Summary
Amino acid sequences of two anticoagulant serine fibrinogenases – α- and β-fibrinogenase (VLAF and VLBF) from Vipera lebetina venom have been deduced from the cDNA sequences encoding the enzymes. The mature protein sequences of 234 amino acids (VLAF) and 233 amino acids (VLBF) exhibit significant similarity with other snake venom serine proteinases. Both enzymes contain the catalytic triad His57, Asp102, Ser195, and twelve conserved cysteines forming six disulfide bridges. Unlike typical trypsin-like serine proteinases, they lack the third aspartate, Asp189 which is replaced by Gly189. VLBF is a typical representative of arginine esterases – β-fibrinogenases. α-Fibrinogenase, VLAF, is unique among snake venom serine proteinases with homologous structure. Until now there is no evidence of the anticoagulant serine enzymes degrading fibrinogen α-chain only and lacking esterolytic activity.
Parts of this paper were presented at the 17th International Fibrinogen Workshop of the International Fibrinogen Research Society (IFRS) held in Munich, Germany, September, 2002.
The sequence data of Vipera lebetina mRNA for α- and β-fibrinogenase have been deposited in the GenBank database under accession numbers AF528193 (VLAF) and AF536235 (VLBF).
Keywords
α-Fibrinogenase - β-fibrinogenase - serine proteinase - snake venom - cDNA cloning
