inhibitors for human thrombin open interesting possibilities in thrombosis research, our newly identified peptides may provide further insights into this field of investigation and may be possible candidates for the development of new anti-thrombotic agents.

[Isolation and identification of proteins with anti-tumor and fibrinolysogen kinase activities from Eisenia foetida]

Proteins from Eisenia foetida possess many biological activities. A group of proteins precipitated by ethanol were isolated and purified by Sephadex G-75 and HiPrep 16/60 DEAE columns, then identified by one- or two- dimensional electrophoresis and mass spectrometry. 2D gel experiments displayed that the pI of proteins from Eisenia foetida were mainly from 3.0 to 4.0. Anti-tumor and kinase activities were determined by in vitro experiments. The enthanol fraction D2(8) showed both of the activities. These ethanol-precipitated proteins were identified further by native polyacrylamide electrophoresis, the protein spots were cut off from gels and digested by trypsin, the peptide mass fingerprints (PMFs) were determined by mass spectrometry. PMF, molecular weight, amino acid composition and N-terminus of 6 proteins were characterized, and band 9 was identified as D2(8). The results suggested that there exist proteins in Eisenia foetida possessed both anti-tumor and fibrinolysogen kinase activities. These methods can be used for identification of the natural bioactive proteins.

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

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

Efficient expression and secretion of recombinant hirudin III in E. coli using the L-asparaginase II signal sequence

One of the hirudin variants HV3 was efficiently expressed in Escherichia coli using the L-asparaginase II signal sequence and the product was secreted into the culture medium. For the secretory manufacture of HV3, the L-asparaginase II signal sequence containing a single NheI restriction site at its 3' end was designed using the degenerate codons and PCR-amplified from E. coli chromosomal DNA. The synthetic HV3 coding sequence was fused to the signal sequence in-frame by its 5' NheI restriction site. The above signal-HV3 fusion gene was inserted into an expression vector pTA, which was derived from pkk223-3 such that its expression was under the control of the tac promotor. The resulting HV3 secretion expression vector pTASH thus constructed was introduced into an E. coli host cell AS1.357 with high L-asparaginase II producing level. After inducing with IPTG, the expression product was efficiently secreted into the culture medium and shake-flask culturing gave a yield of approximately 5 x 10(5)ATU/L (approximately 60mg/L). The secreted HV3 was easily purified from culture supernatant using ultrafiltration, ion-exchange column chromatography, and FPLC reverse-phase chromatography. The purified rHV3 from the culture supernatant had the expected N-terminal amino sequence and strong antithrombin activity, suggesting that the signal sequence was completely removed and the product was processed accurately during the secretion process.

Antithrombin activity of medicinal plants from central Florida

A chromogenic bioassay was utilized to determine the antithrombin activity of methylene chloride and methanol extracts prepared from 30 plants of central Florida. Extracts of Ardisia crenata, Tetrapanax papyriferus, Lagerstroemia indica, Callistemon lanceolatus, Antigonon Leptopus, Magnolia virginiana, and Myrica cerifera demonstrated activity of 80% or higher in this bioassay system.

D-003, a potential antithrombotic compound isolated from sugar cane wax with effects on arachidonic acid metabolites

D-003 is a natural mixture of higher primary saturated aliphatic acids purified from sugar cane wax, whose main component is octacosanoic acid followed by triacontanoic, dotriacontanoic, and tetratriacontanoic acids. D-003 inhibits platelet aggregation and arterial thrombosis experimentally induced in a dose-dependent fashion. This study was undertaken to investigate the effects of D-003 (25 and 200 mg/kg) in experimental models of venous thrombosis and on plasma levels of two metabolites from arachidonic acid (AA) : thromboxane A(2) (TxA(2)) and prostacyclin (PgI(2)). D-003 orally administered as single doses of 200 mg/kg, but not at 25 mg/kg, significantly increased plasma levels of 6 keto PgF1alpha levels, a stable metabolite of PgI(2) in PPP obtained from collagen-stimulated blood (4 microg/ml) compared with control group. Nevertheless, levels of 6 keto PgF1alpha levels determined after 10 days of oral treatment with both doses of D-003 were significantly larger than those of the controls. Likewise, single and repeated oral doses of D-003 (25 and 200 g/kg) significantly reduced the TxB(2) and MDA plasma levels obtained from whole blood stimulated by collagen. Hence, TxB(2)/6 keto PgF1alpha ratio significantly decreased in animals treated with D-003. Single and repeated oral doses of D-003 (25 and 200 mg/kg) significantly reduced the weight of venous thrombus experimentally induced in rats. D-003 at single doses (400 mg/kg but not 200 mg/kg) significantly protected from death induced by endovenous infusion of collagen plus epinephrine in mice. The present results support that these effects of D-003 on AA metabolites could explain, at least partially, its antiplatelet and antithrombotic effects.

