Serine proteases activator

Factor XI. Factor XI is a Hver-synthesized glycoprotein that circulates in a zymogen form as a dimer. It is converted to its active serine protease form by Factor Xlla in the presence of high molecular weight kininogen. Calcium is not required for this activation step. 

Plasmin, a serine protease (83 kDa), can degrade fibrin, and its degradation products (FDP) are soluble in the blood. Plasmin is formed from its proenzyme (zymogen, precursor), plasminogen (92 kDa), synthesized by the liver, and secreted into the blood circulation, where its concentration is 2 pM. Plasminogen is converted to plasmin by plasminogen activators (serine proteases). 

Urokinase-type plasminogen activator (uPA, urokinase) is synthesized by endothelial and tumor cells as a single-chain glycoprotein (scuPA) without catalytic activity. When it is converted to a two-chain protein (tcuPA) by plasmin, an active serine protease center develops, which activates plasminogen. Thus, uPA (55 kDa) results in the amplification of fibrinolysis. 

The protease conformation of DegP is still elusive as crystallization of a substratelike inhibitor complex has failed and maintenance of a stably folded protein precludes long-term experimentation at elevated temperatures where it displays protease activity. We propose a profound rearrangement of the LA -L1-L2 loop triad into the canonical conformation of active serine proteases competent for substrate binding. This may be initiated by a collapse of the hydrophobic LA platforms and an enlargement of the hydrophobic contacts caused at high temperature. 

A range of chiral (ly)-proline derivatives, for example 211, have been shown to be active serine protease inhibitors and are active antivirals of human cytomegalovirus (HCMV) <2003JME4428>. 

Serpins were first identified as a set of proteins able to inhibit proteases. The name serpin is derived from this activity serine protease inhibitors . Heparin is a mixture of polysaccharides that bind to antithrombin in, inducing an allosteric change that greatly enhances its inhibition of thrombin synthesis. Some surgical patients, especially those receiving hip or heart valve replacements and those at risk of ischemic stroke (clots in the brain), are given heparin. 

Heparin acts as a catalyst for antithrombin III (AT III), increasing its activity by approximately a thousand times. Antithrombin III is a plasma enzyme that inactivates certain activated serine proteases of the coagulation cascade, most importantly activated factors II (thrombin) and X. The larger heparin species (found in unfractionated heparin) catalyzes the inactivation of activated factors II and X. In contrast, LMWH chiefly inactivates activated factor X. The final effect of both is systemic anticoagulation. Heparin also possesses inherent platelet-aggregating properties and may also induce the production of platelet-aggregating antibodies. Heparin can inhibit aldosterone synthesis. 

Viperidae endopeptidase, factor X activator, fibrinogenase, kininogenase, metalloproteinase, prothrombin activator, serine protease, thrombin-like enzyme... 

The TRADD or FADD domains bind to adapter proteins in the cytosol and together they form of a death inducing signaling complex (DISC). This complex recruits caspase-8, one of a family of calcium ion-activated serine proteases (caspases) which cleave polypeptides on the C-terminal side of their aspartate residues. DISC activates caspase-8 to activate a Bcl-2 activator, BID (Fig. 13.1 Oa). The resultant tBid fragment activates effector Bcl-2 proteins on the endoplasmic reticular membrane and mitochondrial outer membrane. 

Plasminogen Activator and the Transformed Phenotype In Vitro Studies -One protease which Increases in many cell types after neoplastic transformation is plasminogen activator (PA). The synthesis of PA may be elevated 50-300 fold after transformation. PA is an active serine protease which cleaves at arginine bonds. The enzyme can be inhibited by 1-32 isopropylfluorophosphate, nitrophenyl-guanldobenzoate, and benzamidine. 

Release of thrombin fi-om its inactive zymogen. Prothrombin (see), is the penultimate step in a series of reactions, each of which releases an active serine protease from an inactive precursor in the blood. It is an example of cascade regulation, in which each activated protease activates the next precursor down the line, increasing amounts of material being involved at each step (i.e. there is amplification). The clotting factors are listed in the Table. The assigned Roman numerals are historical, and the activated form is indicated by the subscript a (e.g. XII,). 

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