Indirect active-site titration of plasminogen activators

Area of Science:

• Biochemistry
• Enzymology
• Analytical Chemistry

Background:

• Tissue plasminogen activator (TPA) and urokinase (UK) are crucial serine proteases involved in fibrinolysis.
• Accurate quantification of active TPA and UK is essential for therapeutic applications and research.
• Existing methods may lack sensitivity or specificity for determining active concentrations.

Purpose of the Study:

• To develop a sensitive and accurate method for determining the molar concentration of active tissue plasminogen activator (TPA) and urokinase (UK).
• To enable the calculation of specific activity for commercial TPA and UK samples.
• To facilitate the determination of kinetic constants for plasma activator inhibitors.

Main Methods:

• Development of a back-titration assay using a calibrated trypsin standard and a chloromethyl ketone inhibitor.
• Calibration of trypsin and inhibitor standards employing a guanidinobenzoyl ester active-site titrant.
• Application of the method for assaying commercial TPA and UK samples.

Main Results:

• The developed method accurately determines the molar concentration of active TPA and UK.
• Quantification of less than 20 ng of activator is achievable with high accuracy.
• The assay is suitable for calculating specific activity and determining inhibitor kinetic constants.

Conclusions:

• A novel and sensitive back-titration method has been established for active TPA and UK quantification.
• This assay provides a reliable tool for biochemical and pharmacological studies involving fibrinolytic enzymes.
• The method supports precise characterization of TPA and UK preparations and their interactions with inhibitors.