N-ethoxycarbonyl-D-phenylalanyl-L-prolyl-α-azalysine p-nitrophenyl ester: A novel, high selective and optimal chromogenic active site titrant for human and bovine α-, β- and γ-thrombin

The serine proteinase catalyzed hydrolysis of N-ethoxycarbonyl-D-phenylalanyl-L-prolyl-α-azalysine p-nitrophenyl ester (Eoc-D-Phe-Pro-azaLys-ONp) was investigated at pH 6.2 and 21.0°C. The results are consistent with the minimum three-step catalytic mechanism. The acylation step is rate limiting for human (Lys77 species) and porcine plasmin, and for bovine β-trypsin, the deacylation rate being limiting, on the other hand, for human and bovine α-, β- and γ-thrombin. Moreover, the M(r) 33,000 species of human urokinase and the neuraminidase-treated porcine pancreatic β-kallikrein-B do not catalyze the hydrolysis of the tripeptide. According to the specificity properties of the serine proteinases considered, Eoc-D-Phe-Pro-azaLys-ONp shows the characteristics of a novel, high selective and optimal chromogenic active site titrant for human and bovine α-, β- and γ-thrombin.