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(creatine phosphate, creatine phosphoric acid), a product of creatine phosphorylation; an energy-rich compound.
Phosphocreatine was first discovered in 1927 in fresh specimens of muscle tissue. It can be prepared by treating creatine with POCI3 in an alkaline medium. One of the energy sources for muscle contraction is the readily reversible decomposition of phosphocreatine, catalyzed by the enzyme creatinase: phosphocreatine + ADP ⇄ creatine + ATP. A decrease in the ATP content in the tissues leads to the decomposition of phosphocreatine; an increase in ATP content leads to its synthesis. Thus, phosphocreatine forms a reserve of energy-rich phosphate, both the phosphate and stored energy of which can be used in the formation of ATP. In tissues, phosphocreatine undergoes gradual spontaneous decomposition to yield inorganic phosphate and creatinine, which is eliminated with the urine. Arginine phosphate replaces phosphocreatine in many invertebrates (for example, insects).
N. P. MESHKOVA