[Experimental study on anti-thrombus effect of different extracts from Semen Persicae]

OBJECTIVE

To observe the effects of anti-thrombus of different extracts from Semen Persicae and provide experimental basis for finding and defining effective fraction of Semen Persicae.

METHODS

The effects of different extracts from Semen Persicae on clotting time in mice, pulmonary embolism in mice and electro-irritate thrombosis in rats were observed.

RESULT

Ethyl acetate extract from Semen Persicae could prolong clotting time in mice, markedly relieve respiratory difficult due to pulmonary embolism in mice induced by ADP-Na, obviously retard the generation of thrombosis induced by electrical injury of carotid artery in rats.

CONCLUSION

Ethyl acetate extract from Semen Persicae possesses evidently anti-thrombotic effect.

Effect of earthworm (G-90) extract on formation and lysis of clots originated from venous blood of dogs with cardiopathies and with malignant tumors

The stability of homeostasis is important to keep a balance between coagulation and fibrinolysis. A disorder of homeostasis leads to different physiological changes and causes different diseases such as cardiopathies and malignant tumors. Cardiopathies is characterized by a hypercoagulation. In the malignant tumors, besides the hypercoagulation due to plasminogen activators (PA) formed inside the tumor, a disorder of homeostasis leads also to acceleration of the fibrinolysis. The variety of internal and external factors in both cases determine the deviation of time for the clots formation, as well as the lyses of blood and fibrin clots. In this study the venous blood as well as the blood and the fibrin clots, derived from healthy dogs, the dogs with cardiopathies and with malignant tumors, were examined for the time of coagulation and fibrinolysis by adding different substances. In these experiments we used a glycolipoprotein extract from earthworm tissue homogenate (G-90) and the proteolytic enzymes P I and P II, isolated from G-90. The efficacy of the tested substances was comparable with the clinically administered anticoagulants. The most significant differences in clotting time among the three tested groups of dogs were obtained by application of the original G-90. The results suggest a possibility that G-90, along with the fibrinolytic enzymes and other biologically active factors, also contains a factor that decelerates the formation of clot in a specific medium, such as the blood from the dogs with malignant tumors.

Purification and characterisation of two hemorrhagic metalloproteinases from the venom of the long-nosed viper, Vipera ammodytes ammodytes

Two hemorrhagic proteins, VaH1 and VaH2, have been purified from Vipera ammodytes ammodytes venom. They are monomeric glycoproteins of an apparent molecular mass of 70kDa and multiple isoelectric points around pH 5.5. Both molecules are proteolytically active against azocasein as substrate. VaH1, which was characterised in detail, showed maximum activity at pH 7.5. Ethylenediaminetetraacetic acid eliminated the proteolytic as well as the hemorrhagic activity of VaH1 while iodoacetamide, phenylmethylsulfonyl fluoride and pepstatin A, inhibitors of cysteine, serine and aspartic proteinases respectively, had no effect. VaH1 is therefore a metalloproteinase whose hemorrhagic activity is very likely the result of its proteolytic activity. VaH1 is a fibrinogenase, hydrolysing exclusively the Aalpha-chain of fibrinogen. In the B-chain of insulin it cleaved with a high preference the bond between Ala(14) and Leu(15). Based on its molecular mass, VaH1 (as well as VaH2) is a Class P-III metalloproteinase. Partial amino acid sequences of its CNBr fragments demonstrated a high level of identity with the reprolysin subfamily of zinc-metalloproteinases.

Isolation of endogenous anticoagulant N-sulfated glycosaminoglycans in human plasma from healthy subjects

Endogenous N-sulfated glycosaminoglycans (GAGs) comigrating with standard heparin and sensitive to nitrous acid treatment were isolated from plasma of healthy donors. The amount of these compounds was 7-10 microg/ml, and activated partial thromboplastin time, anti-Xa and anti-IIa activities were similar to those of standard heparin of high molecular mass. Analysis with gradient PAGE of the putative endogenous heparin showed a mean molecular mass of 12 kD. These N-sulfated GAGs could be isolated only after removal of binding peptides that impaired purification by ion-exchange chromatography. We used SDS-PAGE as a tool to separate peptides from endogenous GAGs. N-sulfated GAGs exited the gel before peptides when the electrophoresis was overrun. Endogenous GAGs could be recovered by ion-exchange chromatography of the SDS-PAGE buffer, 'free' from associating peptides. These results strongly support the hypothesis that endogenous heparin is associated in vitro with a variety of proteins and that this association could be responsible for modification of both heparin and protein activities.

