Complement and coagulation cascades

The complement system is a proteolytic cascade in blood plasma and a mediator of innate immunity, a nonspecific defense mechanism against pathogens. There are three pathways of complement activation: the classical pathway, the lectin pathway, and the alternative pathway. All of these pathways generate a crucial enzymatic activity that, in turn, generates the effector molecules of complement. The main consequences of complement activation are the opsonization of pathogens, the recruitment of inflammatory and immunocompetent cells, and the direct killing of pathogens. Blood coagulation is another series of proenzyme-to-serine protease conversions, culminating the formation of thrombin, the enzyme responsible for the conversion of soluble fibrinogen to the insoluble fibrin clot. Protease-activated receptors, such as those activated by thrombin, are members of G protein-coupled receptors and function as a mediator of innate immunity. The kallikrein-kinin system is an endogenous metabolic cascade, triggering of which results in the release of vasoactive kinins (bradykinin-related peptides). Kinin peptides are implicated in many physiological and pathological processes including the regulation of blood pressure and sodium homeostasis, inflammatory processes, and the cardioprotective effects of preconditioning. Source: [http://www.genome.jp/dbget-bin/www_bget?pathway:map04610 KEGG]

补体系统是存在于血液浆中的一系列蛋白水解级联反应，它是先天免疫的介质，对病原体的非特异性防御机制。补体激活存在三条途径：经典途径、凝集素途径和替代途径。这些途径均产生至关重要的酶促活性，进而生成补体的效应分子。补体激活的主要后果包括病原体的调理作用、炎症和免疫活性细胞的募集，以及对病原体的直接杀伤。血液凝固是一系列从前酶到丝氨酸蛋白酶的转化过程，最终形成凝血酶，该酶负责将可溶性纤维蛋白原转化为不溶性纤维蛋白凝块。由凝血酶等激活的蛋白酶激活受体属于G蛋白偶联受体，作为先天免疫的介质。激肽释放酶-激肽系统是一种内源性代谢级联反应，其触发导致血管活性激肽（如缓激肽相关肽）的释放。激肽肽类物质参与多种生理和病理过程，包括血压和钠稳态的调节、炎症过程以及预适应的心脏保护作用。来源：[http://www.genome.jp/dbget-bin/www_bget?pathway:map04610 KEGG]