N-(p-Tosyl)-GPR-pNA is a colorimetric substrate for thrombin. Thrombin preferentially binds to and cleaves the Gly-Pro-Arg (GPR) peptide sequence to release p-nitroanilide (pNA), which can be quantified by colorimetric detection at 405 nm as a measure of thrombin activity.
N-(p-Tosyl)-GPR-pNA acetate (Chromozym-TH) is a chromogenic substrate targeting the synthetic peptides Hirunorm IV and Hirunorm V and can be used to detect the dissociation constants (KI) of both peptides. Hirunorm IV and Hirunorm V are reversible inhibitors of amidolytic thrombin activity. By varying the peptide concentration at a fixed concentration of the chromogenic substrate N-(p-Tosyl)-GPR-pNA acetate, the dissociation constants determined were 0.134 nM (Hirunorm IV) and 0.245 nM (Hirunorm V)[1].
