creatinephosphocreatine

Creatinephosphocreatine, commonly referred to as phosphocreatine, is the phosphorylated form of the amino acid derivative creatine. It serves as a rapidly mobilizable reserve of high-energy phosphate groups in tissues with fluctuating energy demands, especially skeletal muscle and brain. In the phosphagen system, creatine kinase catalyzes the reversible reaction ATP + creatine ⇌ ADP + phosphocreatine. During short, intense activity, phosphocreatine donates its phosphate to ADP to rapidly regenerate ATP.

In muscle and other tissues, phosphocreatine provides an energy buffer by shuttling high-energy phosphate between mitochondria and the cytosol. When ATP use spikes, the phosphate is donated to ADP to form ATP; when energy demand subsides, ATP is regenerated from phosphocreatine, allowing continued contraction for a few seconds until oxidative phosphorylation or glycolysis increases ATP production.

Endogenous synthesis of creatine begins with glycine and arginine forming guanidinoacetate in the kidney, which is methylated in the liver to produce creatine. Creatine is transported via the bloodstream to tissues and phosphorylated to phosphocreatine by cytosolic or mitochondrial creatine kinases. Creatine and phosphocreatine can be non-enzymatically degraded to creatinine, which is excreted in urine.

Creatine supplementation raises intramuscular phosphocreatine stores and can enhance performance in short, high-intensity efforts for some individuals. It is generally safe for healthy people but may cause weight gain from water retention and is not advised for those with kidney disease without medical supervision. Adequate hydration is often recommended.