Identification of a diarylpentanoid-producing polyketide synthase revealing an unusual biosynthetic pathway of 2-(2-phenylethyl)chromones in agarwood

Xiao-Hui Wang,Peng-Fei Tu,Jun Li,Ikuro Abe,Yuan-E Lee,Qian-Qian Liu,Juan Wang,Hiroyuki Morita,Zhong-Xiu Zhang,Bo-Wen Qi,Chin-Piow Wong,Bo-Wen Gao,Ze-Kun Zhang,Yu Nakashima,She-Po Shi,Xiao Liu,Takeshi Kodama,Takahiro Mori

doi:10.1038/s41467-022-27971-z

Abstract

2-(2-Phenylethyl)chromones (PECs) are the principal constituents contributing to the distinctive fragrance of agarwood. How PECs are biosynthesized is currently unknown. In this work, we describe a diarylpentanoid-producing polyketide synthase (PECPS) identified from Aquilaria sinensis. Through biotransformation experiments using fluorine-labeled substrate, transient expression of PECPS in Nicotiana benthamiana, and knockdown of PECPS expression in A. sinensis calli, we demonstrate that the C6–C5–C6 scaffold of diarylpentanoid is the common precursor of PECs, and PECPS plays a crucial role in PECs biosynthesis. Crystal structure (1.98 Å) analyses and site-directed mutagenesis reveal that, due to its small active site cavity (247 Å3), PECPS employs a one-pot formation mechanism including a “diketide-CoA intermediate-released” step for the formation of the C6–C5–C6 scaffold. The identification of PECPS, the pivotal enzyme of PECs biosynthesis, provides insight into not only the feasibility of overproduction of pharmaceutically important PECs using metabolic engineering approaches, but also further exploration of how agarwood is formed.

Highlights

2-(2-Phenylethyl)chromones (PECs) are the principal constituents contributing to the distinctive fragrance of agarwood
It has been demonstrated that the formation of agarwood is characteristically accompanied by the synthesis and accumulation of sesquiterpenoids and 2-(2-phenylethyl)chromones (PECs), which are the principal constituents contributing to the important biological activities and the pleasant fragrance of agarwood[14,15,16,17]
We demonstrated that PECs in agarwood are biosynthesized from a common precursor featuring a C6–C5–C6 skeleton produced by a diarylpentanoid-producing polyketide synthase, hereafter named 2-(2-phenylethyl)chromone precursor synthase (PECPS)

Summary

Introduction

2-(2-Phenylethyl)chromones (PECs) are the principal constituents contributing to the distinctive fragrance of agarwood. Crystal structure analyses suggested that PECPS utilizes unique catalytic machinery with the formation and release of a diketide-CoA intermediate to form the C6–C5–C6 scaffold, which has not been previously reported in other known type III polyketide synthases (PKSs).

Results

Conclusion