Abstract
A single polypeptide chain-high molecular weight urokinase purified from human kidney tissue culture was not decomposed autocatalytically, although it was easely traesformed to lower molecular weight forms (mol. wts. 31, 000-36, 000) by trypsin, plasmin, papain, and especially by elastase treatments. The new enzymes porduced had almost the same pyro-Glu-Gly-Arg-pNA amidolytic activity, but showed lower Glu-plasminogen-activating activity than those of the parent enzyme. Using immunological and fibrin-Sepharose column techniques, it was confirmed that the new enzymes lacked the light chain corresponding part of the urinary HMW-UK molecule and had much lower affinity for the fibrin molecule.
The Lys-plasmin was also found to be very sensitive to papain treatment, and subsequent production of a new enzyme (mol. wt. 45, 000-52, 000) was observed.
The urinary trypsin-plasmin inhibitor, UTI67 could be also fragmented by papain and pronase tratments. Five new inhibitors (mol. wts. 6, 500-26, 000) purified from papain-treated UTI67, exhibited much higher auti-plasmin/antitrypsin activities than those of the parent UTI.
It is possible that such enzymatic modifications of enzyme and inhibitor molecules could play a significant role in vivo in the regulation of plasma and tissue fibrinolytic systems.
