Purification and characterization of a novel fibrinolytic enzyme from Bacillus sp. nov. SK006 isolated from an Asian traditional fermented shrimp paste

Partial purification and characterization of protease extracted from kinema

Proteases are large group of highly demanded enzymes having huge application in food and pharmaceutical industries. Numerous sources, including plants, microorganisms, and animals, can be used to obtain protease. Due to its affordability and safety consideration, fermented foods have recently attracted more attention as a source of microbial protease. The present study aimed to extract protease from kinema, partially purify the extracted protease following dialysis after precipitation with ammonium sulfate, and determine general characteristics of protease. The kinema having highest proteolysis activity after three days of control fermentation (Temperature 30±2 °C, RH 66 ± 2%) was taken for the study. About 2.45 fold of purification with overall recovery of 63.21% was achieved after precipitation with ammonium sulfate at 30-70% saturation level followed by dialysis of crude extracted protease. The dialysed kinema protease had specific activity of 7.90 U/mg. The enzyme remained actively functional across a wider pH (5-9) and temperature (40-60 °C) range. SDS-PAGE and Zymogram confirmed the presence of three major active bands respectively of 29.04 kDa, 36.09 kDa and 46.35 kDa in the kinema protease extract. The enzyme kinetics data on casein, fitted to Mechaelis Mentens' plots showed the protease had Vmax of 1.001 U/ml with corresponding Km value of 0.825 mg/ml. Metal ions such as iron, mercury and aluminium showed the inhibition effect whereas presence of sodium, zinc, and calcium shows the activation effect on protease performance. The enzyme was active over various natural substrates; showing maximal activity on casein, and subsequent to bovine serum albumin, gelatin, hemoglobin and whey protein respectively. Furthermore, molecular weight distribution of the protease extract and activity inhibition with ethylenediaminetetraacetic acid and phenylmethylsulfonyl fluoride, suggesting the protease from kinema could be a metal dependent serine protease or mixture of them.

Diverse origins of fibrinolytic enzymes: A comprehensive review

Fibrinolytic enzymes cleave fibrin which plays a crucial role in thrombus formation which otherwise leads to cardiovascular diseases. While different fibrinolytic enzymes have been purified, only a few have been utilized as clinical and therapeutic agents; hence, the search continues for a fibrinolytic enzyme with high specificity, fewer side effects, and one that can be mass-produced at a lower cost with a higher yield. In this context, this review discusses the physiological mechanism of thrombus formation and fibrinolysis, and current thrombolytic drugs in use. Additionally, an overview of the optimization, production, and purification of fibrinolytic enzymes and the role of Artificial Intelligence (AI) in optimization and the patents granted is provided. This review classifies microbial as well as non-microbial fibrinolytic enzymes isolated from food sources, including fermented foods and non-food sources, highlighting their advantages and disadvantages. Despite holding immense potential for the discovery of novel fibrinolytic enzymes, only a few fermented food sources limited to Asian countries have been studied, necessitating the research on fibrinolytic enzymes from fermented foods of other regions. This review will aid researchers in selecting optimal sources for screening fibrinolytic enzymes and is the first one to provide insights and draw a link between the implication of source selection and in vivo application.

Thrombolytic and anticoagulant efficiencies of purified fibrinolytic enzyme produced from Cochliobolus hawaiiensis under solid-state fermentation

