title: Steady-state kinetics of plasmin- and trypsin-catalysed hydrolysis of a number of tripeptide-p-nitroanilides.
abstract: The steady-state kinetics of plasmin- (EC 3.4.21.7) and trypsin-catalysed (EC 3.4.21.4) hydrolysis of Bz-L-Phe-Val-Arg-pNA, Bz-D-Phe-Val-Arg-pNA, L-Phe-Val-Arg-pNA, D-Phe-Val-Arg-pNA and D-Val-Leu-Lys-pNA were investigated in the pH range 6-9. The pH dependences of the kinetic parameters correspond with the effects of catalytically essential ionizations in the enzymes, except for reactions with L- and D-Phe-Val-Arg-pNA, in which protonation of the NH2-terminal alpha-amino groups (pK = 7.0) shows some inhibitory effect. The reactions of plasmin and trypsin with p-nitroanilides show kc values similar to those normally found with specific ester substrates, indicating that the deacylation steps of the reactions are rate determining.
mesh_terms: D000813:Anilides / Q000378:metabolism; D005341:Fibrinolysin / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009842:Oligopeptides / Q000378:metabolism*; D014357:Trypsin / Q000378:metabolism*
chemical_list: D000813:Anilides; D009842:Oligopeptides; D014357:Trypsin; D005341:Fibrinolysin