Hementerin

Hementerin is a metalloprotease found in the saliva of a hematophagous leech, Haementeria depressa, which is responsible for the anticoagulant property of the animal's bite to prolong blood sucking from the host. It was discovered in 1955 at the Butantan Institute, in São Paulo, Brazil, by Gastão Rosenfeld and collaborators.

Mechanism of Action

Hementerin is a protease, i.e., it carries out an enzymatic cleaving of a plasma protein involved in rapid blood coagulation called fibrinogen. The absence of a significant amount of plasma fibrinogen retards coagulation, thus it is a naturally occurring anticoagulant. Hementerin breaks the alpha (FGA), gamma (FGG) and beta (FGB) chains, by degrading cross-linked fibrin. It has no degrading action on amide, plasminogen and casein. In addition, hementerin inhibits platelet aggregation induced by collagen via the activation of a nitridergic pathway. Inhibition is probably achieved by enhanced nitric oxide synthase activity. Calcium is a cofactor (ligand) in this activity. The fibrinolytic activity is inhibited by EDTA, a metal chelator agent, which removes zinc from the molecule.

Molecular Composition

Hementerin is a protein with 30 aminoacids, in the following sequence: XTLSEPEPTC SIEYFRYQAI EDCEYSISVK.

References

Hementerin. UNIPROT. Last modified March 21, 2012. Version 4.
Chudzinski-Tavassi A.M., Kelen E.M., de Paula Rosa A.P., Loyau S., Sampaio C.A., Bon C., Angles-Cano E. Fibrino(geno)lytic properties of purified hementerin, a metalloproteinase from the leech Haementeria depressa. Thromb. Haemost. 80:155-160(1998). [PubMed: 9684802] Abstract
Chudzinski-Tavassi A.M., Bermej E., Rosenstein R.E., Faria F., Sarmiento M.I., Alberto F., Sampaio M.U., Lazzari M.A.Nitridergic platelet pathway activation by hementerin, a metalloprotease from the leech Haementeria depressa. Biol. Chem. 384:1333-1339(2003). [PubMed: 14515997] Abstract
Rosenfeld G., Hampe O.G., Kelen E.M.A. Coagulant and fibrinolytic activity of animal venoms; determination of coagulant and fibrinolytic index of different species. Memórias do Instituto Butantan ;29:143-163, 1959.

Hydrolase: proteases (EC 3.4)

3.4.11-19: Exopeptidase

3.4.11	Aminopeptidase Alanine Arginyl Aspartyl Cystinyl Leucyl Glutamyl Methionyl 1 2 O

3.4.13	Dipeptidase 1 2 3

3.4.14	Dipeptidyl peptidase Cathepsin C Dipeptidyl peptidase-4 Tripeptidyl peptidase Tripeptidyl peptidase I Tripeptidyl peptidase II

3.4.15	Angiotensin-converting enzyme

3.4.16	Serine type carboxypeptidases: Cathepsin A DD-transpeptidase

3.4.17	Metalloexopeptidases Carboxypeptidase A A2 B C E Glutamate II

Other/ungrouped	Metalloexopeptidase

3.4.21-25: Endopeptidase

Other/ungrouped: Amyloid precursor protein secretase

3.4.99: Unknown

Staphylokinase

Enzymes

Activity	Active site Binding site Catalytic triad Oxyanion hole Enzyme promiscuity Catalytically perfect enzyme Coenzyme Cofactor Enzyme catalysis Enzyme kinetics Lineweaver–Burk plot Michaelis–Menten kinetics

Regulation	Allosteric regulation Cooperativity Enzyme inhibitor

Classification	EC number Enzyme superfamily Enzyme family List of enzymes

Types	EC1 Oxidoreductases (list) EC2 Transferases (list) EC3 Hydrolases (list) EC4 Lyases (list) EC5 Isomerases (list) EC6 Ligases (list)

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