Steffimycin

Early acting cyclases play critical roles in programming the polyketide biosynthesis toward certain, distinguished scaffolds. Starting from acetyl-CoA and malonyl-CoA, a one-pot enzymatic total synthesis of an anthracyclinone scaffold, presteffimycinone, was achieved by mixing polyketide synthase (PKS) and early post-PKS enzymes from the biosynthetic pathways of three different types of type II-PKS driven anticancer antibiotics, namely, the mithramycin (aureolic acid-type), gilvocarcin (rearranged angucycline-type), and steffimycin (anthracycline) pathways.

The Embleya genus is a new member of the Streptomycetaceae family formed by only two species isolated from soil (Embleya scabrispora and Embleya hyalina). Strain NF3 is an endophytic actinobacterium obtained from the medicinal tree Amphipterygium adstringens. By 16S rRNA gene analysis, NF3 strain was identified as Embleya sp., closely related to E. hyalina. In our interest to deep into the NF3 strain features, a bioinformatic study was performed on the Embleya genus based on their genome information to produce secondary metabolites. A comparative analysis of the biosynthetic gene clusters (BGCs) of NF3 with the two released Embleya genomes revealed that NF3 has 49 BGCs, E. scabrispora DSM41855 has 50 BGCs, and E. hyalina NBRC13850 has 46 BGCs. Although bearing similar cluster numbers, the three strains shared only 25% of the BGCs information. NF3 encoded the nybomycin cluster detected in E. hyalina NBRC13850 and lacked the hitachimycin cluster present in E. scabrispora DSM41855. On the contrary, strain NF3 contained a cluster for the anthracycline steffimycin, neither encoded by E. hyalina NBRC13850 nor by E. scabrispora DSM41855. Our results and previous characterization studies supported strain NF3 as a new member of the genus Embleya. The chemical analysis of the steffimycins produced by strain NF3 showed the production of eight compounds of the steffimycins and steffimycinone families. Four of these molecules have already been described: steffimycin B, steffimycin C, 8-demethoxy-10-deoxysteffimycinone, and 7-deoxiesteffimycinone, and four are new natural products: 8-demethoxysteffimycin B, 8-demethoxy-10-deoxysteffimycin B, 7-deoxy-8-demethoxysteffimycinone, and 7-deoxy-10-deoxysteffimycinone. With this information, we proposed an alternative pathway to produce StefB. Among steffimycins, StefB was the main compound produced by this strain (29.8%) and showed the best cytotoxic activity. KEY POINTS: · The Embleya genus and its biosynthetic potential · An alternative biosynthetic pathway for steffimycins biosynthesis · Four new natural products of the steffimycin family.

The marine actinomycete strain OPMA02852, identified as the genus Streptomyces, was found to produce anti-mycobacterial compounds against Mycobacterium avium complex (MAC). One new compound, designated as steffimycin E (1), was isolated together with three known steffimycins (steffimycin (2), 10-dihydrosteffimycin (3), and 8-demethoxysteffimycin (4)) from the culture broth of this producing microorganism by solvent extraction, ODS column chromatography, and preparative HPLC. Compound 1 has a tetracyclic quinone structure with a sugar moiety. Compound 1 exhibited anti-mycobacterial activity against M. intracellulare, M. bovis BCG, and M. smegmatis.