Protease Detection

A method of detection of a protease enzyme in a sample, comprising the steps of:

• (i) exposing the sample to a polypeptide comprising a chromogenic amino acid, wherein the chromogenic amino acid is flanked by at least one amino acid to the N and C termini thereof, the amine group of the chromogenic amino acid has a pKa of less than 5 and the chromogenic amino acid is capable of reacting with a conjugated aldehyde, and wherein the polypeptide comprises a target sequence for a target protease which is capable of cleaving the peptide bond comprising the amino group of the chromogenic amino acid;
• and allowing the protease to cleave the polypeptide and create a fragment displaying the chromogenic amino acid to the N-terminus of the fragment;
• (ii) reacting a conjugated aldehyde with the fragment comprising the chromogenic amino acid to produce a colored adduct;
• and
• (iii) detecting the colored adduct, the presence of the colored adduct being indicative of the presence of the protease enzyme in the sample.