On the occurrence of thrombin-like enzymes in mosquitoes.
A thrombin-like enzyme has been identified in mosquitoes and partially purified. The enzyme preparation displays on SDS gel electrophoresis a major protein band of about 22 kDa and one minor of about 28 kDa. The enzyme preparation cleaves a synthetic substrate (S-2238) for thrombin with Km 113 mumol/L (as compared to 3 mumol/L for thrombin). The enzyme clots fibrinogen and plasma. During activation of fibrinogen, fibrinopeptide A (but scarcely fibrinopeptide B) is released. The enzyme is not inhibited by hirudin and activates (if at all) factor XIII differently from thrombin. Predominantly gamma-dimers are formed in the cross linking process. As compared to thrombin a larger extent of activation is required to induce gelation (clotting) by the mosquito enzyme. At a given clotting time the enzyme produces tighter gel structures than thrombin. In its action the enzyme resembles the snake venom enzyme, batroxobin.
Bark
N
N
Department Medical Biophysics, Karolinska Institutet, Stockholm, Sweden. Niklas.Bark/mbb.ki.se
Blombäck
B
B
Fatah
K
K
D000330:Aedes / Q000201:enzymology*; D000645:Ammonium Sulfate; D000818:Animals; D005591:Chemical Fractionation; D002850:Chromatography, Gel; D000431:Ethanol; D005342:Fibrinolysis; D008970:Molecular Weight; D009391:Nephelometry and Turbidimetry; D013917:Thrombin / Q000302:isolation & purification*
D000431:Ethanol; D013917:Thrombin; D000645:Ammonium Sulfate