Quantifying Metabolic Enzyme Activities

All reagents were of the highest quality available. Bovine serum albumin (fraction V), dithiothreitol (DTT), NAD⁺, l-glutamine, l-asparagine, l-malate, sodium 2-OG, potassium phosphate, hydroxylamine hydrochloride (stock solutions neutralized with NaOH before use), tris hydrochloride, glycine, sodium hydroxide, ferric chloride, lithium lactate, trichloroacetic acid, glycylglycine and protease inhibitor cocktail were obtained from Sigma Aldrich Chemical Company (St. Louis, MO, USA). Succinamic acid was obtained from Aldrich Chemical Company (Milwaukee, WI, USA). 2,4-Dinitrophenylhydrazine was obtained from Eastman Kodak (Rochester, NY, USA). Stock solutions of 2-OGM, in which the pH was adjusted to around 6.0 with NaOH, were prepared by the method of Krasnikov et al. [45 (link)].