In enzymology, a diphthine—ammonia ligase (, diphthamide synthase, diphthamide synthetase) is an enzyme that catalyzes the chemical reaction
ATP + diphthine + NH3 ADP + phosphate + diphthamide
The 3 substrates of this enzyme are ATP, diphthine, and NH3, whereas its 3 products are ADP, phosphate, and diphthamide.
This enzyme belongs to the family of ligases, specifically those forming carbon-nitrogen bonds as acid-D-amino-acid ligases (peptide synthases). The systematic name of this enzyme class is diphthine:ammonia ligase (ADP-forming). Other names in common use include diphthamide synthase, and diphthamide synthetase.
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