antibiotic biosynthesis aminocoumarin biosynthesis novobiocin biosynthesis pathway PMID:16868863 Biosynthesis of novobiocin. The novobiocin molecule comprises three structural moieties: the deoxy sugar noviose, a substituted 3-aminocoumarin moiety and a 3-prenylated 4-hydroxybenzoate moiety. Noviose is related to L-rhamnose, but shows an unusual 5,5-dimethyl structure and carries a carbamyl group at 3-OH and a methyl group at 4-OH. The aminocoumarin ring is substituted with hydroxy groups in positions 3 and 7. Novobiocin and coumermycin A1 carry a methyl group at position 8 of the aminocoumarin unit, while clorobiocin (also called chlorobiocin) is chlorinated in this position. In clorobiocin and coumermycin A1, the 3-OH of the deoxy sugar is connected with a 5-methylpyrrole-2-carboxyl moiety rather than with a carbamyl group. While clorobiocin contains the same prenylated 4-hydroxybenzoate moiety as novobiocin, the coumermycin A1 molecule contains a central 3-methylpyrrole-2,4-dicarboxylic acid moiety, which links two aminocoumarin-deoxy sugar assemblies in a nearly but not completely symmetrical fashion. PMID:10770754 UPa:UPA01035