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A protease is an enzyme that catalyzes proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of new protein products. They do this by cleaving the peptide bonds within proteins by hydrolysis, a reaction where water breaks bonds. Proteases are involved in numerous biological pathways, including digestion of ingested proteins, protein catabolism, and cell signaling.
Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The process of coagulation involves activation, adhesion and aggregation of platelets, as well as deposition and maturation of fibrin.
Disseminated intravascular coagulation (DIC) is a condition in which blood clots form throughout the body, blocking small blood vessels. Symptoms may include chest pain, shortness of breath, leg pain, problems speaking, or problems moving parts of the body. As clotting factors and platelets are used up, bleeding may occur. This may include blood in the urine, blood in the stool, or bleeding into the skin. Complications may include organ failure.
Fibrin is a fibrous, non-globular protein involved in the clotting of blood. It is formed by the action of the protease thrombin on fibrinogen, which causes it to polymerize. The polymerized fibrin, together with platelets, forms a hemostatic plug or clot over a wound site.
Prothrombin is encoded in the human by the F2-gene. It is proteolytically cleaved during the clotting process by the prothrombinase enzyme complex to form thrombin.
Factor XIII, or fibrin stabilizing factor, is a plasma protein and zymogen. It is activated by thrombin to factor XIIIa which crosslinks fibrin in coagulation. Deficiency of XIII worsens clot stability and increases bleeding tendency.
Hementin is an anticoagulant protease from the salivary glands of the giant Amazon leech. Hementin is a calcium-dependent protease with a molecular weight of 80–120 kDa, and it contains 39 amino acid sequences. Hementin is present in both the anterior and posterior salivary glands, however it is mostly produced from certain cells in the anterior glands. The secretion of hementin is limited to the lumen of the proboscis, which the Amazon leech inserts into the host to suck blood. Hementin dissolves platelet-rich blood clots and lets the blood flow through the proboscis. Hementin is able to dissolve a type of blood clots that cannot be dissolved by other compounds, such as streptokinase and urokinase.
Disintegrins are a family of small proteins from viper venoms that function as potent inhibitors of both platelet aggregation and integrin-dependent cell adhesion.
Kallikreins are a subgroup of serine proteases, enzymes capable of cleaving peptide bonds in proteins. In humans, plasma kallikrein has no known paralogue, while tissue kallikrein-related peptidases (KLKs) encode a family of fifteen closely related serine proteases. These genes are localised to chromosome 19q13, forming the largest contiguous cluster of proteases within the human genome. Kallikreins are responsible for the coordination of various physiological functions including blood pressure, semen liquefaction and skin desquamation.
Kininogens are precursor proteins for kinins, biologically active polypeptides involved in blood coagulation, vasodilation, smooth muscle contraction, inflammatory regulation, and the regulation of the cardiovascular and renal systems.
Ancrod is a defibrinogenating agent derived from the venom of the Malayan pit viper. Defibrinogenating blood produces an anticoagulant effect. Ancrod is not approved or marketed in any country. It is a thrombin-like serine protease.
The thrombin time (TT), also known as the thrombin clotting time (TCT), is a blood test that measures the time it takes for a clot to form in the plasma of a blood sample containing anticoagulant, after an excess of thrombin has been added. It is used to diagnose blood coagulation disorders and to assess the effectiveness of fibrinolytic therapy. This test is repeated with pooled plasma from normal patients. The difference in time between the test and the 'normal' indicates an abnormality in the conversion of fibrinogen to fibrin, an insoluble protein.
Batroxobin, also known as reptilase, is a snake venom enzyme with Venombin A activity produced by Bothrops atrox and Bothrops moojeni, venomous species of pit viper found east of the Andes in South America. It is a hemotoxin which acts as a serine protease similarly to thrombin, and has been the subject of many medical studies as a replacement of thrombin. Different enzymes, isolated from different species of Bothrops, have been called batroxobin, but unless stated otherwise, this article covers the batroxobin produced by B. moojeni, as this is the most studied variety.
Ecarin is an enzyme that is derived from the venom of the Indian saw-scaled viper, Echis carinatus, It is the primary reagent in the Ecarin clotting time test.
Venom-induced consumption coagulopathy (VICC) is a medical condition caused by the effects of some snake and caterpillar venoms on the blood. Important coagulation factors are activated by the specific serine proteases in the venom and as they become exhausted, coagulopathy develops. Symptoms are consistent with uncontrolled bleeding. Diagnosis is made using blood tests that assess clotting ability along with recent history of envenomation. Treatment generally involves pressure dressing, confirmatory blood testing, and antivenom administration.
