A Unique Pathway for the 3-Aminobutyrate Starter Unit from L-Glutamate through β-Glutamate during Biosynthesis of the 24-Membered Macrolactam Antibiotic, Incednine

Incednine is a 24-membered macrolactam antibiotic produced by Streptomyces sp. ML694-90F3. A previous study demonstrated that its unique nitrogen-containing starter unit was derived from L-glutamate. To elucidate the missing link between L-glutamate and the starter unit, deuterium labeled amino acid feeding experiments were conducted. These experiments revealed that 3[3-H-2]aminobutyrate end beta-[2,2,4,4-H-2(4)]glutamate were incorporated into the starter moiety. The results indicate that a novel decarboxylation of beta-glutamate to give 3-aminobutyrate is involved in incednine biosynthesis.