Abstract
Fungal maleidrides are an important family of bioactive secondary metabolites that consist of 7, 8, or 9‐membered carbocycles with one or two fused maleic anhydride moieties. The biosynthesis of byssochlamic acid (a nonadride) and agnestadride A (a heptadride) was investigated through gene disruption and heterologous expression experiments. The results reveal that the precursors for cyclization are formed by an iterative highly reducing fungal polyketide synthase supported by a hydrolase, together with two citrate‐processing enzymes. The enigmatic ring formation is catalyzed by two proteins with homology to ketosteroid isomerases, and assisted by two proteins with homology to phosphatidylethanolamine‐binding proteins.
Highlights
Analytical grade chemicals and reagents were supplied from Sigma-Aldrich, Alfa Aesar, Acros Organics, BectonDickinson, BDH, Fischer, Fluka and Difco, unless otherwise stated
A. oryzae NSAR1 was obtained as a gift from the Kitamoto group.[2]
A. oryzae NSAR1 was maintained on MEA, liquid induction medium was 100 ml CMP in 500 ml flasks (3.5% w/v Czapek Dox Broth, 2% w/v D-(+)-maltose monohydrate, 1% w/v peptone) at 28 °C with shaking at 200 rpm for 7 days
Summary
Analytical grade chemicals and reagents were supplied from Sigma-Aldrich, Alfa Aesar, Acros Organics, BectonDickinson, BDH, Fischer, Fluka and Difco, unless otherwise stated. Solvents used for LC-DAD-MS analyses were HPLC grade. General molecular biology procedures were performed as standard[1] and molecular biology kits used according to manufacturer’s protocols. Analytical PCR was performed using BioMix Red (Bioline) and preparative PCR was performed using Phusion polymerase (NEB)
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