Fumaric acid to malic acid
Conversion of citric acid to cis-aconitic acid
Malic acid to oxaloacetic acid
Oxalosuccinic acid to α-ketoglutaric acid
Oxalosuccinate is decarboxylated to form α-ketoglutarate through the enzyme decarboxylase. It is one of the steps involved in the Krebs cycle. It releases one molecule of CO2. Oxalosuccinate + Decarboxylase → Mg2+ + α-ketoglutarate + CO2