Cloning, purification and enzymatic assay of streptokinase gene from Streptococcus pyogenes in Escherichia coli

BACKGROUND: Streptokinase is an important therapeutic enzyme that acts as a fibrinolytic agent and use in the treatment of multi serious and life threatening diseases such as pulmonary embolism and acute myocardial infarction. METHODS: Cloning and extracellular expression of recombinant streptokinase from native Streptococcus pyogenes PTCC 1447 was done by fusing the gene coding for streptokinase to an efficient vector (pET15b) with NdeI and BamHI as restriction enzymes and T4 DNA ligase. Streptokinase activity was determined using synthetic chromogenic substrate S-2251. Purification was done under N-terminal 6x histidine tag complementation using affinity chromatography. RESULTS: the DNA and amino acid sequence alignments resulting from the BLAST search of streptokinase showed high sequence identity with the other strains of S. pyogenes. The recombinant enzyme was purified successfully showing high streptokinase activity. CONCLUSIONS: Despite several limitations, streptokinase has some advantages such as low cost, available microbial source, and higher half-life in comparison with many other fibrinolytic agents.