Comparison of Certain Properties of Human Plasminogen and “Proactivator”

Summary Human plasma and highly purified soluble human plasminogen contain the same proactivator: plasminogen ratio. The difference in apparent stability of plasminogen and proactivator was traced to the difference in solubility as effected by the pH of the respective assays. During the autocatalytic conversion of plasminogen to plasmin, proactivator content diminishes as plasmin is formed. A discussion of these observations is presented, wherein it is proposed that human plasminogen and the proactivator of bovine plasminogen in human plasminogen are the same factor.