Target Accumulation of Selective Anticancer Depsipeptides by Reconstructing Precursor Supply in Neoantimycins Biosynthetic Pathway

Abstract BackgroundNeoantimycins are a group of 15-membered ring depsipeptides isolated from streptomycetes with a broad-spectrum of anticancer activities. Their biosynthesis is directed by the hybrid multimodular megaenzymes of non-ribosomal peptide synthetase and polyketide synthase. We have previously discovered a new neoantimycin analogue unantimycin B, which was demonstrated with selective anticancer activities and was produced from neoantimycins biosynthetic pathway with a starter unit of 3-hydroxybenzoate, instead of the 3-formamidosalicylate for neoantimycins. However, the low fermentation yield and tough isolation procedure have been hindering in-depth pharmacology investigation of unantimycin B as anticancer agents.ResultsIn the work, we genetically constructed two unantimycin B producer strains with neoantimycins production destroyed by removing natO and natJ-L genes essential for 3-formamidosalicylate biosynthesis and therefore facilitated chromatographic separation of unantimycin B from the complex fermentation extract. Based on the △natO mutant, we improved unantimycin Bproduction by two times, reaching to approximate 12.8 mg/L, by feeding 3-hydroxybenzoate in fermentation. Further, the production was improved by more than six times, reaching to approximate 40.0 mg/L, in the △natO strain introduced with a chorismatase gene highly expressed under a strong promoter for over-producing 3-hydroxybenzoate endogenously.ConclusionThe work gives a case of targeting accumulation and significant production improvement of medicinally interesting natural products via genetically manipulation of precursor biosynthesis in streptomycetes, the talented producers of pharmaceutical molecules.