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Key Message <p><b>A conserved germanicol synthase (GNS) lineage exists in Panax; a single methionine-to-asparagine switch at residue 728 controls triterpene scaffold divergence from β-amyrin to germanicol.</b></p> Abstract <p>Triterpenoid scaffold diversification in <i>Panax</i> is governed by oxidosqualene cyclases (OSCs); however, it remains unclear whether this genus has the ability to produce noncanonical pentacyclic skeletons. In this study, we functionally characterized a previously unrecognized germanicol synthase (PvOSC9) alongside its paralog, β-amyrin synthase (βAS), known as PvOSC8, from <i>Panax vietnamensis</i> var. <i>fuscidiscus</i>. Structural comparisons reveal a single residue 728 (Asn ↔ Met) that alters carbocation folding trajectories, thereby establishing a minimal molecular switch for scaffold identity. Notably, <i>PvOSC9</i> is enriched in flowers and responds to jasmonate, suggesting a possible context-dependent role of <i>PvOSC9</i> in floral tissues. Collectively, these findings broaden the triterpene scaffold repertoire in <i>Panax</i> and offer a mechanistically grounded framework for programmable triterpenoid biosynthesis.</p>

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A conserved germanicol synthase lineage and a single-residue switch controlling triterpene scaffold divergence in Panax

  • 期刊论文

  • 发表日期：

    2026年4月25日

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  • Xue Wang,
  • Jingyang Ding,
  • Shiyan Yuan,
  • Haiyan Li,
  • Yongkang Zhang,
  • Guisheng Xiang,
  • Xianbin Deng,
  • Zihan Yang,
  • Shengchao Yang,
  • Xiaobo Li,
  • Guanghui Zhang

摘要

Key Message

A conserved germanicol synthase (GNS) lineage exists in Panax; a single methionine-to-asparagine switch at residue 728 controls triterpene scaffold divergence from β-amyrin to germanicol.

Abstract

Triterpenoid scaffold diversification in Panax is governed by oxidosqualene cyclases (OSCs); however, it remains unclear whether this genus has the ability to produce noncanonical pentacyclic skeletons. In this study, we functionally characterized a previously unrecognized germanicol synthase (PvOSC9) alongside its paralog, β-amyrin synthase (βAS), known as PvOSC8, from Panax vietnamensis var. fuscidiscus. Structural comparisons reveal a single residue 728 (Asn ↔ Met) that alters carbocation folding trajectories, thereby establishing a minimal molecular switch for scaffold identity. Notably, PvOSC9 is enriched in flowers and responds to jasmonate, suggesting a possible context-dependent role of PvOSC9 in floral tissues. Collectively, these findings broaden the triterpene scaffold repertoire in Panax and offer a mechanistically grounded framework for programmable triterpenoid biosynthesis.