Carbamoylation of Cu,Zn-superoxide dismutase by cyanate: Role of lysines in the enzyme action |
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Authors: | Dina Cocco Luisa Rossi Donatella Barra Francesco Bossa Giuseppe Rotilio |
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Institution: | 1. Department of Biochemistry, The University of Mississippi Medical Center, Jackson, MS 39216 USA;2. Department of Biochemistry, Medical University of South Carolina, Charleston, SC 29425 USA |
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Abstract: | Reaction with cyanate leads to a reversible change of the EPR spectrum of Cu,Zn-superoxide dismutase and to time-dependent carbamoylation of the lysine residues of the enzyme, producing a stable covalent derivative with more negative charge. The carbamoylated enzyme is less active than the native enzyme in spite of unaltered EPR spectra. The extent of this inactivation is much less when the enzyme activity is measured at low ionic strength. These results show that integrity of the active site is not the sole factor playing a role in the enzyme mechanism and that the ionic strength effect is related to electrostatic interactions between O−2 and surface charges of the protein. |
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Keywords: | Superoxide dismutase Carbamoylation Lysine neutralization Electrostatic interactions in enzyme catalysis Ionic strength effect on enzymes |
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