Arterial thrombosis is the underlying cause of a wide variety of cardiovascular diseases including myocardial infarction. All the currently used thrombolytic agents are plasminogen activators, which are very efficient in restoring the blood flow. They can convert plasminogen into plasmin and thus degrade fibrin.Despite the widespread use of established thrombolytic agents such as streptokinase, t-PA and u-PA, all these agents suffer from a number of inadequacies including resistance to reperfusion, occurrence of coronary reocclusion and bleeding complications. The quest continues for plasminogen activators with higher potency, specific thrombolytic activity, fibrin selectivity and longer half-life time. The recent progress in the protein engineering of plasminogen activators, including t-PA, u-PA, streptokinase, staphylokinase and other novel plasminogen activators, was presented in this article.We can conclude that the new generation of thrombolytic agents showed considerable potential with regard to improving the efficacy of thrombolytic therapy, and these progresses were based on the detailed understanding of the relationship between structure and function of thrombolytic agents.However, the risk of intracranial bleeding remains problematic and need more researches on the modification of thrombolytic agents.

Arterial thrombosis is the underlying cause of a wide variety of cardiovascular diseases including myocardial infarction. All the currently used thrombolytic agents are plasminogen activators, which are very efficient in restoring the blood flow. They can convert plasminogen into plasmin and thus degrade fibrin. Despite the widespread use of established thrombolytic agents such as streptokinase, t-PA and u-PA, all these agents suffer from a number of inadequacies including resistance to reperfusion, occurrence of coronary reocclusion and bleeding complications. The quest continues for plasminogen activators with higher potency, specific thrombolytic activity, fibrin selectivity and longer half-life time. The recent progress in the protein engineering of plasminogen activators, including t-PA, u-PA, streptokinase, staphylokinase and other novel plasminogen activators, was presented in this article. We can conclude that the new generation of thrombolytic agents showed considerable potential with regard to improving the efficacy of thrombolytic therapy, and these progresses were based on the detailed understanding of the relationship between structure and function of thrombolytic agents. However, the risk of intracranial bleeding remains problematic and need more researches on the modification of thrombolytic agents.

GHRP-scu-PA-32K cDNA was obtained by in vitro site-directed-mutagenesis to insert oligonucleotide sequence (GGTCATAGGCCT) encoding tetrapeptide Gly-His-Arg-Pro into scu-PA-32K gene at site just preceding the amino-terminal residue(Leu¹). The mutant cDNA was cloned in pCM-β-neo expression vector and co-transformed CHO-DHFR^- cells together with pCM-dhfr. The stable expression cell line was selected. Expression level of the line cultured in serum-free medium was 580IU/106 cell/24h. The product expressed was purified by Zn²⁺-Sepharose affinity chromatography. The apparent molecular weight of purified GHRP-scu-PA-32K was 33kD by SDS-PAGE and mass spectrometry and its specific activity was 150000IU/mg protein, according to fibrin plate determination. The affinity for fibrin of GHRP-scu-PA-32K was 4.5 times higher than that of scu-PA-32K.

Recent developments on protein engineering of some related proteins in our research are introduced. Specificity change, antiautolysis and role of less conserved disulfide bonds of trypsin are demonstrated. Function of single domain and multi-copied domains of metallothionein is explained. Studies on intra-A chain disulfide bond and C-peptide of insulin, chimera of prourokinase and tissue-type plasminogen activator, mutation of plasminogen activator inhibitor-1, and RGD-containing proteins are also described.

Recent developments on protein engineering of some related proteins in our research are introduced. Specificity change, antiautolysis and role of less conserved disulfide bonds of trypsin are demonstrated. Function of single domain and multi-copied domains of metallothionein is explained. Studies on intra-A chain disulfide bond and C-peptide of insulin, chimera of prourokinase and tissue-type plasminogen activator, mutation of plasminogen activator inhibitor-1, and RGD-containing proteins are also described.