uanteng Ma2, Dehai LiYi Zou1234567890():,;Cytochalasans (CYTs), at the same time as their polycyclic (pcCYTs) and polymerized (meCYTs) derivatives, constitute among the list of largest households of fungal polyketide-nonribosomal peptide (PK-NRP) hybrid natural goods. Nevertheless, the mechanism of chemical conversion from mono-CYTs (moCYTs) to both pcCYTs and meCYTs remains unknown. Here, we show the initial effective example in the reconstitution on the CYT core backbone also as the entire pathway within a heterologous host. Importantly, we also describe the berberine bridge enzyme (BBE)-like oxidase AspoA, which uses Glu538 as a common 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 benefits present an unprecedented function of BBE-like enzymes and hugely recommend that the isolated pcCYTs and meCYTs are probably artificially derived products.1 College of Pharmaceutical Sciences, Southwest University, Chongqing 400715, China. two Crucial Laboratory of Marine Drugs, Chinese Ministry of Education, College of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, China. 3These authors contributed equally: Jin-Mei Zhang, Xuan Liu. email: [email protected] COMMUNICATIONS | (2022)13:225 | doi.org/10.1038/s41467-021-27931-z | nature/naturecommunicationsARTICLENATURE COMMUNICATIONS | doi.org/10.1038/s41467-021-27931-zytochalasans (CYTs), one of several biggest households (400 isolated compounds) of fungal polyketide-nonribosomal peptide (PK-NRP) hybrid organic solutions, exhibit a wide array of essential pharmaceutical and agricultural activities1. They include the frequent feature of an isoindole core fused to an 11 14-membered macrocyclic framework (Fig. 1). The structural complexity of CYTs is mostly attributed to 4 D2 Receptor Inhibitor medchemexpress variable bioconversion processes:2 (1) initial methods mediated by polyketidenonribosomal peptide synthases (PKS-NRPSs) for core backbone synthesis, which can incorporate diverse forms of amino acids (aromatic or aliphatic amino acids) and introduce different modified polyketide chains (Fig. 1a); (2) tailoring measures that happen to be catalysed by a lot of LTC4 Antagonist Molecular Weight distinctive oxidases to type highly oxidised functional groups (Fig. 1b); (3) intermolecular polymerization actions that happen to be performed in undefined approaches, which include the mixture of mono-cytochalasans (moCYTs) with other chemical moieties, through Michael addition, Diels-Alder reaction or heterocycloaddition reactions to form the dimerized or trimerized sorts of mero-cytochalasans (meCYTs, Fig. 1c); and (four) intramolecular C-C or C-O bond linkages which can convert the typical macrocycle framework to the polycyclic skeleton (pcCYTs, Fig. 1d), for example the 5/6/6/5/6-fused pentacyclic ring in aspergillin PZ (1) and its dehydroxylated derivate 2. As a result, these great transformation reactions towards moCYT scaffolds represent a great understanding instance to understand the chemical logic of nature throughout the construction of complex organic products3, and much more importantly, to provide an insightful biomimetic technique for chemists to synthesize this family of compounds42. Since the identification of CYT biosynthetic gene clusters (BGCs) from a variety of fungal species, the biosynthetic pathways along with the functions of their corresponding enzymes happen to be well investigated by numerous groups over the past two decades3,133. Numerous signifi