Current status of the anticoagulant hirudin: its biotechnological production and clinical practice

Hirudin is a potent thrombin inhibitor originally derived from the medicinal leech, Hirudo medicinalis. Owing to its high affinity and specificity for thrombin, hirudin has been intensively investigated for research and therapeutic purposes. The investigation of hirudin has contributed greatly to the understanding of the mode of action of thrombin and the clotting system. Hirudin and several hirudin analogues have also been demonstrated to have several advantages as a highly specific anticoagulant over the most widely used drug, heparin. Due to the great demand for hirudin in physicochemical and clinical studies, various recombinant systems have been developed, using bacteria, yeasts, and higher eukaryotes, to obtain the biologically active hirudin in significant quantities. After 10 years of clinical applications, two recombinant hirudins and a hirudin analogue have gained marketing approval from the United States Food and Drug Administration, for several applications. Clinical trials are currently ongoing for other treatments for thrombotic disease. As a consequence, it is conceivable that hirudin may expand its therapeutic utility over heparin in the near future.

Dual effects of sulfated D-galactans from the red algae Botryocladia occidentalis preventing thrombosis and inducing platelet aggregation

Sulfated D-galactans occur on the red algae Botryocladia occidentalis as three fractions that differ in their sulfate content. Fractions F2 and F3 are potent anticoagulants. Like heparin, they enhance thrombin and factor Xa inhibition by antithrombin and/or heparin cofactor II. The inhibition potency increases simultaneously with the sulfate content of the fractions. The antithrombotic activity of these sulfated D-galactans was investigated on an experimental thrombosis model in which thrombus formation was induced by a combination of stasis and hypercoagulability. In contrast with heparin. the sulfated D-galactans showed a dual dose-response curve preventing thrombosis at doses up to approximately 0.5 mg/ kg body weight but losing the effect at higher doses. This unexpected behavior is probably due to a combined action of the sulfated D-galactan as anticoagulant and also as a strong inducer of platelet aggregation. In platelet-depleted animals the antithrombotic activity at higher dose of sulfated D-galactan is restored and almost total inhibition of thrombus formation is achieved. The sulfated D-galactan has no hemorrhagic effect even at high doses, possibly as a consequence of its effect on platelet aggregation. At comparable dose heparin has an intense bleeding effect. These results indicate that new polysaccharides, with well-defined structures, can help to distinguish events, such as antithrombotic and anticoagulant activities, bleeding and platelet-aggregating effects, which are obscure when induced simultaneously by a single compound.

Crotalin, a vWF and GP Ib cleaving metalloproteinase from venom of Crotalus atrox

Binding of von Willebrand factor (vWF) to a variety of extracellular matrix (ECM) components and to platelet glycoprotein (GP) Ib-IX-V complex is important in mediating platelet adhesion and aggregation in the early stage of hemostasis. We previously purified a potent antithrombotic protein, named crotalin, functionally acting as a GP lb antagonist (1). In this study, we further characterized crotalin as a P-I metalloproteinase with a molecular mass of 25 kDa as determined by gel filtration and two-dimensional SDS-PAGE. Crotalin is a vWF binding and cleaving metalloproteinase. In addition, crotalin cleaved platelet GP lb as judged by flow cytometry and Western blotting. The multiple effects of crotalin on vWF and platelet GP lb antagonized ristocetin-, but not collagen and thrombin-induced platelet aggregation, suggesting that its effect is specific. We also found that crotalin autoproteolytically degraded to approximately 14 and approximately 10 kDa fragments in the presence of SDS. Interestingly, both degradation fragments, intact and reduced crotalin were able to bind vWF, suggesting the binding of crotalin to vWF is conformation-independent. In conclusion, the results presented further explain the potent antithrombotic effect of crotalin in vivo. In addition, the multiple effects of crotalin may be used as a tool to determine the binding motifs that are responsible for the vWF-ECMs or vWF-GP lb interaction.

