[1S05a] 13. Microbial Engineering for Natural Products Synthesis - Part 2

2:45 PM - 3:00 PM JST(5:45 AM - 6:00 AM UTC)

[1MENP-08] Stepwise Ring Expansion as a Biosynthetic Strategy for Macrocycle Construction

○Hayama Tsutsumi^1,2, Reona Suzuki², Akihiro Ishii², Ayano Komaki³, Mariko Takanashi², Yuka Yamakawa³, Yoshihiro Watanabe^1,2, Tomohiro Suzuki², Masato Iwatsuki^1,2, Tomoyasu Hirose^1,2, Hidehito Matsui^1,2, Toshiaki Sunazuka^1,2, Akihiro Sugawara^1,2, Yuki Inahashi^1,2 (1. Ōmura Satoshi Memorial Institute, Kitasato University (Japan), 2. Graduate School of Infection Control Sciences, Kitasato University (Japan), 3. Graduate School of Science, Kitasato University (Japan))

Keywords:

naturalproduct,biosynthesis,polyketide,macrocycle,ring expansion

Luminamicin (1) is a macrodiolide antibiotic featuring a unique 5/14/10/6/6/6 hexacyclic ring system, an oxa-bridged cis-decaline, and a rare alkenyl ether moiety. Despite its structural complexity, the biosynthetic mechanisms underlying this intricate scaffold remain elusive. Here, we identified the biosynthetic gene cluster for 1 in Streptomyces sp. OMR-59 and elucidated its biosynthetic pathway through gene disruption, metabolic analysis, and in vitro characterization of recombinant enzymes, revealing an unprecedented enzymatic cascade governing its biosynthesis. Polyketide synthases and some modification enzymes catalyze the formation a 10/6/6 tricyclic polyketide intermediate. A key acyl transfer reaction then introduces (Z)-hex-3-ene-1,3,4-tricarboxylic acid anhydride at an unexpected position. Subsequent tailoring reactions further modify this intermediate, constructing a key intermediate with both 10/6/6/6 and 10/5 ring systems. This intermediate is then converted into a compound with a 5/13/10/6/6/6 hexacyclic scaffold through hydroxylation and an internal acyl transfer reaction. Finally, an unexpected oxidative rearrangement expands the 13-membered ring into a 14-membered system, establishing the 5/14/10/6/6/6 hexacyclic core with an alkenyl ether moiety. This study uncovers a previously uncharacterized biosynthetic transformation, reveals novel enzymatic strategies for macrodiolide assembly, and enhances our understanding of complex polycyclic architectures.