anaplerotic reaction

Anaplerotic reactions are biochemical processes that replenish intermediates of the tricarboxylic acid (TCA) cycle. These reactions are crucial, especially when microorganisms use a single carbon source for energy and biosynthesis.1

When intermediates are removed from the TCA cycle for building cell components, anaplerotic reactions ensure the cycle can continue. This is often achieved by fixing carbon dioxide onto smaller molecules like pyruvate or phosphoenolpyruvate (PEP) to form oxaloacetate, a TCA cycle intermediate. These reactions require energy, typically supplied by ATP.1

Some anaplerotic enzymes are positively modulated by molecules like acetyl coenzyme A, meaning they need this effector to function efficiently. Conversely, they can be inhibited by products that indicate sufficient TCA cycle intermediates are already present. The glyoxylate cycle is another anaplerotic pathway that allows cells to synthesize TCA cycle intermediates from two-carbon compounds like acetate.21