This is very clear from the rare hereditary diseases where creatine synthesis is impossible due to the malfunctioning of either l-Arginine:glycine amidinotransferase (less commonly known as “glycine amidinotransferase, mitochondrial”) (AGAT or, less commonly, GATM) or Guanidinoacetate methyltransferase (GAMT), the two enzymes that catalyze creatine synthesis from arginine, glycine and S-adenosyl-methionine [34]. Here, GATM is linked to hereditary disease.