The present invention concerns a method to detect the presence of an
enzyme in
in vivo or
in vitro tissue or
cell, which method comprises:(a) obtaining a tissue or
cell sample to be analyzed;(b) contacting the tissue or
cell sample with a substrate of the structure selected from the group consisting of:X=H or one or more natural or synthetic amino acids with or without amino blocking groups,Y=H or one or more natural or synthetic amino acids with or without amino blocking groups,wherein X and Y are the same or different and are
amino acid sequences of between about 1 to 1,000,000 amino acids wherein each
amino acid is the same or a different
amino acid, with the proviso that at least one of X or Y is at least one amino acid;(c) when an
enzyme is present in the tissue or cell sample which degrades X, Y and combinations thereof, fluorescent cresyl violet is released in the
tissue sample producing a color change;(d) detecting the presence and amount of the
enzyme present by the detection and quantification of the
fluorescence produced; and(e) optionally comparing the
fluorescence to a pre-calibrated
fluorescence scale to quantify the fluorescence present. A diagnostic kit for use and a method to prepare amino acid cresyl violet derivatives are described.