Abstract: The present invention discloses the thrombolytic therapy by t-PA or CT-b for the treatment of the acute myocardial infarction. A chimeric truncated form of t-PA or CT-b is designed and expressed in Pichia pastoris. The CT-b includes desmoteplase finger domain, human EGF, kringle 1 and protease domain. The human kringle 2 domain is removed in CT-b to make it structurally and functionally similar to desmoteplase. The fibrin specificity or the catalytic activity is 1560 times more in the presence of fibrin. The CT-b also shows 1.2 fold higher resistances to PAI-1 enzyme. As the kringle domain is considered as one of the binding sites for PAI-1, the deletion along with amino acid substitution in protease domain contributes to prolonged half-life. Further the activity of the CT-b is intact after exposure to PAI-1. In other words CT-b is inhibited 44% less than t-PA by PAI-1 enzyme, demonstrating improved half life.

Abstract: The present invention discloses a thrombolytic therapy for acute myocardial infarction by t-PA. A chimeric truncated form of t-PA is designed and expressed in Pichia pastoris. The new variant t-PA comprises of a finger domain of Desmoteplase, an epidermal growth factor (EGF) domain, a kringle 1 domain, a kringle 2 domain in which the lysine binging site is deleted, and a protease domain where the four amino acids lysine 296, arginine 298, arginine 299, and arginine 304 are substituted by aspartic acid. The chimeric t-PA shows has increased activity of 14 fold in presence of fibrin. The t-PA shows 10-fold increased potency than commercially available full length t-PA (Actylase®) and provides 1.2 fold greater affinity to fibrin. Further a residual activity of only 68% is observed after incubation of Actylase® with PAI-1 and 91% residual activity for t-PA. The t-PA variant is acceptable plasminogen activator with enhanced biochemical properties.