Creatine Synthesis from the Amino Acids: Arginine, Glycine and Methionine

Legend: Reaction 1 (catalyzed by AGAT) is the rate limiting step in creatine biosynthesis. AGAT expression is also reduced by the presence of creatine. This raised concerns that prolonged creatine supplementation might inhibit endogenous creatine synthesis for an indefinite period of time. See Chapter 16 of my creatine guide for greater discussion of the implications of this effect.

Finally, notice that Glycine is completely incorporated into the creatine backbone, whereas Arginine and Methionine only contribute side groups.