GP-pNA, Chromogenic Substrate is a chromogenic substrate for CD26 (dipeptidyl peptidase IV, DPIV, DPPIV), DPP7/II, DPRP1 (DPP8), DPRP2 (DPP9), FAP, Angiotensinase C (PCP/PRCP), PREP/POP, and likely other prolyl peptidases. GP-pNA, Chromogenic Substrate has been employed in vitro for inhibitor screening, on cultured cells, and in biological fluids. Hydrolysis of GP-pNA, Chromogenic Substrate can be monitored at 405-410 nm.