MMUT (Methylmalonyl-CoA Mutase) is a gene that encodes a mitochondrial enzyme essential for energy metabolism. It catalyzes the conversion of methylmalonyl-CoA to succinyl-CoA, a key step in the breakdown of certain amino acids and fatty acids. This reaction supports the citric acid cycle and overall cellular energy production. Mutations in MMUT can lead to methylmalonic acidemia (MMA), a rare metabolic disorder marked by toxic buildup of methylmalonic acid in the body.