The Biosynthesis of Norsesquiterpene Aculenes Requires Three Cytochrome P450 Enzymes to Catalyze a Stepwise Demethylation Process

Abstract

Aculenes are a unique class of norsequiterpenes (C14) that are produced by Aspergillus aculeatus. The nordaucane skeleton in aculenes A–D may be derived from an ent‐daucane precursor through demethylation, however, the enzymes involved remain unexplored. We identified the biosynthetic gene cluster and characterized the biosynthetic pathway based on gene inactivation, feeding experiments, and heterologous reconstitution in Saccharomyces cerevisiae and Aspergillus oryzae. We discovered that three cytochrome P450 monoxygenases are required to catalyze the stepwise demethylation process. AneF converts the 12‐methyl group into a carboxylic acid and AneD installs the 10‐hydroxy group for later tautomerization and stabilization. Finally, AneG installs an electron‐withdrawing carbonyl group at the C‐2 position, which triggers C‐12 decarboxylation to yield the nordaucane skeleton. Additionally, a terpene cyclase (AneC) was found that forms a new product (dauca‐4,7‐diene).

Fungal Metabolite Asperaculane B Inhibits Malaria Infection and Transmission

“…The active compound was isolated and determined to be asperaculane B. The structure of asperaculane B has resolved previously [12,14]. Notably, asperaculane B also inhibited asexual P. falciparum infection in blood while being nontoxic to human cells.…”

“…Therefore, we hypothesize that C1 is asperaculane B. Instead of repeating previously published work [12,14,15], we obtained a set of pure compounds (Figure 6b), including the pure asperaculane B ( Figure S1) from two laboratories, where the compounds were isolated from A. aculeatus in 2015 [12] and 2019 [14]. We determined the malaria transmission-blocking activity of these compounds with SMFA at 10 µg/mL and fed An.…”

Aphananoid A is an Anti-Inflammatory Limonoid with a New 5/6/5 Fused Ring Featuring a C24 Carbon Skeleton from Aphanamixis polystachya

“…Finally, the C-7 ester group was hydrolyzed, and decarboxylation happened through carbon dioxide removal. 21 Aphananoid A was evaluated for its anti-inflammatory activity and inhibition of NO production in the RAW264.7 cell line, showing 46.80 ± 1.93% and approximately 51.31 ± 1.17% for the positive control (L-NMMA) at 50 μM (Figure 6). Therefore, we next determined the IC 50 value (Figure 6) of anti-inflammatory activity, and the bioassay showed an IC 50 value of 66.73 μM and a lower value for the control L-NMMA (46.96 μM).…”

“…Triterpenes have been considered to be the origin of all tetranortriterpenoids. After multiple oxidations and C-30 methyl transfers, the basic limonoid skeleton was formed, and the A/B ring simultaneously ruptured via oxidations, which led to intermediate 1 . , After checking the related literature, − we deduced that decarbonization was divided into two steps, and ring B was formed by comparatively rational aldol condensation. The C-8–C-30 olefin was oxidized to form a C-8 ketone .…”

Biosynthesis of Terpenoid–Pyrrolobenzoxazine Hybrid Natural Product CJ‐12662

“…fumagillin, Figure 1B) [16] . The convergence of amino acids and terpene scaffolds is however rare, with two recent examples in aculene A [17] and flavunoidine [18] . The clear chemical benefit of combining terpene and amino acid biosynthesis is enrichment of compounds with nitrogen atoms, which are rare among hydrocarbon‐derived terpenoids [19] .…”