MODERN CONCEPTS OF BIOCHEMISTRY OF BLOOD COAGULATION

Аннотация

The blood coagulation system is a complex biochemical process that stops bleeding and protects the body from excessive blood loss. This process involves a cascade of reactions involving plasma proteins, cells, and calcium ions. This system functions in close relationship with the system of anticoagulation and fibrinolysis, providing a balance between the formation and destruction of blood clots. Key words: blood coagulation, hemostasis, platelets, coagulation factors, fibrinolysis, anticoagulants, thrombin, fibrinogen, calcium, coagulation cascade. СОВРЕМЕННЫЕ ПРЕДСТАВЛЕНИЯ О БИОХИМИИ СВЕРТЫВАНИЯ КРОВИ Аннотация. Система свертывания крови — сложный биохимический процесс, останавливающий кровотечение и защищающий организм от чрезмерной кровопотери. Этот процесс включает каскад реакций с участием плазменных белков, клеток и ионов кальция. Эта система функционирует в тесной взаимосвязи с системой антикоагуляции и фибринолиза, обеспечивая баланс между образованием и разрушением тромбов. Ключевые слова: свертывание крови, гемостаз, тромбоциты, факторы свертывания, фибринолиз, антикоагулянты, тромбин, фибриноген, кальций, каскад свертывания. Blood coagulation is a complex network of biochemical reactions that is activated when the integrity of the vascular system is disrupted. The purpose of clotting is to control the local transition of blood plasma from a liquid state to a jelly-like state and, as a result, stop bleeding. Any disturbances in the delicate balance of this system lead to severe consequences associated with thrombosis or bleeding. The purpose of this first part of our review is to introduce the reader to modern concepts of coagulation biochemistry. The second part will examine the mechanisms of its regulation, and the third will describe attempts to apply these fundamental concepts to solving practical problems in the diagnosis and treatment of hemostasis disorders. The main components of the blood coagulation system 1. Blood coagulation factors are protein compounds presented in the form of inactive enzymes (prozymogens) that are activated when the coagulation cascade is triggered. There are 13 main coagulation factors, indicated by Roman numerals (I – XIII). 769 ResearchBib IF - 11.01, ISSN: 3030-3753, Volume 2 Issue 3 2. Cellular elements – platelets, vascular endothelial cells and erythrocytes involved in the process of aggregation and formation of the primary thrombus. 3. Calcium (Ca2⁺) is an important co-factor for the activation of several coagulation factors. 4. Phospholipids are membrane components of cells that ensure the assembly of enzyme complexes of the coagulation system. Biochemical mechanism of blood clotting The process of blood clotting is a cascade of reactions that includes three main phases: 1. Initiation (launch) – either the external or internal pathway of coagulation is activated. The external pathway begins with the release of tissue factor (factor III), which interacts with factor VIIa and calcium ions, activating factor X. The internal pathway includes the activation of factor XII upon contact with the damaged surface, which triggers the sequential activation of factors XI, IX and VIII. 2. Coagulation phase – activated factor X (Xa), together with factor V, calcium and phospholipids, forms prothrombinase, which converts prothrombin (factor II) into thrombin. 3. Formation of a fibrin clot – thrombin breaks down fibrinogen (factor I) to fibrin, which polymerizes and stabilizes under the action of factor XIIIa, forming a durable thrombus. The local transition of blood plasma from a liquid state to a jelly-like state is caused by the activation of the coagulation cascade and the formation of a fibrin clot. This process begins at the site of the vessel injury and includes the following steps: Activation of platelets, which secrete factors that promote coagulation. The formation of prothrombinase, which catalyzes the conversion of prothrombin into thrombin. Thrombin activates fibrinogen, which is converted into insoluble fibrin filaments. Fibrin filaments form a mesh structure that traps blood cells and plasma proteins, which leads to the transition of the liquid into a jelly-like state. Stabilization of the clot under the action of factor XIII, which strengthens intermolecular bonds in fibrin. This process prevents blood loss and promotes healing of the damaged vessel. Modern concepts of the biochemistry of blood coagulation Modern research in the field of blood coagulation has revealed new mechanisms of regulation of the coagulation system. Among the key aspects are: The role of microparticles – extracellular vesicles secreted by platelets and endothelial cells, play an important role in the activation of coagulation. Genetic factors – mutations in the genes encoding clotting factors (for example, Leiden factor V) can lead to hypercoagulation and an increased risk of thrombosis. 770 ResearchBib IF - 11.01, ISSN: 3030-3753, Volume 2 Issue 3 The effect of inflammation – inflam