fosfokreatin

Fosfokreatin, known in English as phosphocreatine (PCr), is a high-energy phosphate compound that acts as a rapid energy reserve in tissues with high and fluctuating energy demands, especially skeletal muscle and brain. It participates in the creatine kinase reaction, regenerating adenosine triphosphate (ATP) from adenosine diphosphate (ADP) during short, intense activity: PCr + ADP ⇌ Cr + ATP. This buffering helps sustain muscle contraction while aerobic pathways ramp up.

Most creatine in muscle is stored as phosphocreatine, and the phosphocreatine system can respond within seconds to energy needs. The phosphocreatine/ATP buffer is particularly important during abrupt bursts of effort, such as sprinting or heavy lifting, and interacts with glycolytic and mitochondrial energy processes to maintain cellular energy balance.

Creatine is synthesized endogenously from arginine and glycine by arginine:glycine amidinotransferase and is methylated to creatine by guanidinoacetate methyltransferase, mainly in the kidney, liver, and pancreas. It is transported into muscle and other tissues by the creatine transporter (SLC6A8). In tissues, creatine kinase maintains PCr levels and the PCr/ATP ratio during varying energy demands.

In addition to its role in energy buffering, phosphocreatine is studied for implications in brain and heart energy metabolism and certain clinical conditions. Phosphocreatine levels are influenced by dietary creatine supplementation, which can increase intramuscular PCr stores and may enhance performance in short-duration, high-intensity activities; results vary among individuals and contexts.