GMP synthase (EC 188.8.131.52, xanthosine-5'-phosphate—ammonia ligase, guanylate synthetase, XMP aminase, xanthosine 5'-monophosphate aminase) is an enzyme with system name xanthosine-5'-phosphate:ammonia ligase (AMP-forming). This enzyme catalyses the following chemical reaction
- ATP + XMP + NH3 <math>\rightleftharpoons</math> AMP + diphosphate + GMP
- ^ Moyed, H.S. and Magasanik, B. (1957). "Enzymes essential for the biosynthesis of nucleic acid guanine; xanthosine 5′-phosphate aminase of Aerobacter aerogenes". J. Biol. Chem. 226: 351–363. PMID 13428768.