References

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Enzyme catalysis by ferryl ion and free radicals

Table 1 shows examples of all enzyme species known, or suggested, to utilise ferryl intermediates. It is the high redox potential of the Fem FeIV couple that results in the variety of its uses in biology. In cytochrome oxidases this potential provides a useful bridge between the Fem Fen cytochrome c couple and that of O2 H2O, resulting in a mechanism that allows redox energy to be converted into a vectorial proton electrochemical potential. In the peroxidases the ferryl species is used to...

Anthony T Diplock

United Medical and Dental Schools, Free Radical Research Group, Division of Biochemistry, Guy s & St. Thomas's Hospital, St. Thomas Street, London, UK SE1 9RT 1.1. Definitions of antioxidants An antioxidant may be defined as any substance which can delay or prevent the oxidation of a substrate when it is present in small amounts relative to the amount of the substrate. Halliwell and Gutteridge 1 considered that antioxidants act at several different levels in the oxidative sequence, and that...

Protective pathways of mammalian cells and tissues

To prevent an overload in free radicals and peroxides, aerobic organisms use a sophisticated defense system which operates both in the intra- and extracellular aqueous phases and in membranes. A detailed description of the extracellular protections is outside the scope of this chapter. Cell protections may be divided into hydrophobic and hydrophilic molecular systems. Hydrophobic protective systems include vitamin E, i.e. a-tocopherol which, as all chromanol compounds, is a free radical...

Roh

A comparison of peroxidase, cytochrome c oxidase and cytochrome P-450 reaction mechanisms. Peroxidase mechanism adapted from that of Poulos 143 , cytochrome P-450 mechanism adapted from that of Sligar 100 , and cytochrome oxidase mechanism adapted from that of Babcock and Wikstrom 90 . RH, organic substrate for peroxidase and cytochrome P-450 (in the latter case the substrate is presumed to remain bound to the enzyme through most of the reaction cycle). e.g. the homologous bacterial...

Catalase[ Felv O H202 Catalase Fe III H202

The significance of catalase in the overall prevention of oxygen-derived free radical damage is difficult to decide with precision because of the doubt about the intracellular localization of the enzyme. If it is indeed only sequestered within peroxisomes its principal, or even only, function may be to catalyse the reduction of H2O2 that arises as a direct consequence of the metabolic activity of the peroxisome itself. However, H2O2 can cross membranes and it may be that, when intracellular...

List of contributors

Cardiothoracic Surgery, Medical College of Wisconsin, Milwaukee, WI 53226, USA Senior Lecturer, Department of Biological Sciences, University of Wollongong, Northfield's Ave., Wollongong, NSW 2522, Australia Inflammation Research Group, The London Hospital Medical College, University of London, Turner Street, London, UK El 2AD R.H. Burdon, 155 Department of Bioscience & Biotechnology, The Todd Centre, University of Strathclyde, Glasgow, Scotland, UK G4 ONR J. Chaudi re, 25 Centre de...