Measuring net protease activities in biological samples using selective peptidic inhibitors

Area of Science:

• Biochemistry
• Proteomics
• Enzymology

Background:

• Measuring individual protease activity in biological samples is challenging due to enzyme multiplicity, overlapping functions, and substrate specificity issues.
• Existing methods often fail to isolate and quantify the activity of specific proteases within complex biological matrices.

Purpose of the Study:

• To develop and validate a method for the selective quantification of individual protease activities in biological samples.
• To demonstrate the utility of bicyclic peptide inhibitors for accurately measuring protease contributions in mixtures and biological extracts.

Main Methods:

• Application of highly selective bicyclic peptide inhibitors (>2000-fold selectivity) to block specific proteases.
• Utilizing phage display technology for the generation of custom bicyclic peptide inhibitors against target proteases.
• Quantification of net protease activities in protease mixtures and tumor extracts.

Main Results:

• Accurate quantification of serine proteases, including plasma kallikrein and urokinase-type plasminogen activator (uPA), in protease mixtures was achieved.
• The method successfully quantified uPA activity within a complex tumor extract.
• The developed bicyclic peptide inhibitors demonstrated high selectivity, enabling precise activity measurements.

Conclusions:

• The use of selective bicyclic peptide inhibitors provides a robust approach for quantifying individual protease activities in complex biological systems.
• This method overcomes limitations of traditional techniques, offering precise measurement of protease contributions.
• The phage display-based generation of inhibitors makes this approach broadly applicable to virtually any protease of interest.