string: Although the internally quenched substrate Abz-(R)4SAGnYamide was shown previously to be efficiently cleaved by DEN NS2B(H)-NS3pro, (kcat/Km: 11087 M 21 s(21)) [22], binding affinity and cleavage efficiency (kcat/Km: 19 M 21 s(21)) of this peptide was substantially lower (approx.