Production of the Bengamide Class of Marine Natural Products in Myxobacteria: Biosynthesis and Structure–Activity Relationships

Abstract

The bengamides, sponge‐derived natural products that have been characterized as inhibitors of methionine aminopeptidases (MetAPs), have been intensively investigated as anticancer compounds. We embarked on a multidisciplinary project to supply bengamides by fermentation of the terrestrial myxobacterium M. virescens, decipher their biosynthesis, and optimize their properties as drug leads. The characterization of the biosynthetic pathway revealed that bacterial resistance to bengamides is conferred by Leu 154 of the myxobacterial MetAP protein, and enabled transfer of the entire gene cluster into the more suitable production host M. xanthus DK1622. A combination of semisynthesis of microbially derived bengamides and total synthesis resulted in an optimized derivative that combined high cellular potency in the nanomolar range with high metabolic stability, which translated to an improved half‐life in mice and antitumor efficacy in a melanoma mouse model.

The Bengamides: A Mini-Review of Natural Sources, Analogues, Biological Properties, Biosynthetic Origins, and Future Prospects

“…In 2015, the Muller–Bronstrup team published the definitive results that were described in Figure 4 of the paper. 38 Molecular genetics experiments resulted in isolation of the bengamide gene cluster (a 731 kDa protein of about 25 kbp and nine genes: coded BenA to BenG) from cultures of the Gram-negative bacterium Myxococcus virescens . This organism produces four bengamides (E/E′, F/F′) and was isolated initially in 2005 from a terrestrial soil sample by scientists at Sanofi Adventis, 39 and subsequently a sample of this strain was obtained and cultured at UCSC.…”

“…The success of three different groups in obtaining useable yields of bengamides from laboratory culturing of Gram-negative microorganisms is an important development. 38−40 It also sets the stage for future investigations of the microbiome of Jaspis cf. coriacea .…”

“…1e,3,38,42−48 Compounds with single-digit nanomolar or subnanomolar activity against MDA-MB-435 or HCT-116 tumor cell lines represent important inputs for the design of a potential clinical candidate. Alternatively, minor modifications of the polyketide OCH 3 group, changing the absolute configurations at positions C-5 to C-8, or replacing the caprolactam with unoptimized subunits can be disastrous.…”

“…After the discovery that the bengamides are also produced by the terrestrial myxobacterium Myxococcus virescens ST200611 (DSM 15898), 38−40 a campaign to supply bengamides by fermentation was launched, resulting in elucidation of the responsible biosynthetic gene cluster. 38 Further analysis of the biosynthetic pathway showed that Leu154 of the myxobacterial MetAP confers bacterial self-resistance to bengamide inhibition via steric hindrance. The entire gene cluster was then successfully transferred to a robust strain of M. xanthus DK1622 for large-scale fermentation.…”

“…38,40 The recent characterization from Myxococcus virescens of the bengamide gene cluster provides powerful insights about how this process proceeds and could be further manipulated. 38 The first biosynthetic step involves (see Figure 11) loading of a 2-methylbutyrl-CoA starter unit, which is subsequently modified by a BenA–D assembly of the key glycolate unit and further transformed by BenE–H. This latter cassette installs the functionality and chirality at bengamide positions C-5 to C-8 required for nanomolar bioactivity (see Figures 7 and 8).…”