Hementin

Hementin is an anticoagulant protease (fibrinogen lytic enzyme) from the salivary glands of the giant Amazon leech (Haementeria ghilianii). 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 gland. The secretion of the hementin is limited to the lumen of the proboscis, which the Amazon leech inserts into the host to suck the blood.[1] Hementin dissolves platelet-rich blood clots and lets the blood flow through the proboscis.[1] Hementin is able to dissolve a type of blood clots that cannot be dissolved by other compound, such as streptokinase and urokinase.

The processes of blood anticoagulation by hementin includes the degradation of fibrinogen.[2] It is capable of disrupting the function of fibrinogen, a glycoprotein responsible for blood clotting, by cleaving three peptide bonds in its structure. Hementin is also capable of segregating platelets by cleaving the fibrinogen cross-link amongst the platelets. Fibrinogen acts as a substrate for thrombin, which converts the protein into its functional form, fibrin. Cleavage of fibrinogen in its native conformation at AαAsn102-Asn103, BβLys130-Gln131, and ϓPro76-Asn77 yield three sets of products.[3] Hementin may also cause platelet deaggregation, although not under all circumstances.[4] Because of its anticoagulant effects, Hementin can be described as a hemostatic regulator.

References
  1. Sawyer, Roy (February 1991). "The Biological Function of Hementin in the Proboscis of the Leech Haementeria Ghilianii". Blood Coagulation & Fibrinolysis : An International Journal in Haemostasis and Thrombosis. DOI: 10.1097/00001721-199102000-00023 (1): 153–9. doi:10.1097/00001721-199102000-00023. PMID 1772983.
  2. "UniProtKB - Q7M3P9 (HTN_HAEGH)". UniProt.
  3. Budzynski, A. Z. (February 1991). "Interaction of hementin with fibrinogen and fibrin". Blood Coagulation & Fibrinolysis. 2 (1): 149–152. doi:10.1097/00001721-199102000-00022. ISSN 0957-5235. PMID 1772982.
  4. Zavalova, L. L.; Basanova, A. V.; Baskova, I. P. (2002). "Fibrinogen–Fibrin System Regulators from Bloodsuckers". Biochemistry (Moscow). 67 (1): 135–142. doi:10.1023/A:1013916601281. PMID 11841348.
  • Malinconico, SM; Katz, JB; Budzynski, AZ (January 1984). "Hementin: anticoagulant protease from the salivary gland of the leech Haementeria ghilianii". The Journal of Laboratory and Clinical Medicine. 103 (1): 44–58. PMID 6361187.
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