Summary
Human chromosomal DNA encoding single-chain urokinase-type Plasminogen Activator (scu-PA,
or pro-urokinase) was inserted in an expression plasmid and transfected in human A431,
mouse LB6 and CHO cells. LB6 cells were also transfected with a Bovine Papilloma Virus
derivative containing the scu-PA gene. Human scu-PA was purified from cell supernatants
of recombinant clones and characterized for structure and function.
All recombinant scu-PAs are undistinguishable from human urine-derived scu-PA for
peptide backbone, but possess a higher sugar content, as revealed by SDS-PAGE analysis
after digestion with glycopeptidase F. This difference is partly due to an increased
sialic acid content, as shown by analysis of neuraminidase-treated scu-PAs.
No difference was found, however, among recombinant and natural scu-PAs in the kinetics
of conversion into two-chain active forms (tcu-PAs) by human plasmin, and in the KM and kcat values of tcu-PA activity on the chromogenic substrate S-2444 and on human plasminogen.
Also, recombinant and non-recombinant tcu-PAs displayed similar dose-response curves
for binding to the endothelial inhibitor PAI-1.
In conclusion, the glycosylation pattern of u-PA does not affect its interaction with
the plasma proteins directly involved in its fibrinolytic function.
Keywords
Single-chain urokinase-type Plasminogen Activator - Prourokinase - Recombinant DNA
- Glycosylation - Plasminogen Activator Inhibitor type-1