Fibrin and Fibrinolytic Enzyme Cascade in Thrombosis: Unravelling the Role.

Blood clot formation in blood vessels (thrombosis) is a major cause of life-threatening cardiovascular diseases. These clots are formed by αA-, ßB-, and ϒ-peptide chains of fibrinogen joined together by isopeptide bonds with the help of blood coagulation factor XIIIa. These clot structures are altered by various factors such as thrombin, platelets, transglutaminase, DNA, histones, and red blood cells. Various factors are used to dissolve the blood clot, such as anticoagulant agents, antiplatelets drugs, fibrinolytic enzymes, and surgical operations. Fibrinolytic enzymes are produced by microorganisms (bacteria, fungi, etc.): streptokinase of Streptococcus hemolyticus, nattokinase of Bacillus subtilis YF 38, bafibrinase of Bacillus sp. AS-S20-I, longolytin of Arthrobotrys longa, versiase of Aspergillus versicolor ZLH-1, etc. They act as a thrombolytic agent by either enhancing the production of plasminogen activators (tissue or urokinase types), which convert inactive plasminogen to active plasmin, or acting as plasmin-like proteins themselves, forming fibrin degradation products which cause normal blood flow again in blood vessels. Fibrinolytic enzymes may be classified in two groups, as serine proteases and metalloproteases, based on their catalytic properties, consisting of a catalytic triad responsible for their fibrinolytic activity having different physiochemical properties (such as molecular weight, pH, and temperature). The analysis of fibrinolysis helps to detect hyperfibrinolysis (menorrhagia, renal failure, etc.) and hypofibrinolysis (diabetes, obesity, etc.) with the help of various fibrinolytic assays such as a fibrin plate assay, fibrin microplate assay, the viscoelastic method, etc. These fibrinolytic activities serve as a key aspect in the recognition of numerous cardiovascular diseases and can be easily produced on a large scale with a short generation time by microbes and are less expensive.

Hemostatically Active Proteinase Produced by Aspergillus ochraceus: Key Specific Properties and Effect on Target Proteins.

The effect of A. ochraceus proteinase on the proteins of the human hemostasis system, fibrin, fibrinogen, plasminogen, protein C, and factor X, was studied. These proteins are key targets for proteolytic enzymes in therapy and diagnosis of thromboembolic complications. It was shown that A. ochraceus proteinase efficiently cleaves fibrin and fibrinogen, but does not act precisely, since it cuts all three subunits of these proteins. The proteinase did not have an activating effect on the plasminogen, a precursor of plasminogen and plasmin. The proteinase of A. ochraceus was shown to be the first fungal proteinase with proven activating activity towards the human hemostasis system factors protein C and factor X. For protein C activation, A. ochraceus proteinase requires Ca2+ ions. The enzyme was found to be sensitive to thrombin inhibitors, but not to plasmin inhibitors. A proteolytic action profile of the scope of this proteinase as a proteinase with activating protein C, factor X, and plasmin-like activity was proposed.

Keratinolytic Properties of Aspergillus clavatus Promising for Biodegradation.

The high demand for keratinolytic enzymes and the modest presentation of fungal keratinase diversity studies in scientific sources cause a significant interest in identifying new fungal strains of keratinase producers, isolating new enzymes and studying their properties. Four out of the 32 cultures showed a promising target activity on protein-containing agar plates-Aspergillus amstelodami A6, A. clavatus VKPM F-1593, A. ochraceus 247, and Cladosporium sphaerospermum 1779. The highest values of keratinolytic activity were demonstrated by extracellular proteins synthesized by Aspergillus clavatus VKPM F-1593 cultivated under submerged conditions on a medium containing milled chicken feathers. The enzyme complex preparation was obtained by protein precipitation from the culture liquid with ammonium sulfate, subsequent dialysis, and lyophilization. The fraction of a pure enzyme with keratinolytic activity (pI 9.3) was isolated by separating the extracellular proteins of A. clavatus VKPM F-1593 via isoelectric focusing. The studied keratinase was an alkaline subtilisin-like non-glycosylated protease active over a wide pH range with optimum keratinolysis at pH 8 and 50 °C.

Chicken Feather Waste Valorization Into Nutritive Protein Hydrolysate: Role of Novel Thermostable Keratinase From Bacillus pacificus RSA27.

Microbial keratinases exhibit a momentous role in converting keratin biowastes into exceedingly valuable protein supplements. This study reports a novel, highly stable keratinase from Bacillus pacificus RSA27 for the production of pure peptides rich in essential amino acids from chicken feathers. Purified keratinase showed a specific activity of 38.73 U/mg, 2.58-fold purification, and molecular weight of 36 kDa. Kinetic studies using a chicken feather as substrate report K m and V max values of 5.69 mg/ml and 142.40 µg/ml/min, respectively, suggesting significant enzyme-substrate affinity/biocatalysis. Identification and in silico structural-functional analysis of keratinase discovered the presence of distinct amino acid residues and their positions. Besides, keratinase possesses a high-affinity calcium-binding site (Asp128, Leu162, Asn164, Ile166, and Val168) and a catalytic triad of Asp119, His151, and Ser308, known attributes of serine protease (subtilisin family). Furthermore, a scale-up to 5 L fermenter revealed complete feather hydrolysis (94.5%) within 24 h with high activity (789 U/ml) and total amino acid of 153.97 µmol/ml. Finally, cytotoxicity evaluation of protein hydrolysate resulted in negligible cytotoxic effects (1.02%) on the mammalian hepatoblastoma cell line, signifying its potential biotechnological applications.

Sustainable Applications of Animal Waste Proteins.

