In enzymology, a UDP-N-acetylmuramoyl-L-alanine—D-glutamate ligase (EC 6.3.2.9) is an enzyme that catalyzes the chemical reaction

ATP + UDP-N-acetylmuramoyl-L-alanine + D-glutamate ADP + phosphate + UDP-N-acetylmuramoyl-L-alanyl-D-glutamate

The 3 substrates of this enzyme are ATP, UDP-N-acetylmuramoyl-L-alanine, and D-glutamate, whereas its 3 products are ADP, phosphate, and UDP-N-acetylmuramoyl-L-alanyl-D-glutamate.

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 UDP-N-acetylmuramoyl-L-alanine:D-glutamate ligase (ADP-forming). Other names in common use include MurD synthetase, UDP-N-acetylmuramoyl-L-alanyl-D-glutamate synthetase, uridine diphospho-N-acetylmuramoylalanyl-D-glutamate synthetase, D-glutamate-adding enzyme, D-glutamate ligase, UDP-Mur-NAC-L-Ala:D-Glu ligase, UDP-N-acetylmuramoyl-L-alanine:glutamate ligase (ADP-forming), and UDP-N-acetylmuramoylalanine-D-glutamate ligase. This enzyme participates in d-glutamine and d-glutamate metabolism and peptidoglycan biosynthesis.

As of late 2007, 9 structures have been solved for this class of enzymes, with PDB accession codes 1E0D, 1EEH, 1UAG, 2JFF, 2JFG, 2JFH, 2UAG, 3UAG, and 4UAG.

• Muramyl ligase

• Ito, E; Strominger JL (1962). "Enzymatic synthesis of the peptide in bacterial uridine nucleotides I. Enzymatic addition of L-alanine, D-glutamic acid, and L-lysine". J. Biol. Chem. 237: 2689–2695. doi:10.1016/S0021-9258(19)73808-3.
• van Heijenoort J (October 2001). "Recent advances in the formation of the bacterial peptidoglycan monomer unit". Natural Product Reports. 18 (5): 503–19. doi:10.1039/a804532a. PMID 11699883.