An Unexpected Oxidosqualene Cyclase Active Site Architecture in the Iris tectorum Multifunctional α-Amyrin Synthase

Shidan Wu, Fan Zhang, Wenbo Xiong, István Molnár, Jincai Liang, Aijia Ji, Yu Li, Caixia Wang, Shengliang Wang, Zhongqiu Liu, Ruibo Wu, Lixin Duan

Research output: Contribution to journalArticlepeer-review

Abstract

Ordered polycyclization catalyzed by oxidosqualene synthases (OSCs) morph a common linear precursor into structurally complex and diverse triterpene scaffolds with varied bioactivities. We identified three OSCs from Iris tectorum. ItOSC2 is a rare multifunctional α-amyrin synthase. Sequence comparisons, site-directed mutagenesis, and multiscale simulations revealed that three spatially clustered residues, Y531/L256/L258, form an unusual Y-LL triad at the active site, replacing the highly conserved W-xY triad occurring in other amyrin synthases. The discovery of this active site architecture in ItOSC2 underscores the plasticity of terpene cyclase catalytic mechanisms and opens avenues for protein engineering toward custom designed OSCs.

Original languageEnglish (US)
Pages (from-to)9515-9520
Number of pages6
JournalACS Catalysis
Volume10
Issue number16
DOIs
StatePublished - Aug 21 2020

Keywords

  • QM/MM
  • enzyme catalysis
  • enzyme promiscuity
  • oxidosqualene cyclase
  • triterpene

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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