Production and biochemical and biophysical characterization of fibrinolytic protease of a Mucor subtilissimus strain isolated from the caatinga biome.

Cardiovascular diseases, resulting from the deposition of clots in blood vessels, are the leading cause of death worldwide. Fibrinolytic enzymatic activity can catalyze blood clot degradation. Findings show that 36 fungal isolates recovered from Caatinga soils have the potential to produce fibrinolytic protease under submerged conditions. About 58 % of the isolates displayed fibrinolytic activity above 100 U/mL, with Mucor subtilissimus UCP 1262 being the most active. The protease was biochemically and biophysically characterized, showing that the enzyme had a high affinity for SAApNA substrate and was significantly inhibited by fluoride methyl phenyl sulfonyl-C7H7FO2S, suggesting that it is a chymotrypsin-like serine protease. The highest enzyme activity was detected at pH 5.0 and 28 °C. This fibrinolytic protease's far-UV circular dichroism (CD) showed that its secondary structure was primarily α-helical. The purified fibrinolytic enzyme may represent a novel therapeutic agent for treating thrombosis. At temperatures above 65 °C, the enzyme lost all its secondary structure. Its melting temperature was 58.1 °C, the denaturation enthalpy 85.1 kcal/mol, and the denaturation entropy 0.26 kcal/K∙mol.

Anti-hemostatic, antithrombotic, and chemical profiles of a curly-leaf variety of Petroselinum crispum (Apiaceae), a food and medicinal aromatic herb.

Thrombosis is currently among the major causes of morbidity and mortality in the World. New prevention and therapy alternatives have been increasingly sought in medicinal plants. In this context, we have been investigating parsley, Petroselinum crispum (Mill.) Nym, an aromatic herb with two leaf varieties. We report here the in vitro, in vivo, and ex vivo anti-hemostatic and antithrombotic activities of a parsley curly-leaf variety. Aqueous extracts of aerial parts (PCC-AP), stems (PCC-S), and leaves (PCC-L) showed significant in vitro antiplatelet activity. PCC-AP extract exhibited the highest activity (IC50 2.92 mg/mL) when using ADP and collagen as agonists. All extracts also presented in vitro anticoagulant activity (APTT and PT) and anti-thrombogenic activity. PCC-S was the most active, with more significant interference in the factors of the intrinsic coagulation pathway. The oral administration of PCC-AP extract in rats caused a greater inhibitory activity in the deep vein thrombi (50%; 65 mg/kg) than in arterial thrombi formation (50%; 200 mg/kg), without cumulative effect after consecutive five-day administration. PCC-AP extract was safe in the induced bleeding time test. Its anti-aggregating profile was similar in ex vivo and in vitro conditions but was more effective in the extrinsic pathway when compared to in vitro results. Apiin and coumaric acid derivatives are the main compounds in PCC-AP according to the HPLC-DAD-ESI-MS/MS profile. We demonstrated for the first time that extracts from different parts of curly parsley have significant antiplatelet, anticoagulant, and antithrombotic activity without inducing hemorrhage, proving its potential as a source of antithrombotic compounds.

Natural Phenolic Compounds with Antithrombotic and Antiplatelet Effects: A Drug-likeness Approach.

BACKGROUND: Thrombosis is one of the major causes of morbidity and mortality in a wide range of vessel diseases. Several studies have been conducted to identify antithrombotic agents from medicinal plants, and phenolic compounds (PCs) have been shown to effectively inhibit plasma coagulation and platelet aggregation. OBJECTIVES: This study aimed to conduct a survey of the natural PCs with proven antithrombotic and antiplatelet activities, as well as to evaluate by computational modeling the physicochemical and toxicological properties of these compounds using drug-likeness approaches. METHODS: The data were collected from the scientific database: 'Web of Science', 'Scifinder', 'Pubmed', 'ScienceDirect' and 'Google Scholar', the different classes of PCs with antithrombotic or antiplatelet effects were used as keywords. These molecules were also evaluated for their Drug-Likeness properties and toxicity to verify their profile for being candidates for new antithrombotic drugs. RESULTS: In this review, it was possible to register 85 lignans, 73 flavonoids, 28 coumarins, 21 quinones, 23 phenolic acids, 8 xanthones and 8 simple phenols. Activity records for tannins were not found in the researched databases. Of these 246 compounds, 213 did not violate any of Lipinski's rules of five, of which 125 (59%) showed non-toxicity, being promising candidates for new potential antithrombotic drugs. CONCLUSION: This review arouses interest in the isolation of phenolic compounds that may allow a new approach for the prevention of both arterial and venous thrombosis, with the potential to become alternatives in the prevention and treatment of cardiovascular diseases.

