N-methyl-N-(N-phosphonocarbamimidoyl)glycine

142.8 Ų [M+Na-2H]- [CCS Type: DT; Method: single field calibrated with ESI Low Concentration Tuning Mix (Agilent)]

153.77 Ų [M+H]+ [CCS Type: DT; Method: stepped-field]

144.4 Ų [M+H]+ [CCS Type: DT; Method: single field calibrated with Agilent tune mix (Agilent)]

144.8 Ų [M+H]+

Creatine is a naturally occurring chemical within the body and is primarily stored in skeletal muscle in both free and phosphorylated forms. Phosphocreatine is the name given to the phosphorylated form of creatine. Additionally, phosphocreatine can also be found in other areas of the body like the kidneys, liver, and brain. In fact, most *in vivo* synthesis of creatine occurs in the liver where amidine groups from arginine are transfered to glycine with the help of the glycine transaminidase enzyme to form guanidinoacetic acid. This acid is then methylated with the methyl group of S-adenosylmethionine via guanidinoacetate methyltransferase to generate creatine. The synthesized creatine is transported to storage sites in skeletal muscle via the bloodstream. The phosphorylation of creatine is reversible in both a forwards and backwards reaction. That is, while phosphocreatine is capable of anaerobically donating a phosphate group to adenosine diphosphate (ADP) to regenerate ATP, at the same time excess ATP can be dephosphorylated during periods of low muscle activity to convert creatine to phosphocreatine. This dual activity in synthesizing phosphocreatine from excess levels of ATP during rest and use of phosphocreatine to regenerate ATP during high activity demonstrates the crucial utility of phosphocreatine in acting as an energy buffer in body mucle cells. Phosphocreatine's fast regeneration of ATP is considered a coupled reaction - in essence, the energy released from transferring a donating a phosphate group from phosphocreatine is used to regenerate ATP. Phosphocreatine consequently plays an essential role in body tissues that have high, fluctuating energy requirments like muscle and brain tissues.

Adenosine triphosphate (ATP) is the primary source of chemical energy that body muscles use to perform contractions. During such contraction processes, ATP molecules are depleted as they undergo hydrolysis reactions and become adenosine diphosphate (ADP). To maintain homeostasis in muscle activity, the ATP supply of muscles must be regenerated regularly. Phosphocreatine occurs naturally within the body and is capable of regenerating ATP by transferring a high-energy phosphate from itself to ADP, resulting in the formation of ATP and creatine. This kind of regeneration of ATP with phosphocreatine typically occurs within seconds of intense muscular or neuronal effort, acting as a quickly accessible reserve of high-energy phosphates for the recycling of ATP in body muscle tissues. ATP recycling from phosphocreatine is in fact known as the quickest form of ATP regeneration.

Phosphocreatine is eliminated renally. The end result of creatine degredation is the product creatinine, which enters the bloodstream from its storage sites in body muscle. When creatinine enters the renal parenchyma it is filtered in the renal glomerulus to be excreted in the urine.