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Updated: Jun 26, 2026
09:42
Unraveling Entropic Rate Acceleration Induced by Solvent Dynamics in Membrane Enzymes
Published on: January 16, 2016
Analysis of the structural determinants underlying discrimination between substrate and solvent in
Jianying Dai1, Lorenzo Finci, Chunchun Zhang
1Department of Chemistry, University of New Mexico, Albuquerque, New Mexico 87131, USA.
Biochemistry
|January 22, 2009
Summary
This study reveals how beta-phosphoglucomutase (beta-PGM) avoids self-destruction during catalysis. Key residues reposition to stabilize the enzyme, allowing efficient conversion of beta-glucose 1-phosphate to glucose 6-phosphate.
Area of Science:
- Biochemistry
- Enzymology
- Structural Biology
Background:
- Beta-phosphoglucomutase (beta-PGM) is part of the haloacid dehalogenase enzyme superfamily (HADSF).
- It catalyzes the conversion of beta-glucose 1-phosphate (betaG1P) to glucose 6-phosphate (G6P).
- The enzyme uses Asp8 in the core active site for phosphoryl transfer from beta-glucose 1,6-(bis)phosphate (betaG1,6bisP) to betaG1P.
Purpose of the Study:
- To elucidate the mechanism preventing hydrolysis of the phospho-Asp8 intermediate in beta-PGM.
- To understand how the active site remains accessible for substrate and product exchange.
- To investigate the roles of specific residues (Asp10, Thr16, His20, Lys76) in catalysis and enzyme conformation.
Main Methods:
- Structural analysis of beta-PGM.
- Kinetic analyses of site-directed mutants (Asp10, Thr16, His20, Lys76).
- X-ray crystallography of the Thr16 Pro mutant (T16P).
Main Results:
- A catalytic model involving repositioning of the general acid/base Asp10 was proposed.
- Asp10 is crucial for catalysis and stabilizing the cap-closed conformation.
- Thr16 is vital for domain association and preventing phospho-Asp8 hydrolysis.
- His20 and Lys76 are important for substrate-induced cap closure.
- Mutant studies confirmed the roles of these residues in catalysis and enzyme stability.
Conclusions:
- Beta-PGM functions via a substrate-induced fit mechanism.
- Binding of betaG1P triggers Asp10 recruitment and cap domain closure.
- This process ensures efficient catalysis and prevents detrimental intermediate hydrolysis.
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