Cochliobolus hawaiiensis Alcorn Assiut University Mycological Centre 8606 was chosen from the screened 20 fungal species as the potent producer of fibrinolytic enzyme on skimmed-milk agar plates. The greatest enzyme yield was attained when the submerged fermentation (SmF) conditions were optimized, and it was around (39.7 U/mg protein). Moreover, upon optimization of fibrinolytic enzyme production under solid-state fermentation (SSF), the maximum productivity of fibrinolytic enzyme was greatly increased recorded a bout (405 U/mg protein) on sugarcane bagasse, incubation period of 5 days, moisture level of 100%, initial pH of salt basal medium 7.8, incubation temperature at 35°C, and supplementation of the salt basal medium with corn steep liquor (80％, v/v). The yield of fibrinolytic enzyme by C. hawaiiensis under SSF was higher than that of SmF with about 10.20-fold. The purification procedures of fibrinolytic enzyme by ammonium sulfate (70%), gel filtration, and ion-exchange columns chromatography caused a great increase in its specific activity to 2581.6 U/mg protein with an overall yield of 55.89%, 6.37 purification fold and molecular weight of 35 kDa. Maximal activity was recorded at pH 7 and 37°C. Significant pH stability was recorded at pH 6.6-7.2, and thermal stability was recorded at 33-41°C. The enzyme showed the highest affinity toward fibrin, with Vmax of 240 U/mL and an apparent Km value of 47.61 mmol. Mg2+ and Ca2+ moderately induced fibrinolytic activity, whereas Cu2+ and Zn2+ greatly suppressed the enzyme activity. The produced enzyme is categorized as serine protease and non-metalloprotease. The purified fibrinolytic enzyme showed efficient thrombolytic and antiplatelet aggregation activities by completely prevention and dissolution of the blood clot which confirmed by microscopic examination and amelioration of blood coagulation assays. These findings suggested that the produced fibrinolytic enzyme is a promising agent in management of blood coagulation disorders.

Research progress on the fibrinolytic enzymes produced from traditional fermented foods

Cardiovascular diseases (CVDs) are a global health problem and leading cause of death worldwide. Thrombus formation, one of the CVDs, is essentially the formation of fibrin clots. The existing thrombolytic agents have the disadvantages of high price, short half-life, and high bleeding risk; hence, there is an urgent need to find the alternative thrombolytic agents. In recent years, traditional fermented foods have been widely investigated for their outstanding effects in the prevention and treatment of thrombus formation. In this review, we have focused on fibrinolytic enzymes produced by microorganisms during the fermentation of traditional fermented foods and their potential use for treating CVDs. First, we discussed about the sources of fibrinolytic enzymes and microbial strains that produce those enzymes followed by the optimization of fermentation process, purification, and physicochemical properties of fibrinolytic enzymes. Finally, we have summarized the thrombolytic effects of fibrinolytic enzymes in humans and mice. Fibrinolytic enzymes produced by microorganisms during the fermentation of traditional fermented foods not only lyse thrombi but also acts as anti-atherosclerotic, anti-hyperlipidemia, and neuroprotection agents. Therefore, fibrinolytic enzymes from traditional fermented foods have great potential for the prevention and treatment of CVDs.

A Novel Fibrinolytic Protein From Pheretima vulgaris: Purification, Identification, Antithrombotic Evaluation, and Mechanisms Investigation

Thrombotic diseases have been considered major causes of death around the world. Treatments with thrombolytic drugs, such as recombinant tissue-plasminogen activator, urokinase, and streptokinase, are reported to have a life-threatening bleeding tendency. On the contrary, lumbrokinase, identified from Lumbricus rubellus, is specific to fibrin and does not cause excessive bleeding. It possesses fibrinolytic activity and activation of plasminogen to dissolve fibrin. Hence, the purification of fibrinolytic protein monomer from earthworm and antithrombotic evaluation and investigation of mechanisms are needed. In this study, a novel fibrinolytic protein EPF3, with strong fibrinolytic activity, was purified from Pheretima vulgaris by ion exchange and size exclusion chromatography. SDS PAGE, bottom-up proteomics analysis, de novo sequencing, and circular dichroism (CD) analysis were carried out for identification and characterization of it. EPF3, with a molecular weight of 25136.24 Da, consisted of 241 amino acids and contained various forms of secondary structures, including α-helix (3.9%), β-sheet (42.8%), β-turn (21.2%), and random coil (32.1%). It was a trypsin-like serine protease and stable at pH 7.0 to 11.0 and below 40°C. EPF3 was confirmed to possess an antithrombotic effect by ex vivo clot lysis test and fibrinogen-thrombin time (Fib-TT) assay. The three-dimensional structure of EPF3 was predicted by SWISS-MODEL. Molecular docking analysis predicted that EPF3 could directly interact with antithrombotic target proteins (fibrin, fibrinogen, and plasminogen), which was further confirmed by further studies. The antithrombotic mechanism of EPF3 was clarified to be outstanding direct fibrinolysis, fibrinogenolytic activity, and certain activation of plasminogen. EPF3 possesses the potential to be developed into a promising antithrombotic agent.

