The heterologous expression of the lobophorin biosynthetic gene cluster from marine-derived Streptomyces pactum SCSIO 02999 has led to the discovery of new analogues that carry d-kijanose (or its variants with a 3-amino or hydroxyl group) at C-9. The identification of intermediates resulting from the inactivation of lobG1 (encoding C-17 kijanosyltransferase) and lobG3 (encoding C-9 digitoxosyltransferase) demonstrates the substrate flexibility of LobG3 to also accept d-kijanose and its variants. Notably, two lobophorins with d-kijanose at C-9 show improved bioactivities.

A new uridine derivative 11457A (1), and a new indole derivative 11457B (2), together with a known compound 1H-indole-2-carbaldehyde (3), were characterized from the fermentation broth of the actinomycete Pseudonocardia sp. SCSIO 11457, an isolate associated with the scleractinian coral Galaxea fascicularis. Upon detailed spectroscopic analysis, 11457A (1) was identified as uridine analog, and 11457B (2) was elucidated as an indole derivative 2-hydroxy-1-(1H-indol-2-yl)pentane-1,4-dione.Biological evaluation indicated that none of compounds 1-3 showed antibacterial activities against pathogenic bacteria and cytotoxic activities against human cancer cell lines.

Functions of the tailoring enzymes for the biosynthesis of tiacumicin B (1) have been previously determined. However, the reaction timing remains elusive. Herein, we report the in vitro biochemical characterization of two P450 enzymes TiaP1 and TiaP2. The investigation of their substrate scope and kinetic parameters clearly demonstrates that the TiaP2-catalyzed C-20 hydroxylation is the first tailoring step and the TiaP1-catalyzed C-18 hydroxylation is the last step in the biosynthesis of 1.

The unprecedented eight-membered heterocyclic chrysonin (1) was isolated from an Antarctic fungus that also produced xanthocillins 4 and 5 as potent inhibitors against Gram-negative pathogens.