Purification, biochemical characterization and fibrinolytic potential of proteases produced by bacteria of the genus Bacillus: a systematic literature review.

Thrombosis is a hematological disorder characterized by the formation of intravascular thrombi, which contributes to the development of cardiovascular diseases. Fibrinolytic enzymes are proteases that promote the hydrolysis of fibrin, promoting the dissolution of thrombi, contributing to the maintenance of adequate blood flow. The characterization of new effective, safe and low-cost fibrinolytic agents is an important strategy for the prevention and treatment of thrombosis. However, the development of new fibrinolytics requires the use of complex methodologies for purification, physicochemical characterization and evaluation of the action potential and toxicity of these enzymes. In this context, microbial enzymes produced by bacteria of the Bacillus genus are promising and widely researched sources to produce new fibrinolytics, with high thrombolytic potential and reduced toxicity. Thus, this review aims to provide a current and comprehensive understanding of the different Bacillus species used for the production of fibrinolytic proteases, highlighting the purification techniques, biochemical characteristics, enzymatic activity and toxicological evaluations used.

Immobilization of fibrinolytic protease from Mucor subtilissimus UCP 1262 in magnetic nanoparticles.

This work reports the immobilization of a fibrinolytic protease (FP) from Mucor subtilissimus UCP 1262 on Fe3O4 magnetic nanoparticles (MNPs) produced by precipitation of FeCl3·6H2O and FeCl2·4H2O, coated with polyaniline and activated with glutaraldehyde. The FP was obtained by solid state fermentation, precipitated with 40-60% ammonium sulfate, and purified by DEAE-Sephadex A50 ion exchange chromatography. The FP immobilization procedure allowed for an enzyme retention of 52.13%. The fibrinolytic protease immobilized on magnetic nanoparticles (MNPs/FP) maintained more than 60% of activity at a temperature of 40 to 60 °C and at pH 7 to 10, when compared to the non-immobilized enzyme. MNPs and MNPs/FP did not show any cytotoxicity against HEK-293 and J774A.1 cells. MNPs/FP was not hemolytic and reduced the hemolysis induced by MNPs from 2.07% to 1.37%. Thrombus degradation by MNPs/FP demonstrated that the immobilization process guaranteed the thrombolytic activity of the enzyme. MNPs/FP showed a total degradation of the γ chain of human fibrinogen within 90 min. These results suggest that MNPs/FP may be used as an alternative strategy to treat cardiovascular diseases with a targeted release through an external magnetic field.

Structural characterization of anticoagulant and antithrombotic polysaccharides isolated from Caesalpinia ferrea stem barks.

This study aimed to isolate, characterize chemical-structurally and evaluate the effects of polysaccharides from Caesalpinia (Libidibia) ferrea stem barks in the haemostatic system. The deproteinated-polysaccharide extract (PE-Cf) after being fractionated by ion exchange chromatography-DEAE-cellulose resulted in three fractions (FI, FII, FIII) containing total carbohydrates (14.3-38%), including uronic acid (5-16%), and polyphenols (0.94-1.7 mg/g GAE). The polysaccharide fractions presented polydisperse profile in polyacrylamide gel electrophoresis (detected by Stains-All) and molecular masses (9.5 × 104 Da-1.5 × 105 Da) identified by gel permeation chromatography. FT-IR showed absorption bands (1630 cm-1, 1396-1331 cm-1), indicative of uronic acid, and a band at 1071 cm-1, typical of COO- groups of galacturonic acid. The NMR spectra of C. ferrea polysaccharides revealed a central core composed mainly by 5-linked α-Araf and minority components as α-Rhap and α-GalAp. UV spectra of fractions revealed discrete shoulders at 269-275 nm, characteristic of polyphenolic compounds. In vitro, polysaccharides inhibited the intrinsic and/or common coagulation pathway (aPTT test) (2.0-3.7 fold) and the platelet aggregation induced by 3 µM adenosine diphosphate (25-48%) and 5 µg/mL collagen (24%), but not that induced by arachidonic acid. In vivo, the polysaccharides inhibited (36-69%) venous thrombosis induced by hypercoagulability and stasis, showing discrete hemorrhagic effect. In conclusion, the polysaccharides of C. ferrea barks, containing arabinose, galactose, rhamnose and uronic acid, possess anticoagulant, antiplatelet and antithrombotic properties of low hemorrhagic risk, suggesting potential applicability in thromboembolic disorders.

