N-(3-(2-furyl) acryloyl)-L-phenylalanyl-glycyl-glycine (FAPGG) have the maximum absorption peak at 340 nm. ACE1 catalyzes hydrolysis of FAPGG substrate to furanyl phenylalanine (FAP) and glycylglycine (GG), and the absorbance at 340 nm will be decreased. The activity of ACE1 can be calculated indirectly by measuring the decrease in absorbance at 340 nm.
