Ready-to-use colorimetric substrate for caspase-6/Mch2 and related caspases that recognize the amino acid sequence VEID. Caspase-6 and related caspase activity can be quantified by spectrophotometric detection of free pNA (l= 400 nm) after cleavage from the peptide substrate VEID-pNA, using a spectrophotometer or multi-well plate reader.