A novel tetrameric venom protein, agglucetin from Agkistrodon acutus, acts as a glycoprotein Ib agonist

A novel platelet agglutination inducer, agglucetin, was purified from the Formosan Agkistrodon acutus snake venom. It migrated as a single band with an apparent molecular mass of 58.8 kDa and two distinct bands of 16.2/14.5 kDa under non-reducing and reducing conditions by SDS-PAGE, respectively. Further confirmed by FPLC, electrospray ionization mass spectrometry and 2D-PAGE, native agglucetin exists as a tetramer composed of disulfide-linked alpha1, alpha2, beta1 and beta2 subunits. Partial N-terminal sequence of agglucetin subunit showed a high degree of homology to those of C-type lectin-like glycoprotein (GP) Ib binding proteins. Functional studies showed that agglucetin. in the absence of von Willebrand factor (vWF), dose-dependently induced platelet agglutination and caused a negligible elevation of intracellular Ca+2 mobilization and thromboxane B, formation in human platelet suspensions. Anti-GP Ib monoclonal antibodies (mAbs), AP1 or LJ-Ib1, specifically inhibited agglucetin-induced platelet agglutination in a dose-dependent manner. However, EDTA, arietin (a long chain RGD-containing disintegrin), 7E3 (an anti-GP IIb/IIIa mAb), heparin, hirudin, PGE1, or indomethacin exhibited no inhibitory effect on agglucetin-induced platelet agglutination. Furthermore, flow cytometric analysis revealed that FITC-agglucetin dose-dependently bound to human formalin-fixed platelets in a saturable manner, and its binding was specifically blocked by anti-GP Ib mAb. It is concluded that agglucetin, acts specifically on an epitope of platelet membrane GP Ib overlapping with that of API, causing platelet agglutination in a Ca+2- and GP IIb/IIIa-independent manner.

[Isolation, purification, and separation of the complex preparation of extracellular proteinases with fibrinolytic and anticoagulant properties from Aspergillus ochraceus 513]

The extracellular proteinase complex of the microscopic fungus Aspergillus ochraceus 513 was isolated, purified, and separated by affinity chromatography on bacillichin-silochrom and subsequent column chromatography on DEAE-Toyopearl 650 M. The extracellular enzyme of the protein C activator type had a molecular mass of 36.5 kDa and activity close to that of the Agkistrodon snake venom protein C activator. The fibrinolytic and anticoagulant activities of the enzyme were investigated.

Some features of intestinal absorption of intact fibrinolytic enzyme III-1 from Lumbricus rubellus

In order to investigate whether earthworm fibrinolytic enzyme III-1 (EFE-III-1) isolated from Lumbricus rubellus is capable of transporting into blood through intestinal epithelium and keeping its biological function in circulation, we have raised an antibody against EFE-III-1. The immunological results showed that 10-15% of intact EFE-III-1 was absorbed by the intestinal epithelium with the incubation chamber method [Vilhardt and Lundin, Acta Physiol. Scand. 126 (1986) 601-607]. The enzyme could be detected in the intestinal epithelial cells by immunohistochemistry. Furthermore, immunoreactive intact EFE-III-1 was found in serum or plasma after intraperitoneal injection of rats. Approx. 10% of the full-size enzyme could transport through the intestinal epithelium. The maximum remaining activity in blood could be assayed around 60 min after the intraperitoneal injection.

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.

Biochemical characterization of a thrombin-like enzyme and a fibrinolytic serine protease from snake (Agkistrodon saxatilis) venom

A thrombin-like enzyme and a fibrinolytic serine protease were purified to homogeneity from the venom of a Korean snake Agkistrodon saxatilis emelianov. Both the purified enzymes migrated as a single protein band corresponding to 39 kDa in SDS-PAGE. However, the molecular mass was reduced to 28 kDa by enzymatic removal of the N-linked carbohydrates in those two different enzyme species. Although the thrombin-like enzyme and the fibrinolytic protease show homologous features in their molecular sizes and N-terminal amino acid sequences, yet they can be clearly distinguished from each other in terms of substrate specificity, susceptibility to inhibitors and fibrinogen degradation. It is postulated that these two enzymes are capable of functioning in a cooperative manner to effectively remove fibrinogen and consequently to reduce the blood viscosity.

