ABSTRACT
Thrombolytic therapy with plasminogen activators (PAs) is now performed routinely for the
treatment of acute myocardial infarction. However, thrombolytic agents such as streptokinase
(SK), tissue-type plasminogen activator (t-PA), and urokinase-type plasminogen activators
(u-PA) exhibit various shortcomings relative to their pharmacodynamic and pharmacokinetic
characteristics and additionally may cause life-threatening side effects. With the aim of creating
an improved fibrinolytic agent in mind, we have cloned and expressed the plasminogen activators
from the saliva of the vampire bat Desmodus rotundus, originally described by Hawkey (1966).
Four Desmodus rotundus salivary plasminogen activators (DSPAs) were identified which-like
t-PA and u-PA-are composed of various conserved domains known from related proteins.
DSPAa1 and DSPAa2 exhibit the structural formula finger (F), EGF (E), kringle (K), protease (P), DSPAb, and the g formulas EKP and KR, respectively. Subtle sequence differences and data from Southern blot hybridization analysis indicate that the four enzymes are coded by four
different genes and are not generated by differential splicing of a single primary transcript. A
preliminary biochemical and pharmacological analysis indicated that DSPAa1 exhibited the most favorable profile and was, therefore, chosen for further study. A recombinant CHO-cell line for
the production of DSPA and a purification protocol were established to obtain material that
fulfilled the specifications for preclinical and clinical development.
