Mechanism of activation of H₂O₂ by peroxidases: kinetic studies on a model system

Abstract

Kinetic studies on the peroxidase activity of microperoxidase-8 at pH 5. 5-8.5 show that the rate is increased by raising the pH or by the presence of guanidinium ion. Comparison with published data on the peroxidases provides evidence that the enzyme activates H202 through the cooperative binding of H+ + HO; and suggests a role for the invariant distal Arg.Peroxidase Proton-coupled reaction Arginine

The coordination of imidazole and substituted pyridines by the hemeoctapeptide N-acetyl-ferromicroperoxidase-8 (FeIINAcMP8)

“…The best characterized of the microperoxidases are MP8 and MP11, which retain 8 and 11 amino acid residues, respectively, of the parent protein. These hemepeptides are useful models for the cytochromes P450 [1], the peroxidases [2][3][4][5][6], and hemoproteins such as myoglobin (Mb) and hemoglobin (Hb) in which heme iron contains a single His axial ligand [7,8]. Aspects of their chemistry have been reviewed [9,10].…”

Microperoxidase/H2O2‐Catalyzed Aromatic Hydroxylation Proceeds by a Cytochrome‐P‐450‐Type Oxygen‐Transfer Reaction Mechanism

“…It contains a heme cofactor that is a protoporphyrin 1X with an iron center that exists in the ferric resting state, and is able to react with hydrogen peroxide to form high-valent iron-oxo intermediates that could be analogous to compounds I and I1 of horseradish peroxidase (Wang and Van Wart, 1989;Wang et al, 1991). The ability of MP8 to catalyze peroxidase-type reactions has been well documented (Cunningham et al, 1991;Baldwin et al, 1985Baldwin et al, , 1987. In addition to the peroxidase behaviour of MP8, it has been claimed that MP8 catalyzes cytochrome-P -450-like reactions such as the hydroxylation of aniline to give 4-aminophenol (Rusvai et al, 1988) and N-demethylations as well as S-oxygenations (Nakamura et al, 1992).…”

Microperoxidase/H 2 O 2 -mediated alkoxylating dehalogenation of halophenol derivatives in alcoholic media

“…It has been shown that MP8 is able to convert a wide variety of organic compounds at the expense of hydrogen peroxide in a peroxidase type of reaction chemistry (3)(4)(5). Furthermore, recent work has demonstrated that MP8, especially in the presence of ascorbic acid, could, like cytochromes P450, mediate oxygen transfer reactions from hydrogen peroxide to substrates (6,7).…”