Hydrogen peroxide

About: Hydrogen peroxide is a research topic. Over the lifetime, 42583 publications have been published within this topic receiving 1043732 citations. The topic is also known as: H2O2 & dioxidane.

I. glutathione peroxidase, an erythrocyte enzyme which protects hemoglobin from oxidative breakdown*

Abstract: Although the exact mechanism of the conversion of hemoglobin into biliverdin in vivo is still in doubt, the most plausible route is through the oxidation and opening of the tetrapyrrole ring, after which the globin and iron are removed. This reaction scheme is based on the extensive chemical studies of Lemberg and Legge (1) and on the more recent work of Kaziro el al. (2-4). In these studies, the oxidation of the tetrapyrrole ring was brought about under physiological conditions of pH and temperature by a coupled oxidation with ascorbic acid. Presumably, ascorbic acid reacts with the oxygen of oxyhemoglobin to produce a constant supply of hydrogen peroxide. This, in turn, oxidizes either the iron or the tetrapyrrole ring of hemoglobin. Two distinct intermediates are produced in this chemical breakdown of hemoglobin. Choleglobin, which is formed first, has a distinctive absorption band at 627 to 630 rnp after treatment with carbon monoxide and sodium hydrosulfite. As the reaction proceeds further, the appearance of an absorption band at 760 rnp is indicative of the presence of verdohemoglobin. Treatment with glacial acetic acid and ether will quantitatively convert verdohemoglobin into biliverdin. One of the problems of hemoglobin catabolism has been the explanation of the remarkable stability of hemoglobin in the intact cell to materials which would ordinarily destroy it, Ascorbic acid is a normal constituent of the red blood cell, and hydrogen peroxide presumably is generated constantly in small amounts within the cell. Even oxygen brings about a rather rapid autoxidation of hemoglobin in solutions of crystalline oxyhemoglobin (5). Foulkes and Lemberg (6) and Kaziro and coworkers (2) have previously shown the importance of catalase in protecting hemoglobin from oxidative breakdown produced by ascorbic acid. In addition, Foulkes and Lemberg (6) have shown that catalase will give some protec

Factors Influencing the Antioxidant Activity Determined by the ABTS•+ Radical Cation Assay

Abstract: (1997). Factors Influencing the Antioxidant Activity Determined by the ABTS•+ Radical Cation Assay. Free Radical Research: Vol. 26, No. 3, pp. 195-199.

Involvement of Hydrogen Peroxide in the Regulation of

Abstract: Endogenous peroxide levels in pear fruit (Pyrus communis) were measured using a titanium assay method, and were found to increase during senescence in both Bartlett and Bosc varieties. Application of glycolic acid or xanthine, serving as substrates for the formation of H202, increased the peroxide content of the tissue and accelerated the onset of ripening, as measured by increased softening and ethylene evolution. Application of ethylene also induced increased peroxide levels. Ripening processes were similarly promoted when peroxides were conserved by inhibiting the activity of catalase with hydroxylamine or potassium cyanide. By comparison, the inhibition of glycolate oxidase with alphahydroxy-2-pyridinemethanesulfonic acid decreased the peroxide content of the tissue and delayed the onset of ripening. These results indicate that the onset of ripening correlates with the peroxide content of fruit tissues as occurring under normal conditions or as influenced by the treatments. Hydrogen peroxide may be involved in oxidative processes required in the initiation and the promotion of ripening.