Transcriptome Mining of Active Biosynthetic Pathways and Their Associated Products in Streptomyces flaveolus

Diversity of Polyketide Chains Achieved by Deleting the Tailoring Genes in the Biosynthesis of Ansatrienins

The ast gene cluster (GenBank accession numbers KF813023.1 and KP284551) was characterized to be responsible for the biosynthesis of ansatrienins in Streptomyces sp. XZQH13, which contains astC, astF1, and astF2 genes involved in the assembly of the N-cyclohexanoyl d-alanyl side chain and the hydroxylation of C-19, respectively. Further to investigating the biosynthetic mechanism of ansatrienins, herein we constructed the mutant strains XZQH13OEΔastF2 and XZQH13OEΔastCΔastF2. Three new ansatrienin analogues, namely, ansatrienols I-K (1-3), along with trienomycinol (4) and 3-O-demethyltrienomycinol (5), were isolated from the XZQH13OEΔastCΔastF2 strain, and trienomycin A (6) and trienomycin G (7) were isolated from the XZQH13OEΔastF2 strain. Their structures were determined by a combination of high-resolution MS (ESI) and 1D and 2D NMR spectroscopy. Accordingly, a pathway for the biosynthesis of these new ansatrienins was proposed.

Biosynthesis of hygrocins, antitumor naphthoquinone ansamycins produced by Streptomyces sp. LZ35

Hygrocins are naphthoquinone ansamycins with significant antitumor activities. Here, we report the identification and characterization of the hygrocin biosynthetic gene cluster (hgc) in Streptomyces sp. LZ35. A biosynthetic pathway is proposed based on bioinformatics analysis of the hgc genes and intermediates accumulated in selected gene disruption mutants. One of the steps during the biosynthesis of hygrocins is a Baeyer–Villiger oxidation between C5 and C6, catalyzed by luciferase- like monooxygenase homologue Hgc3. Hgc3 represents the founding member of a previously uncharacterized family of enzymes acting as Baeyer–Villiger monooxygenases.