Heme peroxidases

DET calculations on the hyperfine coupling constants of ethyl imidazole as a model for histidine support experimental results that the preferred histidine radical is formed by OH addition at the C5 position [00JPC(A)9144]. The reaction mechanism of compound I formation in heme peroxidases has been investigated at the B3-LYP level [99JA10178]. The reaction starts with a proton transfer from the peroxide to the distal histidine and a subsequent proton back donation from the histidine to the second oxygen of the peroxide (Scheme 8). 

Dunford, H.B. (1999) Heme Peroxidases, Wiley-VCH Verlag GmbH, New York pp. 323-348. 

Relationships in Heme Peroxidases Ann M. English and George Tsaprailis... 

The enzymatic reactions of peroxidases and oxygenases involve a two-electron oxidation of iron(III) and the formation of highly reactive [Fe O] " species with a formal oxidation state of +V. Direct (spectroscopic) evidence of the formation of a genuine iron(V) compound is elusive because of the short life times of the reactive intermediates [173, 174]. These species have been safely inferred from enzymatic considerations as the active oxidants for several oxidation reactions catalyzed by nonheme iron centers with innocent, that is, redox-inactive, ligands [175]. This conclusion is different from those known for heme peroxidases and oxygenases... 

The class II secreted fungal heme peroxidases include the LMPs LiP, MnP and VP [70]. All of these enzymes are extracellular and contain protoporphyrin IX (heme) as prosthetic group. They use H2O2 or organic hydroperoxides as electron accepting cosubstrates during the oxidation of diverse compounds. They are secreted as glycosilated, 35-38 kDa size proteins. 

Meunier, B. Models of Heme Peroxidases and Catalases , Imperial College Press London, 2000 pp. 171-214. 

Martinez AT (2002) Molecular biology and structure-function of lignin-degrading heme peroxidases. Enzyme Microb Technol 30 425 144... 

The mechanism of free radical formation in the reactions catalyzed by MPO and other heme peroxidase may be presented as follows [180] ... 

The heme peroxidases oxidize a variety of structurally diverse substrates by using hydrogen peroxide or hydroperoxides as oxidants, whereby the oxidants are reduced to water or alcohol. In the following, the present state of such peroxidase-catalyzed reactions in organic synthesis is described, which unquestionably is important for preparative work. 

The heme peroxidase superfamily of enzymes catalyzes the H2O2-dependent oxidation of a wide variety of substrates ... 

Dunford, H. B. Heme Peroxidases John Wiley Chichester, 1999. 

Vanadoproteins are found in most marine algae and seaweed and in some lichens.616 Among these are haloperoxidases,252 253 617 618b enzymes that are quite different from the corresponding heme peroxidases discussed in Section A,6. The vanadium is bound as... 

NADH peroxidase (p. 857, Eq. 15-59) does not contain a transition metal ion. Propose a reasonable detailed mechanism for its action and compare it with mechanisms of action of heme peroxidases. 

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