The lysis time of euglobulin clots made with whole blood (plasma and red cells) was very much shorter than that of clots made with plasma alone, indicating a fibrinolytic component in red cells. A plasminogen activator was found in the stroma-free hemolysate, and proteolytic activity was found in the stromal fraction. The plasminogen activator, purified by using diethylaminoethyl-cellulose (DEAE-cellulose) in a batch procedure followed by column chromatography, was called erythrokinase (EK). On preliminary characterization, EK appears to activate human and bovine plasminogen in a manner similar to urokinase (UK), as determined by fibrinolytic and caseinolytic assays. The two enzymes can be separated by DEAE chromatography and acrylamide-gel electrophoresis, however, and they hydrolyze acetyl-L-lysine methyl ester and benzoyl arginine methyl ester at different rates.
M. Semar, L. Skoza, A. J. Johnson