Creatine – How does it work for you?

Creatine is a product of protein metabolism found in muscle. It is synthesized primarily in the liver from three amino acids: glycine, arginine and methionine. It is stored mostly in the skeletal muscles (95%), and the rest in the brain, heart, and testes. The phosphorylated derivative of creatine is called creatine phosphate or phosphocreatine.

The energy for driving most biochemical reactions is derived from the hydrolysis or breakdown of ATP (adenosine triphosphate). To maintain adequate amounts of ATP required for bursts of activity, phosphate is stored as creatine phosphate. The formation of creatine phosphate, which is catalyzed by the enzyme creatine kinase, provides a small but rapidly mobilized reserve of high-energy phosphates that can be used to maintain intracellular level of ATP during the first few minutes of intense muscular contraction. It has been known that creatine phosphate is the compound that is steadily depleted during muscular activity as it donates its phosphate group to ADP (adenosine diphosphate) to form ATP. Therefore, the phosphorylated form of creatine functions as a store of ATP in the muscle.

The amount of creatine phosphate in the body is said to be proportional to muscle mass. Creatine and creatine phosphate are then degraded to creatinine that is excreted in the urine. The amount of creatinine excreted from the body then reflects the total creatine phosphate in the body, which in turn is indicative of how much muscles are in the body. Thus, creatinine in the urine can be used to estimate muscle mass. For example, in cases where there is less muscle mass, such as in paralysis, there will be less creatine phosphate storage and consequently less creatinine in the urine.