Fibrinolytic enzyme from Arthrospira platensis cultivated in medium culture supplemented with corn steep liquor.

Artrhospira (Spirulina) platensis produced fibrinolytic enzyme under mixotrophic conditions using corn steep liquor (CSL). The enzyme was extracted, purified by combination of two chromatographic techniques and biochemically characterized. Maximum fibrinolytic production (268.14 U mg-1) was obtained using liquid medium culture composed by 0.2% CLS after 10th day of cultivation. Fibrinolytic activity was higher when extracted by homogenization methods and was purified 32.72-fold with specific activity of 7988 U mg-1. Fibrin zymography showed an active band, indicated acts as a plasmin-like protein with molecular weight of 72 kDa. Fibrinolytic enzyme have optimum pH of 6.0, stable in the range of 6.0 to 10.0 during 24 h and optimum temperature at 40 °C with a stability below 50 °C. Fibrinolytic enzyme is a serine metalloprotease by to be enhanced by Fe2+ and inhibited by PMSF. The enzyme has higher enzymatic activity than most other fibrinolytic enzymes and is stable at temperature and pH human physiological. Overall, the fibrinolytic enzyme from A. platensis has attractive biochemical properties to potential applications in the treatment of thrombosis.

Sulfated polysaccharide from the red algae Gelidiella acerosa: Anticoagulant, antiplatelet and antithrombotic effects.

A sulfated polysaccharide from the red algae Gelidiella acerosa (GaSP) was obtained through enzymatic extraction and subjected to chemical characterization by HPSEC, elemental microanalysis, FT-IR and NMR spectroscopies. The GaSP anticoagulant activity was investigated through APTT and PT tests and platelet aggregation assessed by turbidimetry. The antithrombotic and hemorrhagic activities were evaluated by venous thrombosis and hemorrhagic tendency models, respectively. FT-IR and NMR demonstrated that GaSP is a sulfated agaran. HPSEC and elemental microanalysis revealed a peak molar mass of 284.8 kDa and a degree of sulfation of 0.63, respectively. This molecule prolonged the coagulation time in 2.1 times and inhibited the platelet aggregation by 45%. Furthermore, it showed significant dose-dependent antithrombotic effect of 40%, 64% and 80% at 0.1, 0.5 and 1 mg/kg, respectively, without hemorrhage. These results suggest that GaSP has promising antithrombotic.

Anticoagulant and antithrombotic effects of chemically sulfated guar gum.

Heparin is an extremely important and recognized anticoagulant and antithrombotic agent. Obtained from animal sources and being highly potent, risks of contamination by pathogens and bleeding are some concerns related to heparin use. In the search for alternatives to heparin, several researches have been performed with chemically sulfated polysaccharides obtained from non-animal sources. In this work, studies with guar gum led to a partially hydrolyzed and chemically sulfated derivative (hGGSL) with Mw of 15.6 kDa, DS of 1.91 and promising anticoagulant and antithrombotic properties. In vitro, hGGSL was only 4.5× less potent than unfractionated heparin, acting mainly by inhibiting thrombin via antithrombin, and had its anticoagulant activity inhibited by protamine. In vivo, hGGSL showed potential for subcutaneous use and was effective in reducing venous thrombosis. Collectively, the results provide a basis for the development of a new anticoagulant and antithrombotic agent.

Molecular interactions between p-coumaric acid and snake venom toxins.

