The Separation between Cytochrome A and Cytochrome A3 in the Absolute Spectrum
aa3-Type cytochrome was purified from Halobacterium halobium (1). The cytochrome contained two heme a molecules per molecule but no copper. It did not show cytochrome c oxidase activity. One of the two heme a molecules in the cytochrome was reduced with ascorbate + TMPD, while the other was not reduced with this reducing reagents. The heme a molecule reducible with ascorbate + TMPD did not react with CO, while the heme a molecule reducible only with Na2S2O4 reacted with CO. Therefore, cytochrome a. or heme aA in the cytochrome was separated from cytochrome a3 or heme aB on the reduction with ascorbate + TMPD; the γ peaks of ferrocytochrome a and ferricytochrome a3 were observed spectrophotometrically in the absolute spectrum. As CuA is known to be unnecessary for cytochrome aa3 to oxidize ferrocytochrome c (2), these results mentioned above show that copper atom, CuB mediate electrons between heme aA and heme aB.
KeywordsCopper Atom Difference Spectrum Nitrosomonas Europaea Halobacterium Halobium Absolute Spectrum
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