Production, purification and characterization of a novel antithrombotic and anticoagulant serine protease from food grade microorganism Neurospora crassa

A novel thrombolytic enzyme was produced by food grade microorganism Neurospora crassa using agro-industrial by-products as substrates. Process parameters were optimized using Plackett-Berman and Box-Benhken design. Under the optimized fermentation conditions, high fibrinolytic activity of 403.59 U/mL was obtained. It was purified with a specific activity of 3572.4 U/mg by ammonium sulfate precipitation and SP Sepharose chromatography. The molecular weight of the enzyme was approximately 32 kDa. It exhibited maximum activity at 40 °C and pH 7.4. Its activity was enhanced by Cu²⁺, Na⁺, Zn²⁺, and completely inhibited by phenylmethanesulfonyl fluoride, soybean trypsin inhibitor, aprotinin, which indicates it could be a serine protease. The enzyme could degrade fibrin clot directly without the need of plasminogen activator, and effectively cleaved Aα, Bβ, γ chains of fibrinogen. It could inhibit the formation of blood clots in vitro and acts as an anticoagulant. Compared to heparin the purified enzyme showed extended anticoagulant activity. Blood clots were dissolved effectively and dissolution rate was increased with time. Based on these results, this novel enzyme has the potential to be developed as a thrombolytic agent.

Characterization of a salt-resistant fibrinolytic protease of Bacillus licheniformis HJ4 isolated from Hwangseokae jeotgal, a traditional Korean fermented seafood

Bacillus licheniformis HJ4 showing strong fibrinolytic activity was isolated from Hwangseokae jeotgal. aprEHJ4, a major fibrinolytic gene, was cloned by PCR, and an ORF consisting of 379 amino acids was located. The mature enzyme was expected to be 27 kDa in size after processing, but a 24-kDa protein was observed by SDS-PAGE and fibrin zymography, indicating additional processing. RT-qPCR showed that expression level of aprEHJ4 in culture with 0% salt (control) was the highest followed by culture with 8% salt (89.7% of control) and 5% salt (74.2%) at 84 h. The expression level in culture with 15% salt was 46.9%. The results matched with the fibrinolytic activity measurements of cultures and indicated that AprEHJ4 maintained significant activity in the presence of salt up to 15% (w/v). AprEHJ4 was overproduced in Escherichia coli, and mature 27 kDa protein was purified after in vitro renaturation. The optimum pH and temperature of AprEHJ4 were pH 8 and 40 ℃, respectively.

In vitro fibrinolytic activity of an enzyme purified from Bacillus amyloliquefaciens strain KJ10 isolated from soybean paste

A fibrinolytic protease secreting producing Bacillus amyloliquefaciens strain KJ10 was initially screened from the fermented soybean. Maximum productivity was obtained in the culture medium after 40 h incubation, 34 °C incubation temperature at pH 8.0. Fibrinolytic protease production was enhanced in the culture medium with 1% sucrose (3712 ± 52 U/mL), 1% (w/v) yeast extract (3940 ± 28 U/mL) and 0.1% MgSO₄ (3687 ± 38 U/mL). Enzyme was purified up to 22.9-fold with 26%recovery after Q-Sepharose HP column chromatography. After three steps purification, enzyme activity was 1606U/mg and SDS-PAGE analysis revealed 29 kDa protein and enzyme band was detected by zymograpy. Enzyme was highly active at pH 8.0, at wide temperature ranges (40 °C − 55 °C) and was activated by Mn²⁺ (102 ± 3.1%) and Mg²⁺ (101.4 ± 2.9%) ions. The purified fibrinolytic enzyme was highly specific against N-Suc-Ala-Ala-Pro-Phe-pNA (189 mmol/min/mL) and clot lytic activity reached 28 ± 1.8% within 60 minin vitro. The purified fibrinolytic enzyme showed least erythrocytic lysis activity confirmed safety to prevent various health risks, including hemolytic anemia. Based on this study, administration of fibrinolytic enzyme from B. amyloliquefaciens strain KJ10 is safe for clinical applications.

