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Updated: Sep 5, 2025

Unraveling Entropic Rate Acceleration Induced by Solvent Dynamics in Membrane Enzymes
Published on: January 16, 2016
Single mutations toggle the substrate selectivity of multifunctional Camptotheca secologanic acid synthases
Justin C Miller1, Mary A Schuler2
1Department of Chemistry, University of Illinois Urbana-Champaign, Urbana, Illinois, USA.
Researchers identified key amino acid residues in terpene indole alkaloid (TIA) pathways that control enzyme selectivity. These findings enable tailored production of medicinal compounds like TIAs.
Area of Science:
- Biochemistry
- Plant Science
- Metabolomics
Background:
- Terpene indole alkaloids (TIAs) are crucial plant-derived compounds with significant medicinal applications.
- TIA biosynthesis involves species-specific pathways from common intermediates like strictosidine.
- Secologanin synthase (SLS) and secologanic acid synthase (SLAS) catalyze the penultimate step, but selectivity determinants are unknown.
Purpose of the Study:
- To identify key residues controlling SLS and SLAS selectivity in CYP72A enzymes from Camptotheca acuminata.
- To understand the evolutionary basis of SLS/SLAS selectivity in TIA biosynthesis.
Main Methods:
- Molecular modeling
- Ancestral sequence reconstruction
- Biochemical assays
- Site-directed mutagenesis
Main Results:
- Identified key residues in substrate recognition sequences (SRS1, SRS3, SRS4) that dictate SLS/SLAS selectivity.
- Mutations His131Phe and His132Asp in SRS1 switched enzyme selectivity for secologanin or secologanic acid production, respectively.
- Changes in SRS3 and SRS4 affected overall enzyme activity.
Conclusions:
- Key residues in SRS1, SRS3, and SRS4 are critical for SLS/SLAS selectivity and activity.
- Camptotheca SLASs may retain ancestral broad activity, while other lineages specialized.
- These findings offer pathways for engineering TIAs for heterologous production.
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