STUDIES ON A PROTEOLYTIC ENZYME SYSTEM OF THE BLOOD. II. FIBRINOLYSOKINASE ACTIVATORS FOR PROFIBRINOLYSIN 1

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Abstract
Dog tissues were fractionated by differential centrifugation. "Microsome" and "large granule" fractions of various tissues, in particular lung and uterus, were found to contain fibrinolysokinase activity for dog serum profibrinolysin. Similar fractions prepared from lung tissue of mouse, rat, guinea pig, cat, dog and human were able to activate dog, human and bovine pro-fibrinolysins at least partially. Rabbit lung fractions showed poor and bovine lung no kinase activity. Activation of profibrinolysin was rapid but incomplete at 37[degree]C, much slower but produced higher yields of fibrinolysin at 4[degree]C. Apparently staphylokinase and dog lung fibrinolysokinase act on the same profibrinolysin, the yield of fibrinolysin being maximal with staphylokinase but incomplete with the present prepns. of lung kinase. The dog lung fraction was highly thromboplastic but surprisingly also highly antithrombic. The thromboplastic and fibrinolysokinase activities could be separated by heat lability and heparin inhibition.
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