Creatine phosphate or phosphocreatine is a phosphorylated creatinine molecule which serves as an energy source for muscle fibers of the skeletal muscle and neurons in the brain. It is composed out of parts of three amino acids: arginine, glycine and methionine. Creatine phosphate is synthesized in the liver and is transported to the muscle cells through the bloodstream. High energy phosphates are transported by a specific shuttle from the mitochondria.
These phosphates are kept available in pools within tissues for conversion of adenosine diphosphate (ADP) to adenosine triphosphate (ATP) to be used as an immediate source of energy for muscle contraction. The conversion allows for a spatial as well as temporal buffer of ATP concentrations. This reversible process is called phosphorylation and is catalyzed by the enzyme creatine phosphokinase. It occurs during the first 2 to 7 seconds following intense muscle contraction. This makes it a suitable source of phosphate for tissues that have a high energy demand.
In a state of rest, stores of creatine phosphate are rebuilt, also through the dephosphorylation of ATP. Also the photoreceptor cells of the retina use these creatine phosphate stores. Creatine kinases exist in different forms and are also used in tests to diagnose heart and kidney failure, muscle disorders and brain damage. High creatine kinase levels can indicate increased uptake of statin drugs, while low levels are a marker for rheumatoid arthritis and alcohol damage. The discovery of the high energy potential of creatine phosphate allowed the development of various applications in anabolic foods.