Methylmalonyl

Methylmalonyl refers to a chemical moiety or a salt/ester derived from methylmalonic acid. Methylmalonic acid is a dicarboxylic acid with the formula CH3CH(COOH)2. It is an isomer of malonic acid, where a methyl group is attached to the central carbon atom. In biological contexts, methylmalonyl is particularly significant as it is a product of the catabolism of certain amino acids, specifically valine, isoleucine, threonine, and methionine.

The metabolism of methylmalonyl plays a crucial role in the body. The methylmalonyl-CoA mutase enzyme, which requires vitamin B12 as a cofactor, catalyzes the isomerization of methylmalonyl-CoA to succinyl-CoA. Succinyl-CoA is an intermediate in the citric acid cycle, a central pathway for energy production. A deficiency in vitamin B12 impairs this conversion, leading to an accumulation of methylmalonyl-CoA and methylmalonic acid in the body. This accumulation can be detected in blood and urine and is a diagnostic marker for vitamin B12 deficiency.

Elevated levels of methylmalonic acid (MMA) can indicate metabolic disorders. Beyond vitamin B12 deficiency, certain genetic disorders affecting the methylmalonyl-CoA mutase enzyme itself, known as methylmalonic acidemias, can also cause significantly high MMA levels. These conditions can lead to severe health problems, including neurological damage, developmental delays, and metabolic crises if not managed. Therefore, monitoring methylmalonyl levels is important in clinical diagnostics for both nutritional deficiencies and inherited metabolic diseases.