Berberine bridge enzyme-like oxidase-catalysed double bond isomerization acts as the pathway switch in cytochalasin synthesis

Abstract

Cytochalasans (CYTs), as well as their polycyclic (pcCYTs) and polymerized (meCYTs) derivatives, constitute one of the largest families of fungal polyketide-nonribosomal peptide (PK-NRP) hybrid natural products. However, the mechanism of chemical conversion from mono-CYTs (moCYTs) to both pcCYTs and meCYTs remains unknown. Here, we show the first successful example of the reconstitution of the CYT core backbone as well as the whole pathway in a heterologous host. Importantly, we also describe the berberine bridge enzyme (BBE)-like oxidase AspoA, which uses Glu538 as a general acid biocatalyst to catalyse an unusual protonation-driven double bond isomerization reaction and acts as a switch to alter the native (for moCYTs) and nonenzymatic (for pcCYTs and meCYTs) pathways to synthesize aspochalasin family compounds. Our results present an unprecedented function of BBE-like enzymes and highly suggest that the isolated pcCYTs and meCYTs are most likely artificially derived products.

Deciphering chemical logic of fungal natural product biosynthesis through heterologous expression and genome mining

“…180 The pioneering discoveries of CghA and Fsa2 have led to the identication of other lipocalin-like pericyclases including Eqx3, PvhB, 181 MycB, 125 UcsH, 164 and AspoB. 182 Depending on molecular orbitals (MO) involved in the reaction, DA reaction can be further classied as normal- Natural Product Reports Review electron demand Diels-Alder reactions (NEDDA) and inverseelectron demand Diels-Alder reactions (IEDDA). In the case of NEDDA, the DA reaction happens between an electron-rich dienophile and an electron-decient diene, while in IEDAA, the reaction takes place between an electron-rich diene and an electron-poor dienophile.…”

“…180 The pioneering discoveries of CghA and Fsa2 have led to the identification of other lipocalin-like pericyclases including Eqx3, PvhB, 181 MycB, 125 UcsH, 164 and AspoB. 182…”

Hetero-Diels-Alder Reaction Coupled with Semipinacol Rearrangement for the Biosynthesis of Structurally Diversified Notoamides

“…S7). 2,30,31 Tetrahydrocannabinolic acid (THCA) synthase, belonging to this family, could catalyze the oxidative cyclization of the monoterpene moiety in cannabigerolic acid (CBGA). 32 Therefore, we hypothesized that SpeE might be involved in the construction of the 2H-pyran ring in notoamides.…”

Recent advances in the total synthesis of cytochalasan natural products using bioinspired strategies

“…The biosynthesis routes and the functions of their associated enzymes have been thoroughly explored by numerous groups since the identification of cytochalasanbiosynthetic gene clusters from distinct fungal species over the past 20 years. 7 However, the biosynthetic pathways of pentacyclic cytochalasans and merocytochalasans remain unknown. The bioinspired synthesis of pentacyclic cytochalasans and merocytochalasans validated the proposed biosynthetic speculation from a chemical viewpoint and paved the way for the synthesis and structure elucidation of other types of cytochalasans bearing different macrocycles and amino acid residues.…”