Interaction of hementin with fibrinogen and fibrin
Biochemistry review published in Blood Coagul Fibrinolysis (1991)
Abstract
The giant Amazon leech Haementeria ghilianii manufactures blood anticoagulant which is present in the posterior and anterior salivary glands. The mechanism of blood anticoagulation by Haementeria ghilianii is completely different from that used by Hirudo medicinalis. The anticoagulant is mostly associated with a fibrinogen-degrading proteinase, hementin. However, other inhibitors of blood coagulation are also present in the salivary glands. The salivary gland extract inhibits platelet aggregation that is mostly attributable to the degradation of fibrinogen. Hementin purified by various methods has a molecular weight in the range of 80,000-120,000 and appears to be a metalloproteinase that is regulated by calcium ions. The enzyme degrades both fibrinogen and fibrin. The Michaelis constant for human fibrinogen is 1 microM. The cleavage of the isolated chains of fibrinogen is inefficient implying that the native conformation of the substrate may play a role in the recognition mechanism. The pattern of fibrinogen degradation by hementin resembles that caused by plasmin since products analogous to fragments Y, D and E are generated. However, the unique action of hementin on fibrinogen is in the initial proteolytic attack in the coiled-coil connector region while proteolysis of the alpha-chain is very slow. In consequence, unique fibrinogen fragments are formed that contain the entire COOH-terminus of the alpha-chain. The mechanism of blood anticoagulation by hementin is very efficient since the cleavage of only three peptide bonds in the fibrinogen molecule disassembles its bivalent structure and renders it non-functional.
Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.
Resumen
Hementin, an 80–120 kDa calcium-dependent metalloproteinase from Haementeria ghilianii salivary glands, degrades fibrinogen and fibrin via unique cleavage in the coiled-coil connector region — a mechanism distinct from both hirudin (Hirudo) and plasmin.
Por qué esto importa para la hirudoterapia
El resumen caracteriza la hementina, una metaloproteinasa degradadora de fibrinógeno (peso molecular 80.000–120.000) producida en las glándulas salivales de la sanguijuela gigante amazónica Haementeria ghilianii, cuyo mecanismo anticoagulante difiere por completo del de Hirudo medicinalis. Informa sobre la actividad proteolítica regulada por calcio de la hementina tanto sobre el fibrinógeno como sobre la fibrina (Km para fibrinógeno humano de 1 µM), su ataque inicial a la región conectora en superhélice del fibrinógeno y la generación de fragmentos únicos que retienen el extremo COOH de la cadena alfa, con la escisión de solo tres enlaces peptídicos que vuelven al fibrinógeno no funcional. Para la ASH, esto es directamente relevante para comprender la diversidad molecular de los anticoagulantes derivados de sanguijuelas. El resumen presenta datos de caracterización bioquímica; no se realizan afirmaciones clínicas ni terapéuticas in vivo.
Citación
Interaction of hementin with fibrinogen and fibrin.
Budzynski AZ · Blood coagulation & fibrinolysis : an international journal in haemostasis and thrombosis, 1991
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Añadido a la biblioteca ASH: May 26, 2026 · Última actualización del sitio: 18 de junio de 2026