<P> In vivo , chymotrypsin is a proteolytic enzyme ( Serine protease ) acting in the digestive systems of many organisms . It facilitates the cleavage of peptide bonds by a hydrolysis reaction , which despite being thermodynamically favorable occurs extremely slowly in the absence of a catalyst . The main substrates of chymotrypsin are peptide bonds in which the amino acid N - terminal to the bond is a tryptophan , tyrosine , phenylalanine , or leucine . Like many proteases , chymotrypsin will also hydrolyse amide bonds in vitro , a virtue that enabled the use of substrate analogs such as N - acetyl - L - phenylalanine p - nitrophenyl amide for enzyme assays . </P>
where does cleavage of the peptide bond by chymotrypsin occur
digestive systems