Catalases photochemical reactions

There is no direct evidence for participation of radical pairs in the reaction of catalase, but a radical pair is known to be formed through thermal or photochemical homolysis of alkylcob(ni)alamins (RCbl ) from ps-laser photolysis experiments. The structure of adenosyl-cob(ni)alamin (AdoCbP) and metylcob(III)alamin (MetCbl ) and the radical pair produced from RCbl are shown in Fig. 15-1. Vitamin B12 is a cofactor for many enzymatic reactions in its various forms. 

It should be noted that the iron centre in porphyrins can be oxidized to high oxidation states, notably in the reactions of peroxidase and catalase. These oxidizing equivalents may rest on the porphyrin ring, generating 7r-radical cations. Such radical cations can be generated chemically, electrochemically and photochemically. Thus a triplet ESR spectrum has been observed for a copper porphyrin radical cation produced by y-radiolysis in tetrachloroethane at 77 K. In this case, one electron was localized in the Sd -y orbital of the copper, and the other was delocalized in the highest occupied ir-orbital of the porphyrin ring. ... 

Using the photochemical flux of OJ for activity staining of gels, one interfering reaction is often overlooked. In the presence of hydrogen peroxide, catalase yields also achromatic bands. Owing to the reactivity of catalase (Eq. (4)) this phenomenon must be seen in the local rise of the pO ... 

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