One-chain urokinase-type plasminogen activator from human sarcoma cells is a proenzyme with little or no intrinsic activity.
We have compared the plasminogen activating capacity of one- and two-chain urokinase-type plasminogen activator (u-PA). In a 125I-plasminogen conversion assay in the presence of high amounts of a plasmin inhibitor, one-chain u-PA pretreated with diisopropyl fluorophosphate had no detectable activity, the detection limit corresponding to the activity of a 400-fold lower amount of two-chain u-PA. In coupled assays in which generated plasmin was measured with a synthetic substrate, activity was clearly observed with the one-chain preparation, but the initial rate of plasminogen activation was lower than that of a 250-fold smaller concentration of two-chain u-PA. The coupled assays for one-chain u-PA are self-activating because plasmin catalyzes conversion of one- to two-chain u-PA, and it is not possible to decide whether the low activity of one-chain u-PA observed with this type of assay is intrinsic or due to contaminations. On the basis of these findings and a discussion of previous studies, it is concluded that one-chain u-PA has a variety of properties similar to the one-chain proenzyme forms of other serine proteases and that it should, therefore, be considered as a genuine proenzyme form of u-PA.
Petersen
L C
LC
Novo Research Institute, Bagsvoerd, Denmark.
Lund
L R
LR
Nielsen
L S
LS
Danø
K
K
Skriver
L
L
D000465:Algorithms; D004792:Enzyme Precursors / Q000378:metabolism*; D005341:Fibrinolysin / Q000378:metabolism; D006801:Humans; D007531:Isoflurophate / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D010958:Plasminogen / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012509:Sarcoma / Q000201:enzymology*; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*
D004792:Enzyme Precursors; D010446:Peptide Fragments; D011994:Recombinant Proteins; C018998:lysyl-plasminogen; D007531:Isoflurophate; D010958:Plasminogen; D005341:Fibrinolysin; D014568:Urokinase-Type Plasminogen Activator