Zymogen-activation kinetics. Modulatory effects of trans-4-(aminomethyl)cyclohexane-1-carboxylic acid and poly-D-lysine on plasminogen activation.
The kinetics of plasminogen activation catalysed by urokinase and tissue-type plasminogen activator were investigated. Kinetic measurements are performed by means of a specific chromogenic peptide substrate for plasmin, D-valyl-L-leucyl-L-lysine 4-nitroanilide. Two methods are proposed for the analysis of the resulting progress curve of nitroaniline formation in terms of zymogen-activation kinetics: a graphical transformation of the parabolic curve and transformation of the curve for nitroaniline production into a linear progress curve by the addition of a specific inhibitor of plasmin, bovine pancreatic trypsin inhibitor. The two methods give similar results, suggesting that the reaction between activator and plasminogen is a simple second-order reaction at least at plasminogen concentrations up to about 10 microM. The kinetics of both Glu1-plasminogen (residues 1-790) and Lys77-plasminogen (residues 77-790) activation were investigated. The results confirm previous observations showing that trans-4-(aminomethyl)cyclohexane-1-carboxylic acid at relatively low concentrations enhances the activation rate of Glu1-plasminogen but not that of Lys77-plasminogen. At higher concentrations both Glu1- and Lys77-plasminogen activation are inhibited. The concentration interval for the inhibition of urokinase-catalysed reactions is shown to be very different from that of the tissue-plasminogen activator system. Evidence is presented indicating that binding to the active site of urokinase (KD = 2.0 mM) is responsible for the inhibition of the urokinase system, binding to the active site of tissue-plasminogen activator is approx. 100-fold weaker, and inhibition of the tissue-plasminogen activator system, when monitored by plasmin activity, is mainly due to plasmin inhibition. Poly-D-lysine (Mr 160 000) causes a marked enhancement of plasminogen activation catalysed by tissue-plasminogen activator but not by urokinase. Bell-shaped curves of enhancement as a function of the logarithm of poly-D-lysine concentration are obtained for both Glu1- and Lys77-plasminogen activation, with a maximal effect at about 10 mg/litre. The enhancement of Glu1-plasminogen activation exerted by trans-4-(aminomethyl)cyclohexane-1-carboxylic acid is additive to that of poly-D-lysine, whereas poly-D-lysine-induced enhancement of Lys77-plasminogen activation is abolished by trans-4-(aminomethyl)cyclohexane-1-carboxylic acid. Analogies are drawn up between the effector functions of poly-D-lysine and fibrin on the catalytic activity of tissue-plasminogen activator.
Petersen
L C
LC
Brender
J
J
Suenson
E
E
D007611:Aprotinin / Q000494:pharmacology; D003509:Cyclohexanecarboxylic Acids / Q000494:pharmacology*; D004789:Enzyme Activation; D005341:Fibrinolysin / Q000378:metabolism; D007700:Kinetics; D010455:Peptides / Q000494:pharmacology*; D010958:Plasminogen / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011107:Polylysine / Q000494:pharmacology*; D014148:Tranexamic Acid / Q000494:pharmacology*; D014568:Urokinase-Type Plasminogen Activator / Q000494:pharmacology
D003509:Cyclohexanecarboxylic Acids; D010455:Peptides; C020858:cis-4-aminomethylcyclohexane-1-carboxylic acid; D011107:Polylysine; D014148:Tranexamic Acid; D010958:Plasminogen; D007611:Aprotinin; D005341:Fibrinolysin; D014568:Urokinase-Type Plasminogen Activator