Methylmalonyl-CoA is a biochemical compound that plays a crucial role in the metabolism of certain amino acids and fatty acids. It is formed from the breakdown of valine, isoleucine, threonine, and methionine, as well as from the metabolism of odd-chain fatty acids. In the body, methylmalonyl-CoA is converted into succinyl-CoA through the action of the enzyme methylmalonyl-CoA mutase. This conversion is essential for energy production and the proper functioning of various metabolic pathways, particularly in the Krebs cycle, which generates energy for cellular activities.