The present invention provides a novel modified BoNT/E catalytic domain and methods of use thereof. In one embodiment, the light chain residue 224, or a residue corresponding to residue 224, of the modified BoNT/E catalytic domain has been altered to be aspartic acid or glutamic acid. The modified catalytic domain cleaves SNAP23 but does not cleave SNAP29 or SNAP47, providing novel methods of treating diseases including without limitation, asthma, CF, chronic obstructive pulmonary, gastric acid efflux and inflammation, immune disorders with a cytokine component or cancers with a cytokine component.