Apparent negative co-operativity and substrate inhibition in overexpressed glutamate dehydrogenase from Escherichia coli |
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Authors: | Sharkey Michael A Engel Paul C |
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Affiliation: | UCD School of Biomolecular and Biomedical Sciences, Conway Institute, University College Dublin, Belfield, Dublin, Republic of Ireland |
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Abstract: | The gene for Escherichia coli glutamate dehydrogenase (EcGDH) has been overexpressed, and a simplified purification procedure afforded greatly increased yields of c. 40 mg pure EcGDH L−1 culture. EcGDH was unstable at a low concentration in plastic tubes, but stabilization measures allowed a robust kinetic characterization. Contrary to past reports, EcGDH deviates from Michaelis–Menten kinetics, exhibiting apparent mild negative co-operativity with both l -glutamate and NADP+, with Hill coefficients of 0.90 and 0.92, respectively. NADPH yielded simple Michaelis–Menten kinetics but both 2-oxoglutarate and NH4+ showed substrate inhibition. pH optima were 9 for oxidative deamination and 8 for reductive amination. |
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Keywords: | glutamate dehydrogenase Escherichia coli overexpression enzyme purification substrate inhibition negative co-operativity |
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