Characterization of the high-affinity interaction between human plasminogen and pro-urokinase.
Activation of human Glu-plasminogen, Lys-plasminogen and low-Mr plasminogen (lacking lysine-binding sites) by pro-urokinase (pro-UK), obtained from a human lung adenocarcinoma cell line (Calu-3, ATCC), obeys Michaelis-Menten kinetics. Activation occurs with a comparable affinity (Km 0.40-0.77 microM), while the catalytic rate constant (kcat) is comparable for Glu-plasminogen (0.0022s-1) and low-Mr plasminogen (0.0034 s-1), but is somewhat higher for Lys-plasminogen (0.0106 s-1). The rate of activation of plasminogen by pro-UK is not significantly influenced by the presence of 6-aminohexanoic acid, purified fragments LBS I or LBS II or histidine-rich glycoprotein, indicating that the high affinity of pro-UK for plasminogen is not mediated via the high-affinity lysine-binding site of plasminogen located in kringles 1-3 (LBS I) nor via the low-affinity lysine-binding site comprised within kringle 4 (LBS II). The site(s) in plasminogen involved in the high-affinity interaction with pro-UK thus appear to be located within the low-Mr plasminogen moiety.
D000230:Adenocarcinoma; D001665:Binding Sites; D002460:Cell Line; D006801:Humans; D007700:Kinetics; D008024:Ligands; D008175:Lung Neoplasms; D008970:Molecular Weight; D010446:Peptide Fragments / Q000378:metabolism; D010958:Plasminogen / Q000378:metabolism*; D010960:Plasminogen Activators / Q000378:metabolism*; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*
D008024:Ligands; D010446:Peptide Fragments; C018998:lysyl-plasminogen; D010958:Plasminogen; D010960:Plasminogen Activators; D014568:Urokinase-Type Plasminogen Activator