Synthesis of acridone derivatives via heterologous expression of a plant type III polyketide synthase in Escherichia coli

Bong-Gyu Kim,Joong-Hoon Ahn,Hye Jeong Choo,Gyu-Sik Choi

doi:10.1186/s12934-020-01331-2

Bong-Gyu Kim, Joong-Hoon Ahn + Show 2 more

Open Access

https://doi.org/10.1186/s12934-020-01331-2

Copy DOI

Abstract

BackgroundAcridone alkaloids are heterocyclic compounds that exhibit a broad-range of pharmaceutical and chemotherapeutic activities, including anticancer, antiviral, anti-inflammatory, antimalarial, and antimicrobial effects. Certain plant species such as Citrus microcarpa, Ruta graveolens, and Toddaliopsis bremekampii synthesize acridone alkaloids from anthranilate and malonyl-CoA.ResultsWe synthesized two acridones in Escherichia coli. Acridone synthase (ACS) and anthraniloyl-CoA ligase genes were transformed into E. coli, and the synthesis of acridone was examined. To increase the levels of endogenous anthranilate, we tested several constructs expressing proteins involved in the shikimate pathway and selected the best construct. To boost the supply of malonyl-CoA, genes coding for acetyl-coenzyme A carboxylase (ACC) from Photorhabdus luminescens were overexpressed in E. coli. For the synthesis of 1,3-dihydroxy-10-methylacridone, we utilized an N-methyltransferase gene (NMT) to supply N-methylanthranilate and a new N-methylanthraniloyl-CoA ligase. After selecting the best combination of genes, approximately 17.3 mg/L of 1,3-dihydroxy-9(10H)-acridone (DHA) and 26.0 mg/L of 1,3-dihydroxy-10-methylacridone (NMA) were synthesized.ConclusionsTwo bioactive acridone derivatives were synthesized by expressing type III plant polyketide synthases and other genes in E. coli, which increased the supplement of substrates. This study showed that is possible to synthesize diverse polyketides in E. coli using plant polyketide synthases.

Highlights

Acridone alkaloids are heterocyclic compounds that exhibit a broad-range of pharmaceutical and chemotherapeutic activities, including anticancer, antiviral, anti-inflammatory, antimalarial, and antimicrobial effects
To optimize the substrate supply for the synthesis of acridone, we prepared several sets of constructs; the first set for the synthesis of anthranilate using genes coding for proteins involved in the shikimate pathway and the second set for the synthesis of malonyl-CoA by overexpressing acetylcoenzyme A carboxylases (ACCs)
A new peak was observed in culture filtrates from E. coli strains harboring RgACS-badA or pC-CmACS-badA when they were supplied with anthranilate (Fig. 2d, e)

Summary

Introduction

Acridone alkaloids are heterocyclic compounds that exhibit a broad-range of pharmaceutical and chemotherapeutic activities, including anticancer, antiviral, anti-inflammatory, antimalarial, and antimicrobial effects. Certain plant species such as Citrus microcarpa, Ruta graveolens, and Toddaliopsis bremekampii synthesize acridone alkaloids from anthranilate and malonyl-CoA. Secondary metabolites such as alkaloids, Acridones are heterocyclic alkaloids that contain a tricyclic ring with nitrogen at the 10th position and a carbonyl group at the 9th position [3]. Various acridone derivatives (glyforine, acronycine, thioacridones, and substituted 9-aminoacridines, etc.) have been reported to exert a wide range of chemotherapeutic effects including anticancer, antimicrobial, antimalarial, antipsoriatic activities [5,6,7,8].

Methods

Results

Discussion

Conclusion