A simple procedure is described for the preparation from pregnant hog ovaries of a highly purified tissue plasminogen activator containing 100,000-175,000 tissue activator units/mg of protein. Tissue activator differs from the activator in urine (urokinase). Only within certain limits and under specified conditions is it possible to compare their activities in the same unitage. In fibrin plate assays one tissue activator unit was comparable to 0.1 CTA human urokinase unit. Gel filtration in glycine buffer at pH 2.35 indicated a molecular size of about 60,000 which is larger than the main component observed in urokinase preparations (mol wt 54,000). Though uniform by gel filtration, the tissue activator preparation could be further fractionated by zone electrophoresis. The active component had a mobility close to that of one of the active urokinase components and to that of bovine serum albumin. The properties of the tissue activator make it unlikely that it could be the source of plasminogen activator in urine. © 1969, American Chemical Society. All rights reserved.
