Defibrase

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Defibrase is a proteolytic enzyme with a single component. It can inhibit platelet aggregation, reduce vascular resistance, enhance red blood cell deformability, and improve microcirculation. It has been clinically used to treat acute cerebral infarction, unstable angina pectoris, venous thrombosis, hyperviscosity, etc., and has achieved good results. Defibrase can induce the release of tissue plasminogen activator (t-PA), and can enhance t-PA to promote fibrinase production. Reduce the activity of α2 plasminogen inhibitor and plasminogen activator inhibitor. Enhance the activity of active plasmin, degrade fibrinogen and shorten the dissolution time of euglobulin It also has the effects of reducing the viscosity of whole blood, inhibiting the sedimentation of red blood cells, enhancing the permeability and deformability of red blood cells, reducing vascular resistance, and inhibiting thrombosis.

Introductions

With the clarification of the clinical application and research value of snake venom thrombin-like enzymes, many researches have been carried out on the physicochemical and enzymatic properties of thrombin-like enzymes in the venom of the snake venom and the snake venom. Various studies have shown that both the cuspidae snake and the white eyebrow ventral snake are relatively rich in TLE content. Among them, the cuspidae snake venom contains several isoenzymes with thrombin-like effects. The molecular weights and isoelectric points reported in the literature are not the same. The reason for this phenomenon may be that the molecular weights reported in the literature are all determined by SDS-PAGE, the purity of the samples is inconsistent and the error of the measurement itself is caused. On the one hand, it may also be caused by biological differences caused by changes in different geographical environments and food intake, such as differences in glycosylation levels.

Biochemical properties

Defibrase is a typical thrombin-like enzyme. It is a proteolytic enzyme with serine as the active center. It can act on fibrinogen with high selectivity, but its effect on fibrinogen is more specific than thrombin. Thrombin can first cleave the 16 N-terminal peptide (FPA) of the fibrinogen α chain, thereby connecting the fibrin end to tail, and then cleave the 14 peptide N-terminal of the β chain (FPB), and the fibrin further laterally polymerizes In vivo coagulation factor ⅩⅢ then cross-links fibrin molecules in the form of peptide bonds to form insoluble fibrin. While most snake venom thrombins only act on one chain of fibrinogen, only a few snake venom thrombins can act on two chains. According to its mode of action on fibrinogen, it can be divided into FPA type, FPB type and FPAB type.

Study on the structure of defibrase

The study of the structure of defibrase is of key significance to many research fields such as understanding its substrate selectivity, the relationship between structure and biological activity, and the use of gene recombination technology for expression. At this stage, research on the structure of defibrase includes determination of amino acid sequence, determination of disulfide bond positions and glycosylation sites, deduction of enzyme active centers, and simulation of high-level structures. Domestic scholars have studied the structure of defibrase in Agkistrodonacutus and Agkistrodon acutus, two raw material sources for the production of defibrase for injection prescribed by the national drug standards. Total RNA was prepared from the venom gland of Agkistrodonacutus, amplified by PCR and then sequenced in two directions, and the corresponding amino acid sequence of the defibrase acutin was deduced. The experimental results show that acutin is composed of 233 amino acids and its amino acid sequence has a high degree of homology with the sequence structure of the ventral subfamily snake venom thrombin.

Pharmacological action and application

Defibrase can reduce the content of coagulation factor Ⅰ in plasma, resist platelet aggregation and reduce blood viscosity. Although it can release the α chain of coagulation factor Ⅰ, fibrin peptide A, but this peptide is easily hydrolyzed and eliminated by enzymes. The reduction of coagulation factor I is the main effect of anticoagulation; defibrase also converts plasminogen into plasmin, reduces blood viscosity, inhibits the aggregation of red blood cells and platelets, improves microcirculation, and dissolves thrombus. It is clinically used to treat thrombo-occlusive vasculitis, arterial embolism, cerebral embolism, transient ischemic attack (TIA), prevention and treatment of angina and myocardial infarction, and eliminate the state of hypercoagulability and high viscosity. It is also effective for sudden deafness caused by blood circulation disorders in the inner ear.