Abstract
(1) Reduction process of cytochrome c 3 by hydrogenase (EC 1.12.2.1) under H 2 was analyzed by means of spectrophotometry. (2) When cytochrome c 3 is in equilibrium with H 2 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 2 4 reduction state. (3) The spectral changes during the enzymic reduction of cytochrome c 3 in H 2-saturated solution traced at several wavelengths also showed spectral abnormality in the Soret region at the early stage of reaction. (4) The first-order rate constants for the successive reduction steps from all-ferric to all-ferrous form of cytochrome c 3 was estimated to be k 1 = 0.061s −1, k 2 = 0.063s −1, k 3 = 0.039s −1 and k 4 = 0.014s −1 (cytochrome c 3: 2 μM; hydrogenase: 2 nM, and at 20°C, pH 7.0). (5) Strong interaction is suggested between hemes 3 and 4 (for the refined structure and heme-numbering, see Higuchi, Y., Kusunoki, M., Matsuura, Y., Yasuoka, N. and Kakudo, M. (1984) J. Mol. Biol. 172, 109–139). (6) The first electron from hydrogenase is supposed to be transferred to these hemes and delocalized between them, and the second electron, among hemes 3, 4 and 1. (7) The characteristic behavior in the enzymic reduction of cytochrome c 3 is different from that in non-enzymic reduction.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call