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Updated: Aug 12, 2026

Unraveling Entropic Rate Acceleration Induced by Solvent Dynamics in Membrane Enzymes
Published on: January 16, 2016
The phenomenon of super activity in dihydrofolate reductase entrapped inside reverse micelles in apolar solvents
S S Katiyar1, A Kumar, A Kumar
1Department of Chemistry, Indian Institute of Technology, Kanpur.
Abstract:
Bovine liver dihydrofolate reductase has been solubilized in reverse micelles of cationic surfactant cetyltrimethylammonium bromide (CTAB) in isooctane-chloroform (1:1,V/V) mixture. Variation of waterpool (WO), pH and surfactant concentration showed that the enzyme activity was regulated by these parameters and was higher than the activity found in aqueous buffer (defined as superactivity); the maximum being at WO 13.3, pH 7.0 and CTAB concentration 75 mM. The Michaelis constants, Km for the substrate FAH2 and NADPH were found to be greater than those determined in water. Since reverse micelles have some features similar to those of biomembranes, display of super activity by dihydrofolate reductase indicates that enzymes in vivo may possess higher activity than actually observed in vitro studies in aqueous solutions.
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