Isocitrate is a six-carbon tricarboxylate related to citrate by the position of a hydroxyl group. This change makes the hydroxyl-bearing carbon available for oxidation.
In the citric acid cycle, oxidative decarboxylation of isocitrate produces 2-Oxoglutarate, releases carbon dioxide, and reduces a nicotinamide cofactor. Isomerization therefore prepares a carbon skeleton for a reaction that its original arrangement does not readily undergo.[ref]
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