Tetanus toxin acts by inhibiting neurotransmitter release. It binds to peripheral neuronal synapses, is internalized and moves by retrograde transport up the axon into the spinal cord where it can move between postsynaptic and presynaptic neurons. It inhibits neurotransmitter release by acting as a zinc endopeptidase that catalyzes the hydrolysis of the 76-Gln-|-Phe-77 bond of synaptobrevin-2. The precursor polypeptide is subsequently cleaved to yield subchains L and H. These remain linked by a disulfide bridge and are non-toxic after separation.