There is major interest in designing inhibitors for matrix metalloproteinase 2 (MMP-2, gelatinase A) since this enzyme is known to be involved in pathological processes such as tumor invasion or rheumatoid arthritis. The majority of MMP-2 inhibitor candidate drugs block the active site of MMP-2 by binding to its catalytic Zn2+ ion through a chelating (hydroxamate, sulphonate etc.) group. Despite the general interest in designing MMP-2 inhibitors, the results with many of the drug candidates were disappointing, their failure was usually explained by cross-reactions with other MMPs. One way to enhance MMP-2 selectivity is to design inhibitors that interact with both the active site and exosites such as the fibronectin type II (FN2) domains of the enzyme. In the present work, we have examined the inhibitory potential and MMP-2 selectivity of hydroxamates of three groups of peptides known to bind to the collagen-binding FN2 domains of MMP-2. The first type of peptides consisted of collagen-like (Pro-Pro-Gly)(n) repeats, peptides of the second group were identified from a random 15-mer phage display library based on their binding to immobilized FN2 domains of MMP-2. A hydroxamate of peptide p33-42, known to bind to the third FN2 domain of MMP-2 has also been tested. Our studies have shown that these compounds inhibited MMP-2 with IC50 values of 10-100 microM. The fact that their inhibitory potential was nearly identical for MMP-2del, a recombinant version of MMP-2 that lacks the FN2 domains, suggests that inhibition is not mediated by their binding to FN2 domains. It seems likely that the failure to exploit interaction with the FN2 domains is due to the fact that the FN2 domains and the catalytic domain of MMP-2 tumble independently, therefore only a tiny fraction of the conformational isomers can bind peptide hydroxamates via both the active site and the FN2 domain(s).