C-1027 is an enediyne antitumor antibiotic composed of an apo-protein (CagA) and a reactive enediyne chromophore containing four distinct chemical moieties including an (S)-3-chloro-5-hydroxy-βtyrosine moiety,the biosynthesis of which from L-α-requires six proteins; SgcC.SgcC1,SgcC2.SgcC3,SgcC4.and SgcCS.SgcC5 is homologous to condensation domains of nonribosomal peptide synthetases,and it has been shown to catalyze ester bond formation between the SgcC2-tethered (S)-3-chloro-5-hydroxy-β-tyrosine and (R)-1-pheny1-1.2-ethanediol.a mimic of the enediyne core.thereby supporting the proposed role of SgcC5 in the incorporation of the β-amino acid moiety into C-1027.