Studies on the Reduction of Dehydroascorbic Acid by Glutathione in the Presence of Aquahydroxocobinamide

Abstract

This study reports that aquahydroxocobinamide [(H 2 O)(HO -)Cbi(III)], a nucleotide-free analogue of cobalamin (vitamin B 12 ; Cbl), is capable of catalyzing the reduction of the two-electron oxidized form of vitamin C, dehydroascorbic acid (DHA), to ascorbic acid by glutathione (GSH), whereas catalytic quantities of aquacobalamin do not accelerate the reaction. This observation is explained by different reactions taking place [a]

Cobinamide is a strong and versatile antioxidant that overcomes oxidative stress in cells, flies, and diabetic mice

“…As part of these studies, we found that Cbi(III) is readily reduced to Cbi(II) by ascorbate, cysteine, and reduced glutathione (GSH) under physiological conditions (Fig. 3G ) [previous workers have also found that GSH reduces Cbi(III) to Cbi(II) ( 41 )]. The implications of the facile reduction of Cbi(III) to Cbi(II) will be considered in the “Discussion” section.…”

Versatile enzymology and heterogeneous phenotypes in cobalamin complementation type C disease

“…Cobinamides are corrinoids lacking the dimethylbenzyimidazole moiety of cobalamin. Aquahydroxocobin(III)amide undergoes reduction to cobin(II)amide in the presence of GSH ( Dereven’kov et al., 2018 ). Glutathionylcobalamin, formed by the reaction of GSH with hydroxocobalamin, in spite of possessing a bulky β-ligand, does not undergo the aforementioned reduction.…”

“…In the case of the interaction between MMADHC and cob(II)alamin⋅MMACHC, a cob(II)alamin thiolate complex is formed. Although rare examples of labile Co(II)-corrinoid-thiolate complexes are known ( Cockle et al., 1972 ; Dereven’kov et al., 2018 , 2017 ), intraprotein Co(II)-S interaction is significantly tighter. Both MMACHC-bound cob(II)alamin or MMADHC-bound cob(III)alamin could initiate the formation of the interprotein complex between MMACHC and MMADHC, yet kinetics favor the former in line with the established cobalamin processing sequence.…”

A Modification of the ABTS• Decolorization Method and an Insight into Its Mechanism

“…The interactions were observed when studying concentration dependence of absorbance decrease and AUC (Table 4). These subadditive effects in ABTS • scavenging might be ascribed to the reported interactions between vitamin E and ascorbate, vitamin E and flavonoids [50,51], and ascorbate and glutathione [52,53]. These interactions were postulated to consist in the reduction of tocopheryl radicals by ascorbate or flavonoids, and reduction of ascorbate free radical and ascorbate by glutathione.…”