Phosphocreatine can anaerobically donate a phosphate group to
ADP to form
ATP during the first 2 to 7 seconds following an intense muscular or neuronal effort. Conversely, excess
ATP can be used during a period of low effort to convert
creatine to phosphocreatine. The reversible phosphorylation of creatine (i.e., both the forward and backward reaction) is catalyzed by several
creatine kinases. The presence of creatine kinase (
CK-MB, MB for muscle/brain) in
plasma is indicative of tissue damage and is used in the diagnosis of myocardial infarction.
[1] The cell's ability to generate phosphocreatine from excess
ATP during rest, as well as its use of phosphocreatine for quick regeneration of
ATP during intense activity, provides a spatial and temporal buffer of
ATP concentration. In other words, phosphocreatine acts as high-energy reserve in a coupled reaction; the energy given off from donating the phosphate group is used to regenerate the other compound - in this case,
ATP. Phosphocreatine plays a particularly important role in tissues that have high, fluctuating energy demands such as muscle and brain.
