Human plasmin enzymatic activity is inhibited by chemically modified dextrans

Some synthetic dextran derivatives that mimic the action of heparin/heparan sulfate were shown to promote in vivo tissue repair when added alone to wo unds. These biofunctional mimetics were therefore designated as "regenerati ng agents" in regard to their in vivo properties. In vitro, these biopolyme rs were able to protect various heparin-binding growth factors against prot eolytic degradation as well as to inhibit the enzymatic activity of neutrop hil elastase. In the present work, different dextran derivatives were teste d for their capacity to inhibit the enzymatic activity of human plasmin. We show that dextran containing carboxymethyl, sulfate as well as benzylamide groups (RG1192 compound), was the most efficient inhibitor of plasmin amid olytic activity. The inhibition of plasmin by RG1192 can be classified as t ight binding hyperbolic noncompetitive. One molecule of RG1192 bound 20 mol ecules of plasmin with a K-i of 2.8 x 10(-8) M. Analysis with an optical bi osensor confirmed the high affinity of RG1192 for plasmin and revealed that this polymer equally binds plasminogen with a similar affinity (K-d = 3 x 10(-8) M), Competitive experiments carried out with 6-aminohexanoic acid an d kringle proteolytic fragments identified the lysine-binding site domains of plasmin as the RG1192 binding sites. In addition, RG1192 blocked the gen eration of plasmin from Glu-plasminogen and inhibited the plasmin-mediated proteolysis of fibronectin and laminin, Data from the present in vitro inve stigation thus indicated that specific dextran derivatives can contribute t o the regulation of plasmin activity by impeding the plasmin generation, as a result of their binding to plasminogen and also by directly affecting th e catalytic activity of the enzyme.