Part of the bacABCDEF operon responsible for the biosynthesis of the nonribosomally synthesized dipeptide antibiotic bacilysin, composed of L-alanine and L-anticapsin. Bacilysin is an irreversible inactivator of the glutaminase domain of glucosamine synthetase (PubMed:15609023, PubMed:20052993). BacB catalyzes the allylic isomerization of the endocyclic-delta(4),delta(8)-7R-dihydro-hydroxyphenylpyruvate (en-H2HPP) to generate a mixture of 3E,7R- and 3Z, 7R-olefins (E/Z ration of 3/1) of the exocyclic-delta(3),delta(5)-dihydro-hydroxyphenylpyruvate (ex-H2HPP) (PubMed:20052993, PubMed:22483065, PubMed:22765234, PubMed:19776011). 3-[(4R)-4-hydroxycyclohexa-1,5-dien-1-yl]-2-oxopropanoate = 3-[(1E,4R)-4-hydroxycyclohex-2-en-1-ylidene]pyruvate Binds 2 Fe(2+) or Co(2+) ions per subunit. kcat is 1471 min(-1) for isomerase activity with en-H2HPP as substrate. Antibiotic biosynthesis; bacilysin biosynthesis. Monomer. The compound guanosine 5'-diphosphate 3'-diphosphate (ppGpp) is essential for the transcription of the bacABCDEF operon and BacG, and GTP regulates the transcription of both this operon and ywfH via the CodY-mediated regulation system.