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  • Title: Glyceraldehyde-3-phosphate dehydrogenase as a quinone reductase in the suppression of 1,2-naphthoquinone protein adduct formation.
    Author: Miura T, Shinkai Y, Hirose R, Iwamoto N, Cho AK, Kumagai Y.
    Journal: Free Radic Biol Med; 2011 Dec 01; 51(11):2082-9. PubMed ID: 21963991.
    Abstract:
    1,2-Naphthoquinone (1,2-NQ) is electrophilic, and forms covalent bonds with protein thiols, but its two-electron reduction product 1,2-dihydroxynaphthalene (1,2-NQH(2)) is not, so enzymes catalyzing the reduction with reduced pyridine nucleotides as cofactors could protect cells from electrophile-based chemical insults. To assess this possibility, we examined proteins isolated from the 9000g supernatant from mouse liver for 1,2-NQ reductase activity using an HPLC assay procedure for the hydroquinone of 1,2-NQ and Cibacron Blue 3GA column chromatography and Western blot analysis with specific antibody to determine 1,2-NQ-bound proteins. Among the proteins with high affinities for pyridine nucleotides that also inhibited 1,2-NQ-protein adduct formation in the presence of NADH, a 37-kDa protein was found and identified as glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Using recombinant human GAPDH, we found that this glycolytic enzyme indeed catalyzes the two-electron reduction of 1,2-NQ accompanied by extensive NADH consumption under 20% oxygen conditions. When either 1,2-NQH(2) or 1,2-NQ was incubated with GAPDH in the presence of NADH, minimal covalent bonding to the enzyme occurred compared to that in its absence. These results indicate that GAPDH can inhibit 1,2-NQ-based electrophilic protein modification by conversion to the nonelectrophilic 1,2-NQH(2) via an NADH-dependent process.
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