<P> Creatine is not an essential nutrient as it is naturally produced in the human body from the amino acids glycine and arginine . In the first step of the biosynthesis these two amino acids are combined by the enzyme arginine : glycine amidinotransferase ( AGAT , EC : 2.1. 4.1 ) to form guanidinoacetate , which is then methylated by guanidinoacetate N - methyltransferase ( GAMT , EC : 2.1. 1.2 ) , using S - adenosyl methionine as the methyl donor . Creatine itself can be phosphorylated by creatine kinase to form phosphocreatine , which is used as an energy buffer in skeletal muscles and the brain . </P>
where does creatine come from in the body
glycine arginine