Inosine is a nucleoside involved in the formation of purines and a compound with possible roles in energy metabolism. Inosine is not an amino acid but is classified as a nucleoside, one of the basic compounds comprising cells. It is a precursor to adenosine, an important energy molecule, and plays many supportive roles in the body, including releasing insulin, facilitating the use of carbohydrate by the heart, and, potentially, participating in oxygen metabolism and protein synthesis.It is associated with the development of purines, nonprotein nitrogen compounds that have important roles in energy metabolism. It has been suggested that inosine may improve ATP (Adenosine Tri-Phosphate) production in the muscle and thus be of value to strength athletes. It is also thought to enhance oxygen delivery to the muscles which would benefit endurance athletes.