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A steadily increasing number of reports have been published on chemo-enzymatic synthesis methods that integrate biosynthetic enzymatic transformations with chemical conversions. This review focuses on the total synthesis of natural products and classifies the enzymatic reactions into three categories. The total synthesis of five natural products: cotylenol, trichodimerol, chalcomoracin, tylactone, and saframycin A, as well as their analogs, is outlined with an emphasis on comparing these chemo-enzymatic syntheses with the corresponding natural biosynthetic pathways., (Copyright © 2024, Tanifuji and Oguri.)

Thioredoxin (Trx) is a disulfide-containing redox protein that functions as a disulfide oxidoreductase. Myxococcus xanthus contains five Trxs (Trx1-Trx5) and one Trx reductase (TrxR). Trxs typically have a CGPC active-site motif; however, M. xanthus Trxs have slightly different active-site sequences, with the exception of Trx4. The five Trxs of M. xanthus exhibited reduced activities against insulin, 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), cystine, glutathione disulfide (GSSG), S-nitrosoglutathione (GSNO), and H2O2 in the presence of TrxR. Myxococcus xanthus adenylate kinase and serine/threonine phosphatase activities, which were increased by the addition of dithiothreitol, were activated by the addition of Trxs and TrxR. Among these, Trx1, which has a CAPC sequence in its active site, exhibited the highest reducing activity with the exception of GSNO. Myxococcus xanthus TrxR showed weak reducing activity towards DTNB, GSSG, GSNO, and H2O2, suggesting that it has broad substrate specificity, unlike previously reported low-molecular-weight TrxRs. TrxR reduced oxidized Trx1 as the best substrate, with a kcat/Km value of 0.253 min-1 µM-1, which was 10-28-fold higher than that of the other Trxs. These results suggest that all Trxs possess reducing activity and that Trx1 may be the most functional in M. xanthus because TrxR most efficiently reduces oxidized Trx1., (© The Author(s) 2024. Published by Oxford University Press on behalf of FEMS.)

Covering: 2000 to 2019Rapid access to genomic data has facilitated the identification of the biosynthetic enzyme genes of alkaloid natural products and elucidation of their biosynthetic pathways. Enzymes for the rapid construction of molecular scaffolds and versatile modifications during the late-stage biosynthesis of complex molecular skeletons constitute unique features of biosynthetic machineries. For example, enzymes involved in an alkaloid biosynthesis. In this review, we discuss three types of useful enzymes and enzymatic reactions that have been found in the biosynthetic studies of several alkaloids, and discuss their applications for the total synthesis of natural alkaloids and their derivatives. The selected examples include a single non-ribosomal peptide synthetase SfmC that catalyzes key Pictet-Spengler reactions, which construct a characteristic tetrahydroisoquinoline skeleton in antitumor antibiotics such as saframycin, prenylation-oxidative modification enzymes involved in the biosynthesis of fungal tremorgenic mycotoxins such as penitrem as well as versatile Diels-Alderases recently discovered in the biosynthesis of plant monoterpene indole alkaloids of iboga and aspidosperma type.

C5-desoxy analogs of tetrahydroisoquinoline (THIQ) alkaloids were designed and synthesized as hitherto unexplored structural variants for evaluation of their DNA alkylating activities. While chemical synthesis of the C5-desoxy analogs bearing a phenolic hydroxyl group in the A-ring of the saframycins was assumed to be laborious based on semi-synthetic modifications, a chemo-enzymatic approach allowed for concise access to the analogs. The C5-desoxy analog 7 exhibited greater DNA alkylating ability with a wider tolerance for the sequence variations compared to cyanosafracin B. The C5-desoxy A-ring having a C8 phenolic hydroxyl group, and a C1 substituent in the vicinity of the C21 aminonitrile responsible for DNA alkylation, were demonstrated to play pivotal roles in the interaction between the THIQ alkaloids and DNA., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The antitumor tetrahydroisoquinoline (THIQ) alkaloids share a common pentacyclic scaffold that is biosynthesized by nonribosomal peptide synthetases involving unique enzymatic Pictet-Spengler cyclizations. Herein we report concise and divergent chemo-enzymatic total syntheses of THIQ alkaloids by merging precise chemical synthesis with in vitro engineered biosynthesis. A recombinant enzyme SfmC responsible for the biosynthesis of saframycin A was adapted for the assembly of these natural products and their derivatives, by optimizing designer substrates compatible with SfmC through chemical synthesis. The appropriately functionalized pentacyclic skeleton were efficiently synthesized by streamlining the linkage between SfmC-catalyzed multistep enzymatic conversions and chemical manipulations of the intermediates to install aminonitrile and N-methyl groups. This approach allowed rapid access to the elaborated pentacyclic skeleton in a single day starting from two simple synthetic substrates without isolation of the intermediates. Further functional group manipulations allowed operationally simple and expeditious syntheses of jorunnamycin A, saframycin A, and N-Fmoc saframycin Y3 that could be versatile and common precursors for the artificial production of other antitumor THIQ alkaloids and their variants.