Purification, characterization, and chemical modification of Bacillus velezensis SN-14 fibrinolytic enzyme

Fermented bean foods are a crucial source of fibrinolytic enzymes. The presented study aimed to purify, characterize, and chemically modify Bacillus velezensis SN-14 fibrinolytic enzyme. The fibrinolytic enzyme was purified using CTAB/isooctane/hexyl alcohol/n-butyl alcohol reverse micellar system, and the purified enzyme was chemically modified to improve its enzymatic activity and stability. Enzyme activity recovery and the purification fold for this enzyme were 44.5 ± 1.9% and 4.93 ± 0.05 fold, respectively. SDS-PAGE results showed that the molecular weight of the purified fibrinolytic enzyme was around 28 kDa. Besides, the optimum temperature and pH of the purified fibrinolytic enzyme were 37 °C and 8-9, respectively. Fe²⁺, mPEG5000, and pepsin were used for chemical modification and for improving the activity and stability of the purified enzyme. Thermal and acid-base stability of chemically modified enzymes increased significantly, whereas enzymatic activity increased by 7.3 times. After 30 d of frozen storage, the modified enzyme's activity was remarkably lower (33.2%) than the unmodified enzyme (60.6%). The current study on B. velezensis SN-14 fibrinolytic enzyme and chemical modification method using Fe²⁺, mPEG5000, and pepsin provide a reference for developing fibrinolytic drugs and foods.

Cloning of a Novel vpr Gene Encoding a Minor Fibrinolytic Enzyme from Bacillus subtilis SJ4 and the Properties of Vpr

We have previously characterized AprESJ4, the major fibrinolytic enzyme from Bacillus subtilis SJ4 (Yao et al., 2019). During that study, we observed a 68 kDa protein with fibrinolytic activity. In this study, we cloned the gene (vprSJ4) encoding the 68 kDa protein, a mature Vpr and minor protease secreted by Bacillus species. vprSJ4 encodes a preproenzyme consisting of 810 amino acids (aa) including signal sequence (28 aa) and prosequence (132 aa). The mature enzyme (650 aa) has a predicted molecular weight of 68,467.35. Unlike Vprs from other B. subtilis strains, VprSJ4 has 4 additional amino acids (DEFA) at the C-terminus. vprSJ4 was overexpressed in Escherichia coli. PreproVprSJ4 was localized in inclusion bodies, and subjected to in vitro renaturation and purification by an affinity column. SDS-PAGE and western blot showed that autoprocessing of preproVprSJ4 occurred and 68 kDa and smaller proteins were produced. The optimum pH and temperature of the recombinant VprSJ4 were pH 7.0 and 40°C, respectively. Kinetic parameters of recombinant VprSJ4 were measured by using an artificial substrate, N-succinyl-ala-ala-pro-phe-p-nitroanilide. Coexpression of vprSJ4 and aprESJ4 using pHY300PLK increased the fibrinolytic activity a further 117% when compared with aprESJ4 single expression using the same vector in B. subtilis WB600.

Purification, physicochemical properties, and statistical optimization of fibrinolytic enzymes especially from fermented foods: A comprehensive review

Fibrinolytic enzymes are proteases responsible for cleavage of fibrin mesh in thrombus clots, which are the primary causative agents in cardiovascular diseases. Developing safe, effective and cheap thrombolytic agents are important for prevention and cure of thrombosis. Although a wide variety of sources have been discovered for fibrinolytic enzymes, only few of them have been employed in clinical and therapeutic applications due to the drawbacks such as high cost of production, low stability of enzyme or therapeutic side effects. However, the discovery of new fibrinolytic enzymes requires complex purification stages and characterization, which gives an insight into their diverse modes of action. Post-discovery, approaches such as a) statistical optimization for fermentative bioprocessing and b) genetic engineering are advantageous in providing economic viability by finding simple and cost-effective medium, strain development with sufficient nutrient supplements for stable and high-level production of recombinant enzyme. This review provides a comprehensive understanding of different sources, purification techniques, production through genetic engineering approaches and statistical optimization of fermentation parameters as proteases have a wide variety of industrial and biotechnological applications making 60% of total enzyme market worldwide. New strategies targeting increased enzyme yields, non-denaturing environments, improved stability, enzyme activity and strain improvement have been discussed.

