Stabilization of glucoso-6-phosphate dehydrogenase by its substrate and cofactor in an ultrasonic field
| Autor: | E. I. Karaseva, D. I. Metelitza |
|---|---|
| Rok vydání: | 2006 |
| Předmět: |
Sonication
Inorganic chemistry Glucose-6-Phosphate Dehydrogenase Glucosephosphate Dehydrogenase Biochemistry Cofactor Substrate Specificity chemistry.chemical_compound Reaction rate constant Enzyme Stability Ultrasonics chemistry.chemical_classification Aqueous solution biology Organic Chemistry Temperature Water Substrate (chemistry) Phosphate Solutions Enzyme chemistry biology.protein Thermodynamics Physical chemistry Leuconostoc NADP |
| Zdroj: | Russian Journal of Bioorganic Chemistry. 32:436-443 |
| ISSN: | 1573-9163 1068-1620 |
| Popis: | The inactivation kinetics of glucoso-6-phosphate dehydrogenase (GPDH) and its complexes with glucoso-6-phosphate and NADP+ was characterized in aqueous solutions at 36–47°C under treatment with low frequency (27 kHz, 60 W/cm2) and high frequency ultrasound (880 kHz, 1 W/cm2). To this end, we measured three effective first-order inactivation rate constants: thermal k in * , total (thermal and ultrasonic) k in, and ultrasonic k in(US). The values of the constants were found to be higher for the free enzyme than for its complexes GPDH-GP and GPDH-NADP+ at all temperatures, which confirms the enzyme stabilization by its substrate and cofactor under both thermal and ultrasonic inactivation. Effective values of the activation energies (E a) were determined and the preexponential factors of the rate constants and thermodynamic activation parameters of inactivation processes (ΔH*, ΔS*, and ΔG*) were calculated from the temperature dependences of the inactivation rate constants of GPDH and its complexes. The sonication of aqueous solutions of free GPDH and its complexes was accompanied by a reduction of E a and ΔH* values in comparison with the corresponding values for thermal inactivation. The E a, ΔH*, and ΔS* inactivation values for GPDH are lower than the corresponding values for its complexes. A linear dependence between the growth of the ΔH* and ΔS* values was observed for all the inactivation processes for free GPDH and its complexes. |
| Databáze: | OpenAIRE |
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