A large number of natural compounds, such as phenolic compounds, have been scientifically evaluated in the search for enzyme inhibitors. The interactions between the phenolic compound p-coumaric acid and the enzymes present in snake venoms (used as research tools) were evaluated in vitro and in silico. The p-coumaric acid was able to inhibit 31% of the phospholipase activity induced by Bothrops alternatus venom, 27% of the hemolytic activity induced by B. moojeni, 62.5% of the thrombolytic activity induced by B. jararacussu, and approximately 27% of the activity thrombosis induced by Crotalus durissus terrificus. Previous incubation of p-coumaric acid with the venoms of B. atrox and B. jararacussu increased the coagulation time by 2.18 and 2.16-fold, respectively. The activity of serine proteases in B. atrox and B. jararacussu venoms was reduced by 60% and 66.34%, respectively. Computational chemistry analyses suggests the specific binding of p-coumaric acid to the active site of proteases through hydrogen and hydrophobic interactions. The phenolic compound evaluated in this work has great potential in therapeutic use to both prevent and treat hemostatic alterations, because the venom proteins inhibited by the p-coumaric acid have high homology with human proteins that have a fundamental role in several pathologies.

Recovery of fibrinolytic and collagenolytic enzymes from fish and shrimp byproducts: potential source for biomedical applications / Recuperação de enzimas fibrinolíticas e colagenolitícas de resíduos de peixes e camarões: fonte potencial para aplicações biomédicas

Fish and shrimp industries generate a significant amount of by-products. These by-products can be used for the extraction of enzymes of biomedical interest, such as fibrinolytic and collagenolytic. Thus, this work aimed to perform a screening of fish and shrimp byproducts as sources of enzymes with fibrinolytic and collagenolytic activities and to characterize the biochemical properties of crude extracts with collagenolytic activity from Cichla ocellaris residues. Fibrinolytic enzymes were recovered with activities between 5.51 ± 0.02 U.mL-1 (Caranx crysos) and 56.16 ± 0.42 U.mL-1 (Litopenaeus vannamei), while collagenolytic enzymes were detected in a range between 6.79 ± 0.00 U.mg-1 (Trachurus lathami) and 94.35 ± 0.02 U.mg-1 (C. ocellaris). After collagenolytic screening, the selected species was C. ocellaris, being subjected to a preheating, which culminated with an increase of enzymatic activity of 35.07% (up to 127.44 ± 0.09 U.mg-1). The optimal collagenolytic activity recovered from C. ocellaris byproducts was 55 °C (thermostable between 25 and 60 °C) and 7.5 (stable between 6.5 and 11.5) for temperature and pH evaluations, respectively. The kinetic parameters were determined, obtaining Km of 5.92 mM and Vmax of 294.40 U.mg-1. The recovered enzyme was sensitive to the Cu2+, Hg2 and Pb2+ ions, being partially inhibited by phenylmethylsulphonyl fluoride (PMSF), N-p-tosyl-L-lysin chloromethyl ketone (TLCK) and Benzamidine. Furthermore, it was able to cleave native type I collagen, the most important type for industry. Thus, the recovery of biomolecules, besides offering to the industry an alternative source of active molecules, contributes to the reduction of the environmental impact, adding value to the fish product and providing a new source of income.

As indústrias de peixe e camarão geram uma quantidade significativa de subprodutos. Estes subprodutos podem ser utilizados para a extração de enzimas de interesse biomédico, como fibrinolítica e o colagenolítica. Assim, este trabalho teve como objetivo realizar uma triagem de subprodutos de peixes e camarões como fontes de enzimas com atividade fibrinolítica e colagenolítica e caracterizar as propriedades bioquímicas do extrato bruto com atividade colagenolítica a partir de resíduos de Cichla ocellaris. Enzimas fibrinolíticas foram recuperadas com atividades entre 5,51 ± 0,02 U.mL-1 (Caranx crysos) e 56,16 ± 0,42 U.mL-1 (Litopenaeus vannamei), enquanto enzimas colagenolitícas foram detectadas numa variação entre 6,79 ± 0,00 U.mg-1 (Trachurus lathami) e 94,35 ± 0,02 U.mg-1 (C. ocellaris). Após a triagem colagenolítica, a espécie selecionada foi a C. ocellaris, sendo submetida a um pré-aquecimento, o que culminou com um aumento de atividade enzimática de 35.07% (127.44 ± 0.09 U.mg-1). A atividade colagenolítica ótima recuperada de resíduos de C. ocellaris foi a 55°C (termoestável entre 25 a 60°) e 7,5 (estável entre 6,5 a 11,5) para avaliações de temperatura e de pH, respectivamente. Os parâmetros cinéticos foram determinados, obtendo-se Km de 5,92 mM e Vmax de 294,40 U.mg-1. A enzima recuperada foi sensível aos íons de Cu2+, Hg2+ e Pb2+, sendo parcialmente inibida por Fluoreto de Fenilmetilsulfonil (PMSF), N-α-tosil-L-lisina clorometil cetona (TLCK) e Benzamidina. Ainda, foi capaz de clivar o colágeno nativo tipo I, o tipo mais desejável pela indústria. Assim, a recuperação de biomoléculas, além de oferecer à indústria uma fonte alternativa de moléculas ativas, contribui para a redução do impacto ambiental, agregando valor ao produto pesqueiro e proporcionando nova fonte de renda.

