Activity of EFE with the alternative oxo-acid substrate, 2OA. The remaining substrates and the formation of products are shown for a representative time course during a 2 mL reaction containing 504 nM EFE, 0.3 mM 2OA, 0.5 mM L-Arg, 0.2 mM Fe(II), and 0.4 mM L-ascorbic acid in 10 mM NH4HCO3, pH 7.5, at 25 °C. Error bars represent standard errors for n = 2.