Biology subjects

Unsworth, W. P.

Publications and source records attributed to Unsworth, W. P..

3 recordsLinked to original sources

bioRxiv2026

Biosynthesis of Securinega alkaloids via a cyanogenic glucoside-like pathway

The elucidation of biosynthetic pathways towards bioactive compounds in plants is essential for building biotechnological platforms for their scalable synthesis. Securinine and allosecurinine form part of the complement of Securinega alkaloids in Flueggea suffruticosa, a fundamental herb of Chinese medicine. Despite their potent biological activities and a growing interest in derivatives as pharmaceutical leads, key steps in their biosynthesis remain obscure. Here we report the discovery and reconstitution of the pathway to the core Securinega alkaloid precursor menisdaurilide. Using transcriptomics, Nicotiana benthamiana transient expression, in vitro assays, and pathway reconstitution in Saccharomyces cerevisiae, we reveal that three cytochrome P450s and a reductase are required for the biosynthesis of menisdaurilide from L-tyrosine via the cyano-metabolite menisdaurigenin, revealing a surprising convergence with the biosynthesis of cyanogenic glucosides such as dhurrin. The de novo biosynthesis of allosecurinine in N. benthamiana highlights the potential for preparative-scale heterologous production of Securinega alkaloids.

biochemistry↗

bioRxiv2024

Nonsymmetric formation of Δ1-piperideine from lysine in plants via a bacterial-like PLP-dependent enzyme

Alkaloids are nitrogen-containing natural products derived from amino acids. The basic amino acids lysine and ornithine are precursors to a wide range of alkaloids including the bioactive compounds nicotine, hyoscyamine and securinine. Feeding experiments have shown that the amino acids can be incorporated into alkaloids in a symmetric or nonsymmetric manner. The symmetric pathway is catalysed by two enzymes, a decarboxylase and oxidase, forming a cyclic iminium which acts as the electrophile in the scaffold forming step. Here, we describe the ornithine/lysine/arginine decarboxylase-oxidases (OLADOs), PLP-dependent enzymes responsible for the nonsymmetric pathway, catalysing the single step decarboxylative oxidative deamination of lysine, ornithine or arginine. These enzymes are group III ornithine/lysine/arginine decarboxylases (OLADs), an enzyme class previously exclusively associated with prokaryotes. We reveal OLADs to be widespread in plants and show that OLADOs have repeatedly emerged through parallel evolution from OLADs, via similar active site substitutions. This investigation introduces a new class of eukaryotic decarboxylases, and describes enzymes involved in multiple alkaloid biosynthesis pathways. It furthermore demonstrates how the principle of parallel evolution at a genomic and enzymatic level can be leveraged for gene discovery across multiple lineages.

biochemistry↗

bioRxiv2022

Integrative metabolomics reveal the organisation of alkaloid biosynthesis in Daphniphyllum macropodum

Daphniphyllum alkaloids are structurally diverse nitrogen-containing compounds with polycyclic, stereochemically rich carbon skeletons. Understanding how plants biosynthesise these compounds may lead to greater access to allow exploration of bioactivities; however, very little is known about their biosynthetic origins. Here, we integrated metabolomics approaches to map alkaloid distribution across Daphniphyllum macropodum plants and tissues. We generated a novel untargeted metabolomics workflow to highlight trends in alkaloid distribution across tissues, using a holistic approach that does not rely on ambiguous peak annotations. Both liquid-chromatography-mass spectrometry and mass-spectrometry imaging analyses independently revealed that alkaloids have a pattern of spatial distribution based on their skeletal subtypes. The distinct alkaloid subtype localisation suggests the biosynthetic pathway is controlled spatially with intermediates transported from the phloem to the epidermis where they undergo additional derivatization. This study sets the stage for the future work on Daphniphyllum alkaloid biosynthesis and highlights how integrating different metabolomics strategies can reveal valuable insights on these compounds distribution within the plant.

plant biology↗