FR901469, a novel antifungal antibiotic from an unidentified fungus No. 11243. III. Structure determination

Fungi-derived lipopeptide antibiotics developed since 2000

Lipopeptide antibiotics have linear or cyclic structures with one or more hydrocarbon tails linked to the N-terminus of a short oligopeptide that may be chemically modified and/or contain unusual amino acid residues in their structures. They possess huge potential as pharmaceutical drugs and biocontrol agents, and ˜30 representative genera of fungi are known to produce them. Some chemically synthesised derivatives have already been developed into commercial products or subjected to clinical trials, including cilofungin, caspofungin, micafungin, anidulafungin, rezafungin, emodepside, fusafungine and destruxins. This review summarizes 200 fungi-derived compounds reported since 2000, including 95 cyclic depsipeptides, 67 peptaibiotics (including 35 peptaibols, eight lipoaminopeptides, and five lipopeptaibols), and 38 non-depsipeptide and non-peptaibiotic lipopeptides. Their sources, structural sequences, antibiotic activities (e.g. antibacterial, antifungal, antiviral, antimycobacterial, antimycoplasmal, antimalarial, antileishmanial, insecticidal, antitrypanosomal and nematicidal), structure-activity relationships, mechanisms of action, and specific relevance are discussed. These compounds have attracted considerable interest within the pharmaceutical and agrochemical industries.

Synthesis of new fluorinated proline analogues from polyfluoroalkyl β-ketoacetals and ethyl isocyanoacetate

New straightforward synthetic approach to hitherto unknown cis-/trans-CF₃-prolines and other 3-polyfluoroalkyl proline analogues.

Further enhancement of FR901469 productivity by co-overexpression of cpcA, a cross-pathway control gene, and frbF in fungal sp. No. 11243

FR901469 is a secondary metabolite with antifungal activity, produced by fungal sp. No. 11243. In our previous study, we constructed the frbF overexpression mutant (TFH2-2) from the wild-type strain. FR901469 productivity of TFH2-2 was 3.4 times higher than that of the wild-type strain. To further enhance FR901469 productivity in TFH2-2, we attempted to find genes from the genome that limited the productivity as bottlenecks in this study. Based on both correlation analysis of gene expression level against FR901469 productivity and genome annotation information, the cross-pathway control gene A (cpcA) was most predicted as the bottleneck. The cpcA and frbF co-overexpression mutant named TFCH3 was then constructed from TFH2-2. As a result, FR901469 productivity of TFCH3 was enhanced at 1.8 times higher than that of TFH2-2. Transcriptome analysis revealed that many genes involved in amino acid biosynthesis and encoding tRNA ligases were significantly upregulated in TFCH3, which implied increase of amino acids as the substrates of FR901469 would be a reason of further productivity enhancement.

Identification of a putative FR901469 biosynthesis gene cluster in fungal sp. No. 11243 and enhancement of the productivity by overexpressing the transcription factor gene frbF

FR901469 is an antifungal antibiotic produced by fungal sp. No. 11243. Here, we searched for FR901469 biosynthesis genes in the genome of No. 11243. Based on the molecular structure of FR901469 and endogenous functional motifs predicted in each genomic NRPS gene, a putative FR901469 biosynthesis gene cluster harboring the most plausible NRPS gene was identified. A transcription factor gene, designated frbF, was found in the cluster. To improve FR901469 productivity, we constructed a strain in which frbF was overexpressed and named it TFH2-2. FR901469 productivity of TFH2-2 was 3.4 times higher than that of the wild-type strain. Transcriptome analysis revealed that most of the genes in the putative FR901469 biosynthesis gene cluster were upregulated in TFH2-2. It also showed that the expression of genes related to ergosterol biosynthesis, β-1,3-glucan catabolism, and chitin synthesis was inclined to exhibit significant differences in TFH2-2.

Genome Sequence of Fungal Species No.11243, Which Produces the Antifungal Antibiotic FR901469

Fungal species No.11243 was originally isolated from a decayed leaf sample collected in Kyoto, Japan. It produces FR901469, a 1,3-beta-glucan synthase inhibitor. The genome sequence of No.11243 was determined and annotated to obtain useful information for improving productivity of the effective antifungal agent FR901469.

From natural products to clinically useful antifungals

In our search for natural products with a broad spectrum of antifungal activity as lead compounds for novel treatments for mycoses, we have isolated echinocandin-type lipopeptide FR901379 and lipopeptidolactone FR901469, as novel water-soluble antifungal agents that inhibit the synthesis of 1,3-beta-glucan, a key component of the fungal cell wall. Since the cell wall is a feature unique to fungi and is not present in nonfungal eukaryotic cells, inhibitors of the synthesis of fungal cell wall components such as 1,3-beta-glucan have potential for selective toxicity to fungi and not to the host. In this short review, we describe efforts directed at synthetic modification of FR901469 and FR901379 with the ultimate goal of identifying new entities with suitable profiles as development candidate compounds. The main thrust of our work to date has been replacement of the highly flexible lipophilic side chains of the natural products with a view to reducing the hemolytic potential associated with these compounds, and to enhance chemical stability and/or in vivo antifungal efficacy. As a result of these efforts, we recently discovered a novel analog, FK463 (micafungin). Micafungin is currently in phase III clinical trials worldwide as a parenteral agent for various mycoses, and a new drug application (NDA) was recently filed in Japan.