Ready-to-use colorimetric substrate for caspases that recognize the amino acid sequence AEVD. Caspase activity can be quantified by spectrophotometric detection of free pNA (l = 400 nm) after cleaved from the peptide substrate AEVD-pNA, using a spectrophotometer or multi-well plate reader. The ready-to-use caspase substrate provides an economical alternative for researchers who perform large volume of caspase assays.