Reducing agent mediated non-enzymatic conversion of 2-oxoglutarate to succinate - implications for oxygenase assays.

L-Ascorbate (L-Asc) is often added to assays with isolated Fe(II) and 2-oxoglutarate (2OG) dependent oxygenases to enhance activity. L-Asc is proposed to be important in catalysis by some 2OG oxygenases in vivo. We report observations on the non-enzymatic conversion of 2OG to succinate which is mediated by hydrogen peroxide (H2O2), generated by reaction of L-Asc and dioxygen. Slow non-enzymatic oxidation of 2OG to succinate occurs with some, but not all, other reducing agents commonly used in 2OG oxygenase assays. We intend the observations will help in the robust assignment of substrates and inhibitors for 2OG oxygenase.