Hydrogen peroxides, bands characteristic

RSSF techniques have been used extensively to study the catalytic mechanisms of both peroxidases and catalases (117-127). This class of enzymes are ferri(Fe III)-hemoproteins that exhibit characteristic a, 3, and Soret spectral bands in the 400- to 600-nm region of the visible spectrum. These spectral bands are generally indicative of a high-spin nonplanar Fe heme prosthetic group. Peroxidases and catalases utilize either alkyl peroxides (Equation 5, where AH2 represents a wide variety of reducing substrates) or hydrogen peroxide (Equation 6) as substrates, respectively. 

As for other peroxidases, a high-valent iron-oxo entity associated with a porphyrin 7r-radical-cation, Cpd I, is generated by the addition of hydrogen peroxide (see Scheme 3 for the catalytic cycle of LiP). This green compound (Soret band at 408 nm) has UV-visible and EPR characteristics similar to that of HRP-Cpd 1. ... 

Catalase has been studied intensively by chemical and physical methods. The protein component is not unusual in amino acid composition. The iron appears to be present only in the ferric form, and cannot be reduced chemically by any procedure that does not denature the enzyme. There is evidence, however, that during an enzymatic reaction with hydrazoic acid and hydrogen peroxide the iron is reduced to the ferrous state. The iron forms compounds with a large number of molecules. Some of these, such as HCN, HNs, and H2S, are inhibitors of the enzyme. The absorption spectrum of catalase shows bands at 403 m/i (Soret), 500 m/i, 540 m/B, and 629 m/t . These shift to give characteristic spectra when HCN, HN3, or HF combines with enzyme. Magnetic... 

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