<unk>  ( or ) is an organic compound with the nominal formula (H2N)(HN)CN(CH3)CH2CO2H. It exists in various modifications (tautomers) in solution.<unk>  is found in vertebrates where it facilitates recycling of adenosine triphosphate (ATP), primarily in muscle and brain tissue. Recycling is achieved by converting adenosine diphosphate (ADP) back to ATP via donation of phosphate groups.<unk>  also acts as a buffer.
Creatine
Inositol
Beta-Hydroxy beta-methylbutyric acid
Phenylacetic acid
Choline
Phosphine
High-energy phosphate
Glycogen