Part of the bacABCDEFG operon responsible for the biosynthesis of bacilysin, an irreversible inactivator of the glutaminase domain of glucosamine synthetase. Catalyzes the formation of alpha-dipeptides from various L-amino acids in the presence of ATP. In vivo catalyzes the ligation of L-alanine and L-anticapsin (epoxycyclohexanonyl-Ala) to produce the final bacilysin antibiotic (L-Ala-L-4S-cyclohexenonyl-Ala dipeptide). ATP + L-alanine + L-anticapsin = ADP + bacilysin + H(+) + phosphate Binds 2 Mg(2+) ions per monomer. Antibiotic biosynthesis; bacilysin biosynthesis. Monomer or homodimer.