Cerastocytin is a thrombin-like serine protease in snake venom.
Coagulin is a gel-forming protein of hemolymph that hinders the spread of bacterial and fungal invaders by immobilizing them. It is produced in the coagulogen form before being cleaved into the active form through a serine proteinase cascade. It has been most extensively studied in horseshoe crabs. It has also been produced by other organisms, such as Bacillus coagulans I4 in a plasmid location. In human medicine, coagulation of coagulin is the basis of detection of bacterial endotoxin through the Limulus amebocyte lysate test for parenteral medications.
Snake venom factor V activator is an enzyme. This enzyme catalyses the following chemical reaction
Penicillopepsin is an enzyme. This enzyme catalyses the following chemical reaction
Atrolysin A is an enzyme that is one of six hemorrhagic toxins found in the venom of western diamondback rattlesnake. This endopeptidase has a length of 419 amino acid residues. The metalloproteinase disintegrin-like domain and the cysteine-rich domain of the enzyme are responsible for the enzyme's hemorrhagic effects on organisms via inhibition of platelet aggregation.
References
- ↑ Nolan C, Hall LS, Barlow GH (1976). "Ancrod, the coagulating enzyme from Malayan pit viper (Agkistrodon rhodostoma) venom". Part B: Proteolytic Enzymes. Methods in Enzymology. Vol. 45. pp. 205–13. doi:10.1016/s0076-6879(76)45020-6. ISBN 978-0-12-181945-3. PMID 1011992.
- ↑ Stocker K, Barlow GH (1976). "The coagulant enzyme from Bothrops atrox venom (Batroxobin)". Part B: Proteolytic Enzymes. Methods in Enzymology. Vol. 45. pp. 214–23. doi:10.1016/s0076-6879(76)45021-8. ISBN 978-0-12-181945-3. PMID 1011993.
- ↑ Markland FS, Kettner C, Schiffman S, Shaw E, Bajwa SS, Reddy KN, Kirakossian H, Patkos GB, Theodor I, Pirkle H (March 1982). "Kallikrein-like activity of crotalase, a snake venom enzyme that clots fibrinogen". Proceedings of the National Academy of Sciences of the United States of America. 79 (6): 1688–92. Bibcode:1982PNAS...79.1688M. doi: 10.1073/pnas.79.6.1688 . PMC 346045 . PMID 7043462.
- ↑ Simmons G, Bundalian M, Theodor I, Martinoli J, Pirkle H (November 1985). "Action of crotalase, an enzyme with thrombin-like and kallikrein-like specificities, on tripeptide nitroanilide derivatives". Thrombosis Research. 40 (4): 555–61. doi:10.1016/0049-3848(85)90292-0. PMID 2934864.
- ↑ Itoh N, Tanaka N, Funakoshi I, Kawasaki T, Mihashi S, Yamashina I (June 1988). "Organization of the gene for batroxobin, a thrombin-like snake venom enzyme. Homology with the trypsin/kallikrein gene family". The Journal of Biological Chemistry. 263 (16): 7628–31. doi: 10.1016/S0021-9258(18)68544-8 . PMID 3163691.
- ↑ Bell WR, Jr (1997). "Defibrinogenating enzymes". Drugs. 54 (Suppl 3): 18–30, discussion 30–1. doi:10.2165/00003495-199700543-00005. PMID 9360849. S2CID 25006039.
- ↑ Kelton, JG; Smith, JW; Moffatt, D; Santos, A; Horsewood, P (1999). "The interaction of ancrod with human platelets". Platelets. 10 (1): 24–9. doi:10.1080/09537109976310. PMID 16801067.
- ↑ Hao Z, Liu M, Counsell C, Wardlaw JM, Lin S, Zhao X (March 2012). "Fibrinogen depleting agents for acute ischaemic stroke". The Cochrane Database of Systematic Reviews (3): CD000091. doi:10.1002/14651858.CD000091.pub2. PMC 11503785 . PMID 22419274.
- ↑ Vu, TT; Stafford, AR; Leslie, BA; Kim, PY; Fredenburgh, JC; Weitz, JI (7 June 2013). "Batroxobin binds fibrin with higher affinity and promotes clot expansion to a greater extent than thrombin". The Journal of Biological Chemistry. 288 (23): 16862–71. doi: 10.1074/jbc.M113.464750 . PMC 3675619 . PMID 23612970.
