Reduction and inactivation of superoxide dismutase by hydrogen peroxide

Abstract

Reactions of H(2)O(2) with superoxide dismutase were studied by e.p.r. (electron paramagnetic resonance) spectroscopy and other methods. In agreement with earlier work, the Cu(2+) of the enzyme is reduced by H(2)O(2), although the reaction does not go to completion and its kinetics are not simple. With dilute enzyme the time for half-reduction with 9mm-H(2)O(2) is about 150ms. It is suggested that the reaction is a one-electron reduction, involving liberation of O(2) (-). On somewhat more prolonged exposure to H(2)O(2), the enzyme is inactivated. For enzyme in dilute solution and over a limited range of H(2)O(2) concentrations, inactivation is first-order with respect to enzyme and reagent, with k=3.1m(-1).s(-1) at 20-25 degrees C. Inactivation is accompanied by marked changes in the e.p.r. and visible spectra and appears to be associated with destruction of one histidine residue per subunit. It is suggested that this histidine is close to the metal in the native enzyme and essential for its enzymic activity.

A pulse-radiolysis study of the catalytic mechanism of the iron-containing superoxide dismutase from Photobacterium leiognathi

“…9 F. LAVELLE ANI) OTHERS signals were seen (cf. bovine Cu-superoxide dismutase; Bray et al, 1974). Hachimori et al (1964 have shown that H202 reacts with aromatic amino acids, either in free solution or as residues in proteins (e.g.…”

“…However, this reaction mechanism may not be simple and the second-order rate constant quoted may apply only under the stated conditions (cf. bovine erythrocyte enzyme; Bray et al, 1974).…”

Copper-dependent metabolism of Cu,Zn-superoxide dismutase in human K562 cells. Lack of specific transcriptional activation and accumulation of a partially inactivated enzyme

“…H202 has been proposed to inactivate Cu,Zn-SOD by causing the hydroxylation of a copper-ligating histidine [40,41]. This results in a reduced metal affinity and, consequently, in the detachment of copper [42].…”

Action of protoporphyrin-IX (PP-IX) in the lifespan of <i>Drosophila melanogaster</i> deficient in endogenous antioxidants, Sod and Cat

“…The most accepted hypothesis of aging was proposed by Gerschman [15] and Harman [1] who suggest that aging results from the accumulation of damage caused by free radicals; this is supported with evidence found by different systems [16][17][18][19][20][21]. The use of strains deficient in the expression of endogenous antioxidants has been practicable in testing the effect of dietary antioxidants in lifespan.…”

“…Drosophila melanogaster has been extensively used to test the effect of dietary exogenous antioxidants in lifespan because it offers many advantages: its lifespan is short, 80 -90 days (in laboratory conditions) and no mitotic divisions take place in the adult [22]. In addition, different mutant strains in genes involved in antioxidant defense such as catalase and superoxide dismutase enzymes could be used [16,20]. It is known that through the lifespan of Drosophila the activity of Cat decreases [18,[23][24][25] however, the increased expression of the Cat gene does not extend the lifespan of flies, but rather protects against oxidative stress [26].…”