Purification and characterization of a novel, highly potent fibrinolytic enzyme from Bacillus subtilis DC27 screened from Douchi, a traditional Chinese fermented soybean food

The highly fibrinolytic enzyme-producing bacterium was identified as Bacillus subtilis DC27 and isolated from Douchi, a traditional fermented soybean food. The DFE27 enzyme was purified from the fermentation broth of B. subtilis DC27 by using UNOsphere Q column chromatography, Sephadex G-75 gel filtration, and high-performance liquid chromatography. It was 29 kDa in molecular mass and showed the optimal reaction temperature and pH value of 45 °C and 7.0, respectively, with a stable fibrinolytic activity below 50 °C and within the pH range of 6.0 to 10.0. DFE27 was identified as a serine protease due to its complete inhibition by phenylmethysulfony fluoride. The first 24 amino acid residues of the N-terminal sequence of the enzyme were AQSVPYGVSQIKAPALHSQGFTGS. The enzyme displayed the highest specificity toward the substrate D-Val-Leu-Lys-pNA for plasmin and it could not only directly degrade but also hydrolyze fibrin by activating plasminogen into plasmin. Overall, the DFE27 enzyme was obviously different from other known fibrinolytic enzymes in the optimum substrate specificity or fibrinolytic action mode, suggesting that it is a novel fibrinolytic enzyme and may have potential applications in the treatment and prevention of thrombosis.

Properties of a fibrinolytic enzyme secreted by Bacillus subtilis JS2 isolated from saeu (small shrimp) jeotgal

Bacillus species were screened to be used as starters for jeotgals, salted and fermented Korean sea foods. A strain, JS2, showing strong fibrinolytic activity was isolated from saeu (small shrimp) jeotgal, and identified as Bacillus subtilis. Bacillus subtilis JS2 grew well at 20% (w/v) NaCl concentration. SDS-PAGE of culture supernatant from JS2 showed 3 major bands of 27, 29, and 60 kDa in size. Fibrin zymography showed that the 27 kDa band was the major fibrinolytic protein. The gene, aprEJS2, was cloned and introduced into B. subtilis WB600 using pHY300PLK. A B. subtilis transformant harboring pHYJS2 showed higher fibrinolytic activity than B. subtilis JS2. aprEJS2 was overexpressed in Escherichia coli BL21 (DE3). The optimum pH and temperature for AprEJS2 were pH 8.0 and 40 °C, respectively. Km and Vmax values were determined. AprEJS2 has strong α-fibrinogenase activity and moderate β-fibrinogenase activity.

Purification and characterization of fibrinolytic enzyme from a bacterium isolated from soil

A novel extracellular enzyme with strong fibrinolytic activity, produced by Bacillus tequilensis, which was isolated from the soil of Zhuhai City (China) was purified and characterized. The enzyme was secreted by cultured B. tequilensis in solid state and purified at a high efficiency using the combination of salting out, ion exchange chromatography, and size exclusion chromatography. The enzyme was estimated to have a molecular weight of approximately 27 kDa, pI of 8.9 ± 0.1, to stable at pH 5.0-12.0 and up to 50 °C; the optimum pH and temperature are 10.5 and 45 °C (2373.59 ± 54.81 U/mg), respectively. The fibrinolytic activity was enhanced by K⁺, Na⁺, Mg²⁺, Mn²⁺, Ca²⁺, and Ba²⁺ and inhibited by Cu²⁺, Zn²⁺, and Fe³⁺. Moreover, the activity was slightly enhanced by PMSF and EDTA at low concentrations and inhibited by β-mercaptoethanol. The N-terminal amino acid sequence is AQSVPYGISQI. The enzyme has a higher enzymatic activity than most other fibrinolytic enzymes. The high thermal stability indicated that it is easy to preserve and could be activated under high-temperature conditions.

