This amidase catalyses the last step in the conversion of an?L-histidine residue in the translation elongation factor translation elongation factor 2 to diphthamide. This factor is found in all archaebacteria and eukaryotes, but not in eubacteria, and is the target of bacterial toxins such as the diphtheria toxin and the?Pseudomonas?exotoxin A (see EC?2.4.2.36, NAD+¡ªdiphthamide ADP-ribosyltransferase). The substrate of the enzyme, diphthine, is produced by EC?2.1.1.98, diphthine synthase.
