ESR investigations of free and immobilized glutamate dehydrogenase |
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Authors: | O'Connor K C Bailey J E |
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Institution: | Department of Chemical Engineering, California Institute of Technology, Pasadena, California 91125. |
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Abstract: | The structure of bovine liver glutamate dehydrogenase was examined with 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl (TEMPO I) and 4-((4-(chloromercurio)benzoyl) amino)-2, 2, 6, 6-tetramethyl-1-piperidinyloxy (TEMPO II). ESR spectra from TEMPO I show that enzyme structure in the vicinity of this spin label was not distorted during immobilization to a Sepharose support. Deactivation studies with pyridoxal 5'-phosphate indicate that immobilization did not expose additional binding sites to TEMPO I. Spectra from TEMPO II reveal that immobilization profoundly altered conformational change induced by alpha-ketoglutarate and suppressed that induced by GTP and NADPH. This structural investigation provides insight into the altered kinetic properties of Sepharose-immobilized glutamate dehydrogenase and suggests a fundamental difference between monomers and allosteric oligomers in their structural response to immobilization. |
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