Creatine phosphate

Creatine phosphate (also known as phosphocreatine) is a molecule that serves as a rapid and readily available energy reserve in the body. It is especially important in tissues that have high, fluctuating energy demands such as muscle and brain.

Overview

Creatine phosphate is synthesized in the liver, kidneys, and pancreas from the amino acids arginine, glycine, and methionine. Once synthesized, it is transported to the muscle cells, where it is stored until needed. During periods of high energy demand, creatine phosphate donates its phosphate group to ADP to form ATP, the body's primary energy currency. This reaction is catalyzed by the enzyme creatine kinase.

Role in Muscle Contraction

In muscle cells