An Internally Quenched Fluorescent Peptide Substrate for Protealysin

Area of Science:

• Biochemistry
• Enzymology
• Microbiology

Background:

• Protealysin is a metalloprotease from Serratia proteamaculans and the prototype of a subgroup within the M4 peptidase family.
• Protealysin-like proteases (PLPs) are prevalent in bacteria, fungi, and archaea, with significant implications for animal and plant pathogenesis.

Purpose of the Study:

• To develop an efficient quantitative assay for measuring the activity of protealysin-like proteases (PLPs).
• To characterize the substrate specificity and kinetic parameters of protealysin and thermolysin using the newly developed assay.

Main Methods:

• A novel internally quenched fluorescent peptide substrate was synthesized based on the autoprocessing site sequence of the protealysin precursor.
• Enzyme kinetics, including Michaelis-Menten constants (K_M) and catalytic rates (k_cat), were determined for protealysin and thermolysin.
• The substrate's specificity was evaluated against a panel of different proteases.

Main Results:

• The developed substrate specifically detects hydrolysis at the Ser-Val bond by both protealysin and thermolysin.
• Protealysin exhibited a K_M of 35 ± 4 μM and k_cat of 21 ± 1 s^-1, while thermolysin showed a K_M of 33 ± 8 μM and k_cat of 7 ± 1 s^-1.
• While not strictly specific, the substrate demonstrated higher molar activity for protealysin compared to other tested enzymes, including thermolysin.

Conclusions:

• The novel fluorescent peptide substrate provides an effective tool for the quantitative assay of protealysin activity.
• This assay is also valuable for studying the activity of other M4 peptidases, aiding research into bacterial pathogenesis and enzyme mechanisms.