Recovery of fibrinolytic and collagenolytic enzymes from fish and shrimp byproducts: potential source for biomedical applications / Recuperação de enzimas fibrinolíticas e colagenolitícas de resíduos de peixes e camarões: fonte potencial para aplicações biomédicas

Fish and shrimp industries generate a significant amount of by-products. These by-products can be used for the extraction of enzymes of biomedical interest, such as fibrinolytic and collagenolytic. Thus, this work aimed to perform a screening of fish and shrimp byproducts as sources of enzymes with fibrinolytic and collagenolytic activities and to characterize the biochemical properties of crude extracts with collagenolytic activity from Cichla ocellaris residues. Fibrinolytic enzymes were recovered with activities between 5.51 ± 0.02 U.mL-1 (Caranx crysos) and 56.16 ± 0.42 U.mL-1 (Litopenaeus vannamei), while collagenolytic enzymes were detected in a range between 6.79 ± 0.00 U.mg-1 (Trachurus lathami) and 94.35 ± 0.02 U.mg-1 (C. ocellaris). After collagenolytic screening, the selected species was C. ocellaris, being subjected to a preheating, which culminated with an increase of enzymatic activity of 35.07% (up to 127.44 ± 0.09 U.mg-1). The optimal collagenolytic activity recovered from C. ocellaris byproducts was 55 °C (thermostable between 25 and 60 °C) and 7.5 (stable between 6.5 and 11.5) for temperature and pH evaluations, respectively. The kinetic parameters were determined, obtaining Km of 5.92 mM and Vmax of 294.40 U.mg-1. The recovered enzyme was sensitive to the Cu2+, Hg2 and Pb2+ ions, being partially inhibited by phenylmethylsulphonyl fluoride (PMSF), N-p-tosyl-L-lysin chloromethyl ketone (TLCK) and Benzamidine. Furthermore, it was able to cleave native type I collagen, the most important type for industry. Thus, the recovery of biomolecules, besides offering to the industry an alternative source of active molecules, contributes to the reduction of the environmental impact, adding value to the fish product and providing a new source of income.(AU)

As indústrias de peixe e camarão geram uma quantidade significativa de subprodutos. Estes subprodutos podem ser utilizados para a extração de enzimas de interesse biomédico, como fibrinolítica e o colagenolítica. Assim, este trabalho teve como objetivo realizar uma triagem de subprodutos de peixes e camarões como fontes de enzimas com atividade fibrinolítica e colagenolítica e caracterizar as propriedades bioquímicas do extrato bruto com atividade colagenolítica a partir de resíduos de Cichla ocellaris. Enzimas fibrinolíticas foram recuperadas com atividades entre 5,51 ± 0,02 U.mL-1 (Caranx crysos) e 56,16 ± 0,42 U.mL-1 (Litopenaeus vannamei), enquanto enzimas colagenolitícas foram detectadas numa variação entre 6,79 ± 0,00 U.mg-1 (Trachurus lathami) e 94,35 ± 0,02 U.mg-1 (C. ocellaris). Após a triagem colagenolítica, a espécie selecionada foi a C. ocellaris, sendo submetida a um pré-aquecimento, o que culminou com um aumento de atividade enzimática de 35.07% (127.44 ± 0.09 U.mg-1). A atividade colagenolítica ótima recuperada de resíduos de C. ocellaris foi a 55°C (termoestável entre 25 a 60°) e 7,5 (estável entre 6,5 a 11,5) para avaliações de temperatura e de pH, respectivamente. Os parâmetros cinéticos foram determinados, obtendo-se Km de 5,92 mM e Vmax de 294,40 U.mg-1. A enzima recuperada foi sensível aos íons de Cu2+, Hg2+ e Pb2+, sendo parcialmente inibida por Fluoreto de Fenilmetilsulfonil (PMSF), N-α-tosil-L-lisina clorometil cetona (TLCK) e Benzamidina. Ainda, foi capaz de clivar o colágeno nativo tipo I, o tipo mais desejável pela indústria. Assim, a recuperação de biomoléculas, além de oferecer à indústria uma fonte alternativa de moléculas ativas, contribui para a redução do impacto ambiental, agregando valor ao produto pesqueiro e proporcionando nova fonte de renda.(AU)

