Journal of Industrial Microbiology & Biotechnology

, Volume 40, Issue 1, pp 151–158

Pitfalls in screening streptococci for retrieving superior streptokinase (SK) genes: no activity correlation for streptococcal culture supernatant and recombinant SK


  • Malihe Keramati
    • Microbiology DepartmentPasteur Institute of Iran
    • Hepatitis and AIDS DepartmentPasteur Institute of Iran
    • Hepatitis and AIDS DepartmentPasteur Institute of Iran
  • Mohammad Mehdi Aslani
    • Microbiology DepartmentPasteur Institute of Iran
  • Fatemeh Motevalli
    • Hepatitis and AIDS DepartmentPasteur Institute of Iran
  • Shohreh khatami
    • Biochemistry DepartmentPasteur Institute of Iran
  • Arash Memarnejadian
    • Hepatitis and AIDS DepartmentPasteur Institute of Iran
Genetics and Molecular Biology of Industrial Organisms

DOI: 10.1007/s10295-012-1205-y

Cite this article as:
Keramati, M., Roohvand, F., Aslani, M.M. et al. J Ind Microbiol Biotechnol (2013) 40: 151. doi:10.1007/s10295-012-1205-y


Streptokinase (SK), the heterogeneous protein family secreted by some groups of β-hemolytic streptococci (βHS), is a plasminogen activator and well-known drug for thrombolytic therapy. Differences in plasminogen activation property of streptococcal culture supernatants (SCS) have been traditionally used to identify superior producer strains and SK genes (skc) for recombinant SK (rSK) production. However, the role of SK heterogeneity and whether SK activities in SCS correlate with that of their corresponding rSK is a matter of debate. To address these concerns, SCS of nine group C streptococci (GCS) screened among 252 βHS clinical isolates were compared for plasminogen activation using S-2251 chromogenic assay. The GCS (Streptococcus equisimilis) showing the highest (GCS-S87) and lowest (GCS-S131) activities were selected for PCR-based isolation of skc, cloning and rSK production in Escherichia coli. The 6×His-tagged rSK proteins were purified by NI–NTA chromatography, analyzed by SDS-PAGE and Western blotting and their activities were determined. While SCS of GCS-S87 and GCS-S131 showed different plasminogen activations (95 and 35 %, respectively) compared to that of the reference strain (GCS-9542), but interestingly rSK of all three strains showed close specific activities (1.33, 1.70, and 1.55 × 104 IU mg−1). Accordingly, SKS87 and SKS131 had more than 90 % sequence identity at the amino acids level compared to SK9542. Therefore, SK heterogeneity by itself may not contribute to the differences in plasminogen activation properties of SCS and evaluation of this activity in SCS might not be a proper assay for screening superior skc.


Plasminogen activationPlasmin amidolytic substrateRecombinant streptokinaseStreptococcus equisimilis

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© Society for Industrial Microbiology and Biotechnology 2012