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Interplay of structural preorganization and conformational sampling in UDP-glucuronic acid 4-epimerase catalysis.

Interplay of structural preorganization and conformational sampling in UDP-glucuronic acid 4-epimerase catalysis.

Authors :
Rapp C
Borg A
Nidetzky B
Source :
Nature communications [Nat Commun] 2024 May 08; Vol. 15 (1), pp. 3897. Date of Electronic Publication: 2024 May 08.
Publication Year :
2024

Abstract

Understanding enzyme catalysis as connected to protein motions is a major challenge. Here, based on temperature kinetic studies combined with isotope effect measurements, we obtain energetic description of C-H activation in NAD-dependent UDP-glucuronic acid C4 epimerase. Approach from the ensemble-averaged ground state (GS) to the transition state-like reactive conformation (TSRC) involves, alongside uptake of heat ( Δ H ‡  = 54 kJ mol <superscript>-1</superscript> ), significant loss in entropy ( - T Δ S ‡  = 20 kJ mol <superscript>-1</superscript> ; 298 K) and negative activation heat capacity ( Δ C p ‡  = -0.64 kJ mol <superscript>-1</superscript> K <superscript>-1</superscript> ). Thermodynamic changes suggest the requirement for restricting configurational freedom at the GS to populate the TSRC. Enzyme variants affecting the electrostatic GS preorganization reveal active-site interactions important for precise TSRC sampling and H-transfer. Collectively, our study captures thermodynamic effects associated with TSRC sampling and establishes rigid positioning for C-H activation in an enzyme active site that requires conformational flexibility in fulfillment of its natural epimerase function.<br /> (© 2024. The Author(s).)

Details

Language :
English
ISSN :
2041-1723
Volume :
15
Issue :
1
Database :
MEDLINE
Journal :
Nature communications
Publication Type :
Academic Journal
Accession number :
38719841
Full Text :
https://doi.org/10.1038/s41467-024-48281-6