Anticoagulant and Antithrombotic Properties of Three Structurally Correlated Sea Urchin Sulfated Glycans and Their Low-Molecular-Weight Derivatives.

The anticoagulant and antithrombotic properties of three structurally correlated sea urchin-derived 3-linked sulfated α-glycans and their low molecular-weight derivatives were screened comparatively through various in vitro and in vivo methods. These methods include activated partial thromboplastin time, the inhibitory activity of antithrombin over thrombin and factor Xa, venous antithrombosis, the inhibition of platelet aggregation, the activation of factor XII, and bleeding. While the 2-sulfated fucan from Strongylocentrotus franciscanus was observed to be poorly active in most assays, the 4-sulfated fucan from Lytechinus variegatus, the 2-sulfated galactan from Echinometra lucunter and their derivatives showed multiple effects. All marine compounds showed no capacity to activate factor XII and similar low bleeding tendencies regardless of the dose concentrations used to achieve the highest antithrombotic effect observed. The 2-sulfated galactan showed the best combination of results. Our work improves the background about the structure-function relationship of the marine sulfated glycans in anticoagulation and antithrombosis. Besides confirming the negative effect of the 2-sulfated fucose and the positive effect of the 2-sulfated galactose on anticoagulation in vitro, our results also demonstrate the importance of this set of structural requirements on antithrombosis in vivo, and further support the involvement of high-molecular weight and 4-sulfated fucose in both activities.

In vitro thrombolytic activity of a purified fibrinolytic enzyme from Chlorella vulgaris.

A fibrinolytic enzyme was produced by microalga Chlorella vulgaris cultivated in autotrophic and mixotrophic conditions added corn steep liquor, purified by a single chromatographic step, then biochemical characterization and in vitro thrombolytic activity was performed. Maximum cell concentration (1637.45 ±â€¯15 mg L-1) and productivity (181.93 mg L-1 day-1) was obtained in mixotrophic culture using 1% corn steep liquor. Enzyme-extracted microalgal biomass was purified by acetone precipitation and DEAE Sephadex anion exchange chromatography up to 2 fold with recovery of 4.0%. After purification, fibrinolytic activity was 1834.6 U mg-1 and 226.86 mm2 by spectrophotometry and fibrin plate assays, respectively. SDS-PAGE results exhibited a protein band of about 45 kDa and fibrinolytic band was detected by fibrin zymography. Enzyme activity was enhanced in the presence of Fe2+ and inhibited by phenylmethane sulfonyl fluoride (PMSF) and ethylenediamine tetracetic acid (EDTA), which suggest it to be a metal-dependent serine protease. The extract also showed a red blood cell lysis <4% and in vitro thrombolytic activity of 25.6% in 90 min of reaction. These results indicate that the fibrinolytic enzyme from C. vulgaris may have potential applications in the prevention and treatment of thrombosis.

Antithrombin conformational modulation by D-myo-inositol 3,4,5,6-tetrakisphosphate (TMI), a novel scaffold for the development of antithrombotic agents.

