Antithrombin effects of native and recombinant hirudins.

Three recombinant variants of hirudin with the most evident difference in amino acid position 47 (Lys-47, Arg-47, Asn-47) were studied for their selectivity and affinity for the target enzyme thrombin in comparison to native hirudin. Native hirudin and the recombinant hirudins inhibit selectively the clotting enzyme thrombin. The affinity of native hirudin does not differ significantly from that of recombinant hirudin Lys-47 whereas a distinctly lower affinity for thrombin is found for recombinant hirudin Arg-47 and recombinant hirudin Asn-47. All hirudins investigated have the same potency to inhibit thrombin-induced coagulation. Changes in the affinity of hirudins for thrombin become evident from the inhibition of thrombin-induced platelet aggregation only.