The biosynthesis of thymol, carvacrol, and thymohydroquinone in Lamiaceae proceeds via cytochrome P450s and a short-chain dehydrogenase

Sandra T. Krause, Pan Liao, Christoph Crocoll, Benoit Boachon, Christiane Förster, Franziska Leidecker, Natalie Wiese, Dongyan Zhao, Joshua C. Wood, C. Robin Buell, Jonathan Gershenzon, Natalia Dudareva, Jörg Degenhardt*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

Thymol and carvacrol are phenolic monoterpenes found in thyme, oregano, and several other species of the Lamiaceae. Long valued for their smell and taste, these substances also have antibacterial and anti-spasmolytic properties. They are also suggested to be precursors of thymohydroquinone and thymoquinone, monoterpenes with anti-inflammatory, antioxidant, and antitumor activities. Thymol and carvacrol biosynthesis has been proposed to proceed by the cyclization of geranyl diphosphate to γ-terpinene, followed by a series of oxidations via p-cymene. Here, we show that γ-terpinene is oxidized by cytochrome P450 monooxygenases (P450s) of the CYP71D subfamily to produce unstable cyclohexadienol intermediates, which are then dehydrogenated by a short-chain dehydrogenase/reductase (SDR) to the corresponding ketones. The subsequent formation of the aromatic compounds occurs via keto-enol tautomerisms. Combining these enzymes with γ-terpinene in in vitro assays or in vivo in Nicotiana benthamiana yielded thymol and carvacrol as products. In the absence of the SDRs, only p-cymene was formed by rearrangement of the cyclohexadienol intermediates. The nature of these unstable intermediates was inferred from reactions with the γ-terpinene isomer limonene and by analogy to reactions catalyzed by related enzymes. We also identified and characterized two P450s of the CYP76S and CYP736A subfamilies that catalyze the hydroxylation of thymol and carvacrol to thymohydroquinone when heterologously expressed in yeast and N. benthamiana. Our findings alter previous views of thymol and carvacrol formation, identify the enzymes involved in the biosynthesis of these phenolic monoterpenes and thymohydroquinone in the Lamiaceae, and provide targets for metabolic engineering of high-value terpenes in plants.

Original languageEnglish
Article numbere2110092118
Number of pages10
JournalProceedings of the National Academy of Sciences of the United States of America
Volume118
Issue number52
DOIs
Publication statusPublished - 20 Dec 2021

Scopus Subject Areas

  • General

User-Defined Keywords

  • Aromatic monoterpenes
  • Carvacrol
  • Lamiaceae
  • Thymohydroquinone
  • Thymol

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