Fluorogenic polyglutamine-containing peptides with five and ten glutamine residues in a row, having a FRET pair of EDANS (fluorophore) and Dabcyl (quencher), are characterized using spectral and mass spectrometric methods. The possibility of their hydrolysis by the 20S proteasome is examined. The kinetic parameters (catalytic efficiency) for these substances are determined. The presence of glycine in the substrate significantly decreases the solubility of the substrate and diminishes the efficiency of hydrolysis with the proteasome.