Antithrombin (AT) is a serpin that inhibits mainly thrombin and fXa after being activated by binding to glycosaminoglycans as heparin and heparan sulfate. Upon binding, the native AT conformation, relatively inactive as a protease inhibitor, is converted to an activated form. Recently, a new compound, named TMI, was discovered in our group with nanomolar affinity to antithrombin, and shown to be able to induce a partial activation of antithrombin. As TMI represents an original scaffold for structural optimizations aiming the development of new antithrombotic drugs, the present work demonstrated, through a series of molecular dynamics simulations, that TMI is able to modulate AT reactive center loop flexibility similarly to what is observed to heparin, as well as exposing AT P1 residue, Arg393. These results represent the first atomic level indication of AT conformational activation by TMI, and may offer a predictive basis for future studies aiming TMI structural optimization.

Direct Fibrinolytic Snake Venom Metalloproteinases Affecting Hemostasis: Structural, Biochemical Features and Therapeutic Potential.

Snake venom metalloproteinases (SVMPs) are predominant in viperid venoms, which provoke hemorrhage and affect hemostasis and thrombosis. P-I class enzymes consist only of a single metalloproteinase domain. Despite sharing high sequence homology, only some of them induce hemorrhage. They have direct fibrin(ogen)olytic activity. Their main biological substrate is fibrin(ogen), whose Aα-chain is degraded rapidly and independently of activation of plasminogen. It is important to understand their biochemical and physiological mechanisms, as well as their applications, to study the etiology of some human diseases and to identify sites of potential intervention. As compared to all current antiplatelet therapies to treat cardiovascular events, the SVMPs have outstanding biochemical attributes: (a) they are insensitive to plasma serine proteinase inhibitors; (b) they have the potential to avoid bleeding risk; (c) mechanistically, they are inactivated/cleared by α2-macroglobulin that limits their range of action in circulation; and (d) few of them also impair platelet aggregation that represent an important target for therapeutic intervention. This review will briefly highlight the structure-function relationships of these few direct-acting fibrinolytic agents, including, barnettlysin-I, isolated from Bothrops barnetti venom, that could be considered as potential agent to treat major thrombotic disorders. Some of their pharmacological advantages are compared with plasmin.

Revisiting antithrombotic therapeutics; sculptin, a novel specific, competitive, reversible, scissile and tight binding inhibitor of thrombin.

Thrombin is a multifunctional enzyme with a key role in the coagulation cascade. Its functional modulation can culminate into normal blood coagulation or thrombosis. Thus, the identification of novel potent inhibitors of thrombin are of immense importance. Sculptin is the first specific thrombin inhibitor identified in the transcriptomics analysis of tick's salivary glands. It consists of 168 residues having four similar repeats and evolutionary diverged from hirudin. Sculptin is a competitive, specific and reversible inhibitor of thrombin with a Ki of 18.3 ± 1.9 pM (k on 4.04 ± 0.03 × 107 M-1 s-1 and k off 0.65 ± 0.04 × 10-3 s-1). It is slowly consumed by thrombin eventually losing its activity. Contrary, sculptin is hydrolyzed by factor Xa and each polypeptide fragment is able to inhibit thrombin independently. A single domain of sculptin alone retains ~45% of inhibitory activity, which could bind thrombin in a bivalent fashion. The formation of a small turn/helical-like structure by active site binding residues of sculptin might have made it a more potent thrombin inhibitor. In addition, sculptin prolongs global coagulation parameters. In conclusion, sculptin and its independent domain(s) have strong potential to become novel antithrombotic therapeutics.

Marine Diterpenes: Molecular Modeling of Thrombin Inhibitors with Potential Biotechnological Application as an Antithrombotic.

