Expression and characterization of a fibrinogenolytic enzyme from horsefly salivary gland

Enzymes from various natural resources are valuable in management of thrombosis. Blood-sucking arthropods are one of these resources because they have a wide array of anti-hemostasis molecules in their salivary gland. However, it is difficult to purify enough protein samples from the salivary glands for pharmacological studies. In this work, a fibrinogenolytic enzyme (tablysin 2) identified from salivary glands of the horsefly Tabanus yao was expressed in Escherichia coli to further study its biological activities. The primary structure of tablysin 2 showed significant domain similarity to arthropod proteins from the antigen 5 family containing SCP domain, whose biological functions are poorly understood. Tablysin 2 cleaved the Aα and part of Bβ chains of fibrinogen and did not affect γ chain and fibrin. It inhibited platelet aggregation induced by ADP. It did not directly induce hemorrhage or activate plasminogen. The fibrinogenolytic activity of tablysin 2 provides a clue for the functions of antigen 5-related proteins in other haematophagous arthropods. This work demonstrate a method of expression of arthropod salivary proteins which are difficult to obtain from natural resources for further functional studies.