Studies on a Proteolytic Enzyme System of the Blood. IV. Activation of Profibrinolysin by Serum Fibrinolysokinase.

Abstract

Serum profibrinolysin (plasminogen) activates "spontaneously" to fibrinolysin under certain conditions, e.g., CHCI3 treatment and protein fractionation by certain methods. This "spontaneous" activation of CHCI3 serum is shown to be independent of cellular elements originally present in the mother plasma. Two serum fractions, euglobulin and prolysin, prepared from the same serum showed high profibrinolysin content (capable of activation with staphylokinase) and no antifibrinolysin. Fibrinolysin appeared in the euglobulin fraction but not in the prolysin fraction. This was thought to be due to the presence in the euglobulin fraction of a fibrinolysokinase. Such a fibrinolysokinase was isolated from serum and shown to activate profibrinolysin.