Defibrinogenating enzymes

The venoms from 3 snakes have been shown to induce defibrinogenation: ancrod from the venom of Calloselasma rhodostoma (formerly known as Agkistrodon rhodostoma), batroxobin from the venom of Bothrops atrox moojeni, and crotalase from the venom of Crotalus adamanteus. The purified fractions of ancrod, batroxobin, and crotalase possess coagulant, proteolytic and esterolytic properties, although their primary mechanism of action is a proteolytic effect on circulating fibrinogen. Ancrod cleaves only the A-fibrinopeptides, but not the B-fibrinopeptides, from fibrinogen; this contrasts with thrombin, batroxobin and crotalase, which cleave both fibrinopeptides A and B. Within minutes of administration of ancrod or batroxobin, there is a significant reduction in plasma fibrinogen levels, and these remain exceedingly low with repeated administration (once or twice daily). The rapid fall in plasma fibrinogen levels is accompanied by a slightly delayed but marked rise in the level of fibrinogen-fibrin degradation products. Plasminogen levels are decreased and blood viscosity is reduced, but formed elements in the circulating blood remain unaltered. Ancrod and batroxobin have been investigated in patients with stroke, deep-vein thrombosis, myocardial infarction, peripheral arterial thrombosis, priapism, and sickle-cell crisis; crotalase has not been administered to humans. However, results have been difficult to interpret, and additional well designed trials are needed to better define the optimum role of ancrod and batroxobin in the management of these conditions. Overall, treatment is well tolerated and serious adverse events are infrequent. In the coagulation laboratory, ancrod, batroxobin and crotalase may be used as reagents to perform coagulation studies on specimens of blood that contain heparin. These venom fractions can be substituted for thrombin in performing the thrombin time and in removing fibrinogen from plasma for accurate determination of fibrinogen-fibrin degradation products.

Potent fibrinolytic enzyme from a thermophilic Streptomyces megasporus strain SD5

As a therapeutic agent in thrombosis the fibrinolytic enzymes are of interest and the search for a new enzyme continues. A strong fibrin-specific fibrinolytic enzyme was purified from the cell-free spent broth of thermophilic Streptomyces megasporus strain SD5. The crude enzyme was concentrated using ammonium sulphate, dialysis and lyophilization. Approximately 0.11 mg ml(-1) crude enzyme with a specific activity of 4.2 U microg(-1) was obtained. Post-electrophoretic reactivity revealed a monomeric form of the enzyme with a molecular weight of 35 kDa. The optimum pH and temperature for production of the enzyme were 8 and 55 degrees C, respectively. The enzyme was resistant to a broad range of pH ranging from 6 to 9 and temperature ranging from 37 to 60 degrees C. The enzyme was a chymotrypsin-like serine peptidase and the activity of the enzyme was N-terminal-dependent. The in vitro clot lysis by the enzyme at 37 degrees C was encouraging.

Amino acid sequence of VlF: identification in the C-terminal domain of residues common to non-hemorrhagic metalloproteinases from snake venoms

The complete amino acid sequence of a non-hemorrhagic fibrino(geno)lytic enzyme (VlF) isolated from Vipera lebetina venom has been determined. VlF was subjected to separate enzymatic and chemical digestions. Resulting fragments were purified by RP-HPLC and subjected for sequencing by automated Edman degradation. The amino terminus of VlF was determined by mass spectrometry. VlF was shown to be composed of 202 residues having a relative molecular mass of 22,826 Da and containing a zinc-binding site and a catalytically active residue. It displayed significant sequence similarities with many other mature metalloproteinases reported from snake venoms. Sequence comparison of hemorrhagic and non-hemorrhagic mature metalloproteinases revealed the presence at the C-terminal part of the enzymes of two residues common to only hemorrhagic metalloproteinases and two others shared by only non-hemorrhagic ones.

Fluorescent studies on the binding-Ca2 + in fibrinolytic principle separated from snake venom

By using equilibrium dialysis, atomic absorption spectrometry, fluorescence titration and determination of fluorescence lifetime, it can be determined that each fibrinolytic principle (FP) molecule contains one Ca2+-binding site and one Ca2+ ion, which can be substituted by a Tb3+ ion completely. The intramolecular energy transfer between Tb3+ and the tryptophan (Trp) residue in FP has been investigated through fluorescence spectroscopy. In the FP molecule, the excited energy can transfer from the Trp residue as an energy donor to the Tb3+ ion substituted as an acceptor. The distance between Tb3+ and the Trp residue, approximately 0.38 nm, has been calculated with the experimental data and Forster theory.