Involved in the biosynthesis of the antimetabolite L-2-amino-4-methoxy-trans-3-butenoic acid (AMB), a non-proteinogenic amino acid which is toxic for prokaryotes and eukaryotes (PubMed:20543073, PubMed:25814981). Adenylates L-glutamate and loads it onto its first peptidyl carrier domain via a thioester linkage to the phosphopanthetheine moiety (PubMed:25814981). The second peptidyl carrier domain is loaded with a L-alanine activated by AmbB (PubMed:25814981). After formation by AmbB of the L-Glu-L-Ala dipeptide at the first carrier domain of AmbE, the condensation domain of AmbE probably condenses this dipeptide with the L-Ala residue attached at the second carrier domain of AmbE to give the L-Ala-L-Glu-L-Ala tripeptide. The central amino acid, L-Glu, would then undergo a series of modifications to be converted into AMB while the two flanking L-Ala residues remain in place (PubMed:25814981). Finally, the L-Ala-AMB-L-Ala tripeptide is probably released by thioester cleavage via the thioester domain of AmbE (PubMed:25814981). ATP + holo-[peptidyl-carrier protein] + L-glutamate = AMP + diphosphate + L-glutamyl-[peptidyl-carrier protein] Expression is regulated by the PhoR-PhoB two-component system. Modular protein that contains an adenylation domain which activates the glutamate residue into an aminoacyl-AMP ester, a methyltransferase domain, a first peptidyl carrier protein domain which bears a phosphopantetheinyl arm to attach the activated L-glutamate, a condensation domain involved in the condensation of this amino acid with a second amino acid bound at the carrier protein domain of another module, a second peptidyl carrier protein domain which bears a phosphopantetheinyl arm to attach a L-alanine activated by AmbB and a thioesterase domain that may release the newly synthesized peptide from the enzyme. Mutation abolishes AMB production (PubMed:20543073). Deletion of the gene causes a substantial reduction in the production of the quorum sensing signal 2-heptyl-3-hydroxy-4(1H)-quinolone (PQS) (PubMed:23542643). Belongs to the NRP synthetase family. It was suggested by Lee et al that the amb cluster is involved in the biosynthesis of 2-(2-hydroxyphenyl)-thiazole-4-carbaldehyde (IQS), a cell-cell communication signal that modulates the production of AMB through the pqs and rhl quorum sensing systems (PubMed:23542643). The chemical structure of IQS indicates that this compound may be assembled from salicylate and cysteine. However, neither of the two peptide synthases encoded by the amb gene cluster present adenylation domains with a specificity for these substrates. It is thus highly implausible that IQS is specified by the amb gene cluster (PubMed:25814981).