Fumaric acid uses the fumarase enzyme to become malic acid. Malate dehydrogenase catalyzes the conversion of malic acid into oxaloacetate. Two forms of this enzyme exist in eukaryotes. One operates within the mitochondria to contribute to the Citric Acid Cycle; the other is in the cytosol where it participates in the malate/ aspartate shuttle. Riboflavin is an important cofactor for this enzyme and overall mitochondrial energy production and cellular function. At the end of each Citric Acid Cycle, the four-carbon oxaloacetate has been regenerated, and the cycle continues.
References:
- Minarik P, Tomaskova N, Kollarova M, Antalik M. Malate dehydrogenases-structure and function. Gen Physiol Biophys. 2002;21(3):257-266.
- Depeint F, Bruce WR, Shangari N, Mehta R, O’Brien PJ. Mitochondrial function and toxicity: role of the B vitamin family on mitochondrial energy metabolism. Chemico-biol Interact. 2006;163(1-2):94-112.
- Kim D CJ, Cheng T, Gindulyte A, He J, He S, Li Q, Shoemaker BA, Thiessen PA, Yu B, Zaslvasky L, et. al. PubChem 2019 update: improved access to chemical data. Nucleic Acids. 2019.
Malic Acid
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