Biosynthesis of Ephedrine Initiated by Pyridoxal Phosphate‐Dependent Formation of Cathinone

TL;DR

This study reveals a new pathway for the biosynthesis of ephedra alkaloids, using a PLP-dependent enzyme to form cathinone, bypassing a previously assumed intermediate.

Contribution

The paper identifies a novel PLP-dependent pathway for ephedra alkaloid biosynthesis involving cathinone formation.

Findings

A PLP-dependent carboligation of benzoyl-CoA and l-alanine forms (S)-cathinone in Ephedra and Catha edulis.

Labeled nitrogen from l-alanine is incorporated into (S)-cathinone, supporting the role of an α-oxoamine synthase.

The proposed pathway bypasses the 1-phenylpropane-1,2-dione intermediate previously thought essential.

Abstract

Ephedra alkaloids possess some of the most basic structures of alkaloids. Despite their importance for human use and their commercial relevance, the biosynthesis of ephedra alkaloids has remained enigmatic. The predominant biosynthetic pathway in the literature proposes a thiamin‐dependent carboligation followed by a transaminase, although no candidate enzymes have yet been identified in ephedra alkaloid producers. In this work, an alternative pathway in plants to ephedra alkaloids via (S)–cathinone is investigated that circumvents the formation of 1‐phenylpropane‐1,2‐dione as an intermediate and is in full agreement with previous biosynthetic studies. This alternative pathway involves the pyridoxal phosphate (PLP)‐dependent carboligation of –benzoyl‐CoA– and l‐alanine in a single step. The PLP‐dependent formation of labeled and unlabeled (S)–cathinone is detected in the plant lysate of young stem tissue of various Ephedra species that contain Ephedra alkaloids, as well as in young leaf tissue of Catha edulis. The incorporation of labeled nitrogen from l‐alanine into (S)‐cathinone supports the hypothesis that an α‐oxoamine synthase (AOS) catalyzes the formation of (S)‐cathinone, bypassing the dione as an intermediate. These results demonstrate the involvement of a PLP‐dependent AOS as a pivotal step in the biosynthesis of ephedra alkaloids.

An alternative pathway to ephedra alkaloids via (S)–cathinone is investigated in plants. This pathway circumvents the formation of 1‐phenylpropane‐1,2‐dione as an intermediate, which has been part of the predominantly postulated biosynthetic pathway for the last decades. This alternative pathway involves an enzymatic pyridoxal phosphate (PLP)‐dependent carboligation of benzoyl‐CoA and l‐alanine in a single step.© 2025 WILEY‐VCH GmbH

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