Exoenzyme

Exoenzymes (Exo) are secreted by cells and break large macromolecules outside the cells. The breakdown components can pass through the cell wall. Exo C3 is a Clostridium butulinum toxin which binds NAD, splits it into ADP-ribose and nicotinamide and transfers the ADP-ribose to a protein substrate. Exo S and Exo T are secreted by Pseudomonas aeruginosa and has GTPase-activating activity as well as ADP-ribosyltransferase activity^[1] .

in exoenzyme C3 catalytic domain (PDB code 2c8c).