phosphocreatine

Phosphocreatine, also known as creatine phosphate, is a high-energy phosphorylated compound that acts as a rapidly mobilizable reserve of energy in cells. It is especially abundant in tissues with fluctuating energy demands, such as skeletal muscle, and is also present in the heart and brain.

Phosphocreatine is formed when creatine accepts a phosphate group from ATP via the enzyme creatine kinase, producing phosphocreatine and ADP. During brief, high-intensity activity, the reaction proceeds in the reverse direction: phosphocreatine donates its phosphate to adenosine diphosphate to regenerate ATP, supporting continued muscle contraction. This phosphagen system provides ATP for the initial seconds of intense effort.

In muscle cells, the phosphocreatine/creatine kinase system helps buffer and rapidly supply ATP as needed. Replenishment of the phosphocreatine pool occurs when energy demand decreases and oxidative phosphorylation generates ATP, allowing the phosphate to be transferred back to creatine. Dietary creatine can also contribute to the total creatine/phosphocreatine pool.

Distribution and significance vary by tissue, but in general the phosphocreatine pool represents a substantial portion of cellular energy buffering in tissues with rapid energy turnover. The system works in concert with ATP produced by glycolysis and oxidative metabolism to sustain short bursts of activity and to aid recovery between efforts.

Supplementation with creatine monohydrate increases intramuscular phosphocreatine stores and is used to enhance performance in short, high-intensity activities in many individuals. It is also investigated for potential therapeutic uses in certain metabolic and neuromuscular disorders, under professional guidance.