Wei_2026_Mar.Drugs_24_103

Nenestatins (NENs) belong to benzo[b]fluorene-containing atypical angucyclines, a structurally diverse class of microbial natural products. Bioinformatic analysis of the NEN biosynthetic gene cluster (nes BGC) from the deep-sea sediment-derived Micromonospora echinospora SCSIO 04089 implicated Nes5 as an alpha/beta hydrolase. The targeted inactivation of the nes5 gene led to the accumulation of five new analogs, NENs E-I (1-5), together with the known monomer homo-dehydrorabelomycin E (6). Their structures were elucidated by comprehensive spectroscopic analysis and electronic circular dichroism calculations. Notably, both NEN A and NEN B were absent in the deltanes5 mutant, indicating that Nes5 is essential for their biosynthesis; however, the exact function of Nes5 requires further exploration.