Kinetic measurements of either Ac-VEID-AFC or lamin A cleavage by fluorescence or our newly developed ELISA allowed comparison of the kinetic parameters of caspase-6 for the two substrates. We find that the full-length lamin A protein has a more than 1000fold lower Km than its cleavage site peptide VEID (Table 1) . Although the kcat value is also decreased, the kcat/Km is still more than 10fold higher for lamin A (Table 1 ). This indicates that the binding between lamin A and caspase-6 is tighter, which might be mediated by domains outside the cleavage site. Such binding sites could also be responsible for the observed specificity of caspase-6 for the full-length protein substrate. The Km and kcat values for VEID are furthermore in good agreement with previously reported data [4] .