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Suramin interaction with human alpha-thrombin: inhibitory effects and binding studies
Robson Q Monteiro1, Patricia T Campana, Paulo A Melo
1Departamento de Bioquímica Médica, ICB/CCS, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil. robsonqm@bioqmed.ufrj.br
The International Journal of Biochemistry & Cell Biology
|June 19, 2004
Summary
Suramin, an antitrypanosomial drug, inhibits human alpha-thrombin activity by binding to two sites. Albumin reverses this inhibition, suggesting limited plasma effects and potential extra-vascular roles.
Area of Science:
- Biochemistry
- Pharmacology
- Molecular Biology
Background:
- Suramin is a hexasulfonated naphthylurea used as an antitrypanosomial agent and in cancer therapy.
- Alpha-thrombin plays a crucial role in blood coagulation and fibrinolysis.
Purpose of the Study:
- To investigate the interaction between suramin and human alpha-thrombin.
- To elucidate the inhibitory mechanism and binding characteristics of suramin on alpha-thrombin.
Main Methods:
- Enzyme kinetics (S-2238 hydrolysis, fibrinogen clotting)
- Isothermal titration calorimetry (ITC)
- Circular dichroism (CD) spectroscopy
- Fluorescence spectroscopy
Main Results:
- Suramin inhibits alpha-thrombin's catalytic activity (IC50 = 40 microM for S-2238, 20 microM for clotting).
- Inhibition is non-competitive, decreasing Vmax but not Km.
- Albumin (30 mg mL(-1)) completely reverses thrombin clotting inhibition.
- ITC revealed two distinct binding sites; CD showed tertiary structure changes.
- High ionic strength affects complex formation, indicating electrostatic interactions.
Conclusions:
- Suramin binds to alpha-thrombin, altering its structure and inhibiting its enzymatic activity.
- The inhibitory effect in plasma is likely limited due to albumin reversal.
- Suramin's biological activities may involve alpha-thrombin inhibition at extra-vascular sites.