Currently, the growth of the global population leads to an increase in demand for agricultural products. Expanding the obtaining and consumption of food products results in a scale up in the amount of by-products formed, the development of processing methods for which is becoming an urgent task of modern science. Collagen and keratin make up a significant part of the animal origin protein waste, and the potential for their biotechnological application is almost inexhaustible. The specific fibrillar structure allows collagen and keratin to be in demand in bioengineering in various forms and formats, as a basis for obtaining hydrogels, nanoparticles and scaffolds for regenerative medicine and targeted drug delivery, films for the development of biodegradable packaging materials, etc. This review describes the variety of sustainable sources of collagen and keratin and the beneficial application multiformity of these proteins.

Microbial Fibrinolytic Enzymes as Anti-Thrombotics: Production, Characterisation and Prodigious Biopharmaceutical Applications.

Cardiac disorders such as acute myocardial infarction, embolism and stroke are primarily attributed to excessive fibrin accumulation in the blood vessels, usually consequential in thrombosis. Numerous methodologies including the use of anti-coagulants, anti-platelet drugs, surgical operations and fibrinolytic enzymes are employed for the dissolution of fibrin clots and hence ameliorate thrombosis. Microbial fibrinolytic enzymes have attracted much more attention in the management of cardiovascular disorders than typical anti-thrombotic strategies because of the undesirable after-effects and high expense of the latter. Fibrinolytic enzymes such as plasminogen activators and plasmin-like proteins hydrolyse thrombi with high efficacy with no significant after-effects and can be cost effectively produced on a large scale with a short generation time. However, the hunt for novel fibrinolytic enzymes necessitates complex purification stages, physiochemical and structural-functional attributes, which provide an insight into their mechanism of action. Besides, strain improvement and molecular technologies such as cloning, overexpression and the construction of genetically modified strains for the enhanced production of fibrinolytic enzymes significantly improve their thrombolytic potential. In addition, the unconventional applicability of some fibrinolytic enzymes paves their way for protein hydrolysis in addition to fibrin/thrombi, blood pressure regulation, anti-microbials, detergent additives for blood stain removal, preventing dental caries, anti-inflammatory and mucolytic expectorant agents. Therefore, this review article encompasses the production, biochemical/structure-function properties, thrombolytic potential and other surplus applications of microbial fibrinolytic enzymes.

Acute Toxicity, Immunotoxicity and Allergenicity of Protease Complex Obtained from Micromycete Sarocladium strictum.

The different effects on animals of the thrombolytic protease complex of the new producer S. strictum 203 were studied. The tests of acute toxicity, immunotoxicity and allergenicity should conclude that the studied proteolytic complex is safe for medical usage. For the intravenous and the intraperitoneal routes of administration, the maximum tolerated dose and the median lethal dose were not determined.

Gene Analysis, Cloning, and Heterologous Expression of Protease from a Micromycete Aspergillus ochraceus Capable of Activating Protein C of Blood Plasma.

Micromycetes are known to secrete numerous enzymes of biotechnological and medical potential. Fibrinolytic protease-activator of protein C (PAPC) of blood plasma from micromycete Aspergillus ochraceus VKM-F4104D was obtained in recombinant form utilising the bacterial expression system. This enzyme, which belongs to the proteinase-K-like proteases, is similar to the proteases encoded in the genomes of Aspergillus fumigatus ATCC MYA-4609, A. oryzae ATCC 42149 and A. flavus 28. Mature PAPC-4104 is 282 amino acids long, preceded by the 101-amino acid propeptide necessary for proper folding and maturation. The recombinant protease was identical to the native enzyme from micromycete in terms of its biological properties, including an ability to hydrolyse substrates of activated protein C (pGlu-Pro-Arg-pNA) and factor Xa (Z-D-Arg-Gly-Arg-pNA) in conjugant reactions with human blood plasma. Therefore, recombinant PAPC-4104 can potentially be used in medicine, veterinary science, diagnostics, and other applications.

Action of Extracellular Proteases of Aspergillus flavus and Aspergillus ochraceus Micromycetes on Plasma Hemostasis Proteins.

In this study, we investigated the properties of proteolytic enzymes of two species of Aspergillus, Aspergillus flavus 1 (with a high degree of pathogenicity) and Aspergillus ochraceus L-1 (a conditional pathogen), and their effects on various components of the hemostasis system (in vitro) in the case of their penetration into the bloodstream. We showed that micromycete proteases were highly active in cleaving both globular (albuminolysis) and fibrillar (fibrin) proteins, and, to varying degrees, they could coagulate the plasma of humans and animals (due to proteolysis of factors of the blood coagulation cascade) but were not able to coagulate fibrinogen. The proteases of both Aspergillus fully hydrolyzed thrombi in 120-180 min. Micromycetes did not show hemolytic activity but were able to break down hemoglobin.

Vermiculite as a new carrier for extracellular protease production by Aspergillus spp. under solid-state fermentation.

A new method has been developed to increase the productivity of aspergilli - producers of extracellular proteinases based on their cultivation on vermiculite under solid-state fermentation conditions. The productivity of the mycelium Aspergillus ochraceus L-1 and Aspergillus ustus 1 was 3-18 times higher not only in comparison with submerged cultivation, but also in comparison with growth on other carriers studied under solid-state fermentation conditions. Vermiculite can be considered as a new promising carrier for solid-state fermentation of micromycetes.

Combined microbiological approach to screening of producers of proteases with hemostasis system proteins activity among micromycetes.

A scheme for screening of micromycetes - producers of proteases with the activity of hemostasis system proteins, based on their enzymatic indices determination and the activity towards chromogenic peptide substrates for proteins of the hemostasis system was developed. Depending on the ability of proteases producers to cleave such substrates, an enzymatic reaction in conditions containing human plasma is suggested, which makes it possible to identify the potentiality of the target plasma hemostasis proenzymes activation.