Ascorbate Reacts with Singlet Oxygen to Produce Hydrogen Peroxide

Abstract

Singlet oxygen is a highly reactive electrophilic species that reacts rapidly with electron-rich moieties, such as the double bonds of lipids, thiols, and ascorbate (AscH-). The reaction of ascorbate with singlet oxygen is rapid (k = 3 × 10 8 M -1 s -1 ). Here we have investigated the stoichiometry of this reaction. Using electrodes to make simultaneous, real-time measurements of oxygen and hydrogen peroxide concentrations, we have investigated the products of this reaction. We have demonstrated that hydrogen peroxide is a product of this reaction. The stoichiometry for the reactants of the reaction (1 1 O 2 + 1AscH-→ 1H 2 O 2 + 1dehydroacorbic) is 1:1. The formation of H 2 O 2 results in a very different oxidant that has a longer lifetime and much greater diffusion distance. Thus, locally produced singlet oxygen with a half-life of 1 ns -1 μs in a biological setting is changed to an oxidant that has a much longer lifetime and thus can diffuse to distant targets to initiate biological oxidations.

Abscisic acid signalling determines susceptibility of bundle sheath cells to photoinhibition in high light-exposed Arabidopsis leaves

“…This situation would quickly lead to the production of other ROS. For example, the reaction of 1 O 2 with the high amount of ascorbate in the chloroplast produces H 2 O 2 under physiologically relevant conditions [37]. This would explain the increased H 2 O 2 observed specifically in HL-exposed BSC chloroplasts [3,4], despite this HL exposure not promoting substantial photoinhibition in the rest of the leaf [3,4,6].…”

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“…that H 2 O 2 could be generated by a specific receptor-ligand interaction in cells and in cell-free systems, although the mechanism of this generation was not well defined. Buettner and co-workers (10,23) showed that ascorbate reacts with singlet oxygen to generate H 2 O 2 , and it is conceivable that Lzm-S could react with singlet oxygen to produce a similar reaction. Recently, NADPH oxidase (Nox4) has been identified in the vasculature as a source of ROS that produces H 2 O 2 (30).…”

Mechanisms of growth inhibition of primary prostate epithelial cells following gamma irradiation or photodynamic therapy include senescence, necrosis, and autophagy, but not apoptosis

“…In order to measure production of H 2 O 2 , one of the most stable reactive oxygen species and the end product of other ROS enzyme reactions , the ROS‐Glo H 2 O 2 Assay (Promega G8820, Southampton, UK) was carried out. Cells were plated in a 96‐well plate (4000–8000 cells per well for whole population and 100–300 cells per well for selected subpopulations).…”