Thrombosis related diseases are among the main causes of death and incapacity in the world. Despite the existence of antithrombotic agents available for therapy, they still present adverse effects like hemorrhagic risks which justify the search for new options. Recently, pachydictyol A, isopachydictyol A, and dichotomanol, three diterpenes isolated from Brazilian marine brown alga Dictyota menstrualis were identified as potent antithrombotic molecules through inhibition of thrombin, a key enzyme of coagulation cascade and a platelet agonist. Due to the biotechnological potential of these marine metabolites, in this work we evaluated their binding mode to thrombin in silico and identified structural features related to the activity in order to characterize their molecular mechanism. According to our theoretical studies including structure-activity relationship and molecular docking analysis, the highest dipole moment, polar surface area, and lowest electronic density of dichotomanol are probably involved in its higher inhibition percentage towards thrombin catalytic activity compared to pachydictyol A and isopachydictyol A. Interestingly, the molecular docking studies also revealed a good shape complementarity of pachydictyol A and isopachydictyol A and interactions with important residues and regions (e.g., H57, S195, W215, G216, and loop-60), which probably justify their thrombin inhibitor effects demonstrated in vitro. Finally, this study explored the structural features and binding mode of these three diterpenes in thrombin which reinforced their potential to be further explored and may help in the design of new antithrombotic agents.

Proportion of single-chain recombinant tissue plasminogen activator and outcome after stroke.

OBJECTIVE: To determine whether the ratio single chain (sc)/(sc + 2 chain [tc]) recombinant tissue plasminogen activator (rtPA) influences outcomes in patients with cerebral ischemia. METHODS: We prospectively included consecutive patients treated with IV rtPA for cerebral ischemia in 13 stroke centers and determined the sc/(sc + tc) ratio in the treatment administered to each patient. We evaluated the outcome with the modified Rankin Scale (mRS) at 3 months (prespecified analysis) and occurrence of epileptic seizures (post hoc analysis). We registered Outcome of Patients Treated by IV Rt-PA for Cerebral Ischaemia According to the Ratio Sc-tPA/Tc-tPA (OPHELIE) under ClinicalTrials.gov identifier no. NCT01614080. RESULTS: We recruited 1,004 patients (515 men, median age 75 years, median onset-to-needle time 170 minutes, median NIH Stroke Scale score 10). We found no statistical association between sc/(sc + tc) ratios and handicap (mRS > 1), dependency (mRS > 2), or death at 3 months. Patients with symptomatic intracerebral hemorrhages had lower ratios (median 69% vs 72%, adjusted p = 0.003). The sc/(sc + tc) rtPA ratio did not differ between patients with and without seizures, but patients with early seizures were more likely to have received a sc/(sc + tc) rtPA ratio >80.5% (odds ratio 3.61; 95% confidence interval 1.26-10.34). CONCLUSIONS: The sc/(sc + tc) rtPA ratio does not influence outcomes in patients with cerebral ischemia. The capacity of rtPA to modulate NMDA receptor signaling might be associated with early seizures, but we observed this effect only in patients with a ratio of sc/(sc + tc) rtPA >80.5% in a post hoc analysis.

Fibrin(ogen)olytic and antiplatelet activities of a subtilisin-like protease from Solanum tuberosum (StSBTc-3).

Plant serine proteases have been widely used in food science and technology as well as in medicine. In this sense, several plant serine proteases have been proposed as potential anti-coagulants and anti-platelet agents. Previously, we have reported the purification and identification of a plant serine protease from Solanum tuberosum leaves. This potato enzyme, named as StSBTc-3, has a molecular weight of 72 kDa and it was characterized as a subtilisin like protease. In this work we determine and characterize the biochemical and medicinal properties of StSBTc-3. Results obtained show that, like the reported to other plant serine proteases, StSBTc-3 is able to degrade all chains of human fibrinogen and to produces fibrin clot lysis in a dose dependent manner. The enzyme efficiently hydrolyzes ß subunit followed by partially hydrolyzed α and γ subunits of human fibrinogen. Assays performed to determine StSBTc-3 substrate specificity using oxidized insulin ß-chain as substrate, show seven cleavage sites: Asn3-Gln4; Cys7-Gly8; Glu13-Ala14; Leu15-Tyr16; Tyr16-Leu17; Arg22-Gly23 and Phe25-Tyr26, all of them were previously reported for other serine proteases with fibrinogenolytic activity. The maximum StSBTc-3 fibrinogenolytic activity was determined at pH 8.0 and at 37 C. Additionally, we demonstrate that StSBTc-3 is able to inhibit platelet aggregation and is unable to exert cytotoxic activity on human erythrocytes in vitro at all concentrations assayed. These results suggest that StSBTc-3 could be evaluated as a new agent to be used in the treatment of thromboembolic disorders such as strokes, pulmonary embolism and deep vein thrombosis.