A new proteinase 3 substrate with improved selectivity over human neutrophil elastase

Area of Science:

• Biochemistry
• Enzymology
• Chemical Biology

Background:

• Proteinase 3 (PR3) is a key serine protease implicated in various inflammatory diseases.
• Existing substrates often lack the required specificity and sensitivity for accurate PR3 detection.
• Neutrophil elastase (NE) shares structural similarities, posing challenges in selective PR3 inhibition and detection.

Purpose of the Study:

• To synthesize and characterize a novel, highly selective intermolecular quenched substrate for proteinase 3 (PR3).
• To evaluate the substrate's specificity and sensitivity for PR3 detection in biological samples.
• To demonstrate the utility of the substrate in detecting PR3 activity in neutrophil lysates.

Main Methods:

• Combinatorial chemistry and mix-and-split methods were employed to synthesize a hexapeptide library.
• Iterative deconvolution was used to identify the optimal peptide sequence.
• Enzymatic assays were performed to determine specificity constants (kcat/KM) and selectivity against related proteases.
• Fluorescence-based detection was utilized to quantify PR3 activity in neutrophil lysates.

Main Results:

• A novel hexapeptide substrate, ABZ-Tyr-Tyr-Abu-Asn-Glu-Pro-Tyr(3-NO2)-NH2, was synthesized.
• The substrate exhibited a high specificity constant (kcat/KM = 1534 × 10^3 M^-1s^-1) for PR3.
• Superior selectivity was demonstrated over neutrophil elastase and other neutrophil-derived serine proteases.
• The substrate enabled the detection of picomolar concentrations of PR3.
• A strong fluorescent signal was observed with neutrophil lysate, significantly reduced by a PR3-selective inhibitor.

Conclusions:

• The developed quenched substrate offers enhanced specificity and sensitivity for proteinase 3.
• This novel tool facilitates accurate detection and quantification of PR3 activity.
• The substrate holds potential for diagnostic applications and research in PR3-related pathologies.