Functions of the Redox-Active Metal Sites in This Enzyme

Functions of the Redox-Active Metal Sites in This Enzyme 

Nevertheless, the redox difference spectra of the two hemes are consistent with those predicted from the coordination (or spin state) of the hemes. That is, a strong and sharp hemochrome-type peak is observed at 605 nm for the difference spectrum of heme a, while heme as exhibits a weak absorption in the visible region. Redox difference spectra of the two hemes are quite similar in the Soret region, showing intense positive bands at 445 nm and negative bands at 410 25 nm. Many kinetic results have been analyzed with the extinction coefficients given by Vanneste (1966). 

The absorption spectrum of Cua in the visible-Soret region is much weaker than the spectra of the two hemes. However, it is well established that Cua in the oxidized state contributes to the broad absorption band near 830 nm significantly (Wharton and Tzagoloff, 1964 Beinert et al., 1980). However, the contribution of heme a to the 830-nm band should not be ignored (Caughey et al., 1976). 

A spectral characterization of Cub has not been reported except for an EPR signal detectable in the presence of a reducing system and O2 where presumably Cub is in the cupric state and Fea is in the ferric state (Reinhammer et al., 1980). 

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V. Functions of the Redox-Active Metal Sites in This Enzyme. 358... 

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