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Title: Kinetics in microemulsion V. Glucose oxidase catalyzed oxidation of β-D-glucose in aqueous, micellar and water-in-oil microemulsion media
Authors: Gupta, Syamasri
Mukhopadhyay, Lana
Moulik, S P
Keywords: microemulsion
enzyme activity
Issue Date: Oct-2003
Publisher: CSIR
Abstract: The oxidation of β-D-glucose by the enzyme glucose oxidase was studied in aqueous medium, in solutions of surfac-tants AOT (2-ethylhexylsulfosuccinate, sodium salt) TX-100 (polyethylene glycol p-tert octyl phenyl ether) and in w/o mi-croemulsion medium (water/AOT/decane) at different water/AOT mole ratio (ω), pH, temperature and in presence of addi-tives. The time-dependent activities of the enzyme in aqueous and microemulsion media were determined. The catalytic process was retarded in the presence of TX-100 and AOT. In microemulsion medium, k<sub>cat</sub> values exhibited a deformed W-shaped profile with ω. At pH 7, a maximum value of k<sub>cat</sub> was observed at ω = 10.6. The k<sub>cat</sub> values were found to be higher in microemulsion medium than in aqueous medium at both pH’s 7 and 8. Activation parameters for the kinetic process were evaluated together with the thermodynamics of the enzyme-substrate Michaelis complex. The ΔG* was lower, whereas ΔH* and ΔS* were higher in microemulsion than in water. The Michaelis constant, K<sub>M</sub> was also lower in microemulsion. The in-hibition effects of the additives, NaNO<sub>3</sub> and NaC were studied in both aqueous and microemulsion media by examining their influences on catalytic constant, k<sub>cat</sub> and Michaelis constant K<sub>M</sub>. In microemulsion, both the additives NaNO<sub>3</sub> and NaC produced non-competitive inhibition.
Description: 340-349
ISSN: 0301-1208
Appears in Collections:IJBB Vol.40(5) [October 2003]

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