We previously described that collagen-coated synthetic polymer composite was adequately applicable as a support of immobilization of enzymes, and that urokinase-bearing composite showed good fibrinolytic activity. Now the immobilized urokinase was characterized enzymatically as compared with the native enzyme. Apparent affinity for the substrate was slightly decreased, but intrinsic kinetic properties were not significantly affected. No decrease in esterase activity was observed both on repeated use and on long-term storage, and fibrinolytic activity was stable on heat and disinfection. When applied to rabbit blood vessel, the in vivo retainment of the activity depended largely on adsorption of plasma protein and blood cells.
