Hydrogen peroxide oxidation by catalase‐peroxidase follows a non‐scrambling mechanism

Role of the Oxyferrous Heme Intermediate and Distal Side Adduct Radical in the Catalase Activity of Mycobacterium tuberculosis KatG Revealed by the W107F Mutant

“…The enhanced stability of oxyferrous enzyme in the W107F mutant may depend directly on good hydrogen bonding of the dioxygen ligand with His 108 (48,49 (30). The mechanism of this reaction has not been explained.…”

An Oxyferrous Heme/Protein-based Radical Intermediate Is Catalytically Competent in the Catalase Reaction of Mycobacterium tuberculosis Catalase-Peroxidase (KatG)

“…Among the accumulated mechanistic details for this unusual behavior in a class I peroxidase are the findings of a nonscrambling mechanism shown in isotope-ratio experiments (16), the finding that superoxide is not a product during turnover (16), and the demonstration that mutation of Met 255 , Tyr 229 , or Trp 107 , the side chains of which form the distal side adduct in KatG shown in Fig. 1, reduces the rate thousands-fold (7-10, 14, 36 -38).…”

“…KatG dismutates hydrogen peroxide in a nonscrambling mechanism such that both oxygen atoms of dioxygen derive from the same molecule of hydrogen peroxide (16,17). Unlike classical catalases, however, which do not accumulate intermediates during H 2 O 2 turnover because of very rapid rates of both the peroxide reduction and the peroxide oxidation steps, KatG forms a species characteristic of oxyferrous heme (peroxidase Cmpd III) in the presence of high concentrations of peroxide (11,15,18).…”

Oxidative Processes and Antioxidative Metaloenzymes

“…This non-scrambling mechanism is independent of pH and is not affected by manipulation of highly-conserved and important catalatic residues. Principally, there are two possible mechanisms for the formation of O2 following this retention mechanism: an ionic mechanism, via initial proton abstraction with the help of an acid-base catalyst followed by a hydride-ion removal from H2O2 and release of O2; and hydrogen atom transfer from H2O2 to the ferryl species to yield a radical intermediate [185]. Until now, the complete gene sequences of KatGs were characterised only from prokaryotes (both from archaebacteria and eubacteria) although several reports describe the presence of KatGs in lower eukaryotes [56].…”