PROTEOLYSIS OF SYNTHETIC PEPTIDES BY TYPE-A BOTULINUM NEUROTOXIN

Type A botulinum neurotoxin catalyzed the hydrolysis of synthetic pept ides based on the sequence of the 25-kD synaptosomal protein SNAP-25. In each peptide, the toxin cleaved at a single glutaminyl-arginine bon d corresponding to residues 197 and 198 of SNAP-25, confirming earlier reports on the enzymatic specificity of the toxin in synaptosomaI pre parations. Metal chelators inhibited catalysis, consistent with a meta lloprotease activity. In contrast to tetanus toxin and other botulinum toxin serotypes, type A toxin hydrolyzed relatively short, 17- to 20- residue peptides. In the substrates, SNAP-25 residue 202 and one or mo re of residues 187-191 were required for efficient hydrolysis, but res idues 167-186 and 203-206 were not. The highest rates of hydrolysis we re found when the C-terminal residues of the peptides were amidated.