Purification, biochemical, and thermal properties of fibrinolytic enzyme secreted by Bacillus cereus SRM-001

The discovery of microbial fibrinolytic enzymes is essential to treat cardiovascular diseases. This study reports the discovery of a fibrinolytic enzyme secreted by Bacillus cereus SRM-001, a microorganism isolated from the soil of a chicken waste-dump yard. The B. cereus SRM-001 was cultured and the secreted fibrinolytic enzyme purified to show that it is a ∼28 kDa protein. The purified enzyme was characterized for its kinetics, biochemical and thermal properties to show that it possesses properties similar to plasmin. A HPLC-MS/MS analysis of trypsin digested protein indicated that the fibrinolytic enzyme shared close sequence homology with serine proteases reported for other Bacillus sp. The results show that the B. cereus SRM-001 secreted enzyme is a ∼28 kDa serine protease that possesses fibrinolytic potential.

Thrombus Degradation by Fibrinolytic Enzyme of Stenotrophomonas sp. Originated from Indonesian Soybean-Based Fermented Food on Wistar Rats

Objective. To evaluate thrombus degrading effect of a fibrinolytic enzyme from food origin Stenotrophomonas sp. of Indonesia. Methods. Prior to animal study, the enzyme safety was tested using cell culture. The effect on expression of tissue plasminogen activator was also analysed in the cell culture. For in vivo studies, 25 Wistar rats were used: normal control, negative control, treatment groups with crude and semipurified enzyme given orally at 25 mg/kg, and positive control group which received Lumbrokinase at 25 mg/kg. Blood clot in the tail was induced by kappa carrageenan injection at 1 mg/kg BW. Results. Experiment with cell culture confirmed the enzyme safety at the concentration used and increased expression of tPA. Decreasing of thrombus was observed in the positive group down to 70.35 ± 23.11% of the negative control animals (100%). The thrombus observed in the crude enzyme treatment was down to 56.99 ± 15.95% and 71.5 ± 15.7% for semipurified enzyme. Scanning electron microscopy showed clearly that bood clots were found in the animals injected with kappa carrageenan; however, in the treatment and positive groups, the clot was much reduced. Conclusions. Oral treatment of enzyme from Stenotrophomonas sp. of Indonesian fermented food was capable of degrading thrombus induced in Wistar rats.

A low cost fermentation medium for potential fibrinolytic enzyme production by a newly isolated marine bacterium, Shewanella sp. IND20

Agro-residues were used as the substrate for the production of fibrinolytic enzyme in solid state fermentation. In this study, two-level full factorial design (2⁵) and response surface methodology were applied to optimize a fermentation medium for the production of fibrinolytic enzyme from the marine isolate Shewanella sp. IND20. The 2⁵ factorial design demonstrated that the physical factors (pH and moisture) and nutrient factors (trehalose, casein, and sodium dihydrogen phosphate) had significant effect on fibrinolytic enzyme production. Central composite design was employed to search for the optimal concentration of the three factors, namely moisture, pH, and trehalose, and the experimental results were fitted with a second-order polynomial model at 99% level (p < 0.0001). The optimized medium showed 2751 U/mL of fibrinolytic activity, which was 2.5-fold higher than unoptimized medium. The molecular weight of fibrinolytic enzyme was found to be 55.5 kDa. The optimum pH and temperature were 8.0 and 50 °C, respectively.

Purification and biochemical characterization of a novel fibrinolytic enzyme from culture supernatant of Cordyceps militaris

A novel fibrinolytic enzyme from Cordyceps militaris was produced by submerged culture fermentation, purified, and biochemically characterized. The enzyme was purified to homogeneity, with an overall yield of 4.0% and a specific activity of 1682 U/mg. The molecular weight and pI of the enzyme were 32 kDa and 9.3 ± 0.2, respectively. The optimal pH and temperature of the enzyme were 7.4 and 37 °C, respectively. The enzyme activity was inhibited by Fe(2+), phenylmethane sulfonyl fluoride (PMSF), aprotinin, and pepstatin but not by N-tosyl-L-phenylalanine chloromethyl ketone (TPCK) and ethylenediamine tetracetic acid (EDTA). Three internal peptides of the enzyme, APQALTVAAVGATWAR, EKNVGSTVNLLSYDGNK, and TDATSVLLDGYNVSAVNDLVAK, were obtained. The enzyme could hydrolyze fibrin(ogen) directly and cleave the α-chains more efficiently than β- and γ-chains, suggesting that it is a plasmin like protein. It degraded thrombin, which indicated that it can act as an anticoagulant and prevent thrombosis. Intravascular thrombosis is one of the major reasons of cardiovascular diseases. On the basis of these results, the purified enzyme can be developed as a natural agent for oral fibrinolytic therapy or prevention of thrombosis.

Biochemical characteristics of a fibrinolytic enzyme purified from a marine bacterium, Bacillus subtilis HQS-3

A fibrinolytic enzyme isolated from marine Bacillus subtilis HQS-3 was purified to electrophoretic homogeneity using ammonium sulphate precipitation, alkaline solution treatment, membrane concentration, dialysis, ion exchange, and gel filtration chromatography. SDS-PAGE and gel filtration chromatography showed that it was a monomeric protein with an apparent molecular weight of 26 kDa. The purified enzyme was active at pH 6.0-10.0 with an optimum pH of 8.0. It was stable at temperatures ranging from 25 to 37 °C, exhibiting maximum activity between 45 °C and 50 °C. The isoelectric point of the enzyme was 9.0-9.2, which was higher than those of other known fibrinolytic enzymes from Bacillus species. PMSF, EDTA, Cu(2+), Zn(2+), and Co(2+) inhibited the enzyme activity significantly. This enzyme did not cause hemolysis in vitro and preferred direct degradation of fibrin in the following order: α, β, and γ-γ chains. Thus, these results suggest that the marine-derived enzyme is a plasmin-like serine metalloprotease, which is distinct from other fibrinolytic enzymes from genus Bacillus.

Enhancement of the catalytic activity of a 27 kDa subtilisin-like enzyme from Bacillus amyloliquefaciens CH51 by in vitro mutagenesis

AprE51 from Bacillus amyloliquefaciens CH51 is a 27 kDa subtilisin-like protease with fibrinolytic activity. To enhance the catalytic activity of AprE51, two residues, Gly-169 and Ser-101, which, according to the three-dimensional structural model of subtilisin, are located in the P1 substrate-binding site and S3 subsite, respectively, were mutated by site-directed mutagenesis. Results of the mutational analysis showed that substitution of alanine for Gly-169 increased the fibrinolytic activity 1.4-fold. All four Ser-101 mutations, that is, replacements with arginine, leucine, lysine, and tryptophan, also increased the fibrinolytic activity up to 3.9-fold. The S101W mutant with a bulky side chain was more active than mutants with a positively charged or nonpolar small side chains. The fibrinolytic activity of the S101W mutant was further increased by error-prone polymerase chain reaction. The AprE51-6 mutant (S101W/G169A/V192A) had stronger fibrinolytic activity than the S101W mutant. Purified AprE51-6 had a 2.5-fold higher k(cat) and a 2.3-fold lower K(m), which resulted in a 6-fold increase in catalytic efficiency (k(cat)/K(m)) relative to that of wild-type AprE51. In addition, AprE51-6 showed a relatively broader pH range and increased thermostability as compared to AprE51.

Purification and characterization of a novel fibrinolytic enzyme from the polychaete, Neanthes japonica (Iznka)

A novel fibrinolytic enzyme from Neanthes japonica (Iznka), named NJF, was purified to electrophoretic homogeneity using ammonium sulfate precipitation, hydrophobic interaction, ion exchange and gel-filtration chromatography. NJF consisted of a single polypeptide chain with a molecular weight of 28-32 kDa, which was determined by MALDI-TOF mass spectrum and SDS-PAGE. The isoelectric point of NJF determined by isoelectric focusing electrophoresis (IEF) was 4.4, and the maximum activity of the enzyme was observed at 60 degrees C and pH 9.0. The cleavage speed of fibrinogen by NJF affected the Aalpha-chain first, followed by the Bbeta-chain and finally the gamma-chain. NJF activity was strongly inhibited by PMSF, indicating that it is a serine protease. Partial amino-acid sequences of its fragments were different from those of other known fibrinolytic enzymes. N. japonica may thus represent a potential source of new therapeutic agents to treat thrombosis.