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Spectral and kinetic abnormality during the reduction of cytochrome c 3 catalyzed by hydrogenase ec 1.12.2.1 with hydrogen






Biochimica et Biophysica Acta 767(2): 288-294

Spectral and kinetic abnormality during the reduction of cytochrome c 3 catalyzed by hydrogenase ec 1.12.2.1 with hydrogen

Reduction process of [Desulfovibrio vulgaris] cytochrome c3 by hydrogenase under H2 was analyzed by means of spectrophotometry. When cytochrome c3 is in equilibrium with H2 under reduced pressure, spectral abnormality in the Soret region appeared most significantly at 1/4 reduction state, less significantly at 1/2 reduction state, and disappeared at 3/4 reduction state. The spectral changes during the enzymic reduction of cytochrome c3 in H2-saturated solution traced at several wavelengths also showed spectral abnormality in the Soret region at the early stage of reaction. The 1st-order rate constants for the successive reduction steps from all-ferric to all-ferrous form of cytochrome c3 was estimated to be k1 = 0.061 s-1, k2 = 0.063 s-1, k3 = 0.039 s-1 and k4 = 0.014 s-1 (cytochrome c3: 2 .mu.M; hydrogenase: 2 nM, and at 20.degree. C, pH 7.0). Strong interaction is suggested between hemes 3 and 4 (for the refined structure and heme-numbering, see Higuchi et al.). The 1st electron from hydrogenase is supposed to be transferred to these hemes and delocalized between them, and the 2nd electron, among hemes 3, 4 and 1. The characteristic behavior in the enzymic reduction of cytochrome c3 is different from that in non-enzymic reduction.


Accession: 006459501



Related references

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