Creatine

Creatine ( or ) is an organic compound that facilitates recycling of adenosine triphosphate (ATP) in vertebrates, primarily in their muscle and brain tissue. It is a popular dietary supplement of limited if any benefit.

Its phosphorylated form, phosphocreatine, donates phosphate groups to adenosine diphosphate (ADP), turning it back into ATP. Creatine also acts as a buffer. It has the nominal formula (H₂N)(HN)CN(CH₃)CH₂CO₂H. In solutions, it exists in various tautomers, including a neutral form and zwitterionic forms.