Medium effects on the kinetics of human plasmin

Abstract

Effects of water-miscible organic solvents added to an aqueous buffer on the activity of several serine proteinases were studied. Plasmin in particular showed a dramatic difference in activity depending on the hydrophobicity of the added organic solvent through a combination of Km and kcat effects. An inverse linear correlation between the polarity of the mixed solvent and the log (kcat/Km) of plasmin activity was observed for both H-D-Val-Leu-Lys-p-nitroanilide (S-2251) and pro-urokinase as the substrate. The activity of plasmin was less dependent on the polarity of the added solvent when other chromogenic substrates were employed that contained an arginyl residue in the P1 site.