Reaction: ATP + diphthine + NH3 = ADP + phosphate + diphthamide
Other name(s): diphthamide synthase; diphthamide synthetase
Systematic name: diphthine:ammonia ligase (ADP-forming)
Comments: This amidase catalyses the last step in the conversion of an L-histidine residue in the translation elongation factor eEF-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+—diphthamide ADP-ribosyltransferase). The substrate of the enzyme, diphthine, is produced by EC 2.1.1.98, diphthine synthase. The nature of the ammonia donor is not known.
Links to other databases: BRENDA, EXPASY, KEGG, CAS registry number:
References:
1. Moehring, J.M. and Moehring, T.J. The post-translational trimethylation of diphthamide studied in vitro. J. Biol. Chem. 263 (1988) 3840-3844. [PMID: 3346227]
2. Moehring, T.J. and Moehring, J.M. Mutant cultured cells used to study the synthesis of diphthamide. UCLA Symp. Mol. Cell. Biol. New Ser. 45 (1987) 53-63.