Metallopeptidase inhibitors of tetanus toxin: A combinatorial approach

The bacterial protein tetanus toxin (TeNt), which belongs to the family of zinc endopeptidases, cleaves synaptobrevin, an essential synaptic protein c omponent of the neurotransmitter exocytosis apparatus, at a single peptide bond (Gln(76)-Phe(77)). This protease activity is a particularly attractive target for designing potent and selective synthetic inhibitors as a possib le drug therapy for tetanus. beta-Aminothiols mimicking Gln(76) of synaptob revin have been previously shown to inhibit the tetanus neurotoxin enzymati c activity in the 35-250 mu M range. These compounds have now been modified to interact with S' subsites of the TeNt active site, with the aim of incr easing their inhibitory potencies. Combinatorial libraries of pseudotripept ides, containing an ethylene sulfonamide or an m-sulfonamidophenyl moiety a s the P-1 side chain and natural amino acids in P-1' and P-2' positions, we re synthesized. The best inhibitory activity was observed with Tyr and His as P-1' and P-2' components, respectively. This led to new inhibitors of Te Nt with K-i values in the 3-4 mu M range. These molecules are the most pote nt inhibitors of TeNt described so far.