Selectivity of oxidase and reductase activity of horse heart cytochrome c |
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Authors: | Y P Myer K K Thallum J Pande B C Verma |
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Affiliation: | The Institute of Hemoproteins, Department of Chemistry State University of New York at Albany, Albany, NY 12222 USA |
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Abstract: | The ascorbate-TMPD-cytochrome oxidase and succinate cytochrome reductase activities and the redox potentials of native and chemically modified cytochromes with modification of Trp-59 and Met-65, nitro-cytochrome with modification of Tyr-67, and a new preparation, Chloramine-T-cytochrome m with modification of Met-80 and -65 to methionine sulfoxide—have been compared at pH 7.8 in 25 mM cacodylate-Tris buffer. These modifications exhibit (i) a slight lowering of redox potential, from 260 mV to 180, 215 and 170 mV, respectively, (ii) destabilization of the cytochrome -reductase complex, 6 to 12 fold, but without alteration of the cytochrome -oxidase complex, and (iii) a slight lowering of the maximum velocity for both the oxidase and reductase reactions. The selective destabilization of the cytochrome -reductase complex is interpreted as an indication of a two-path, two-function model for the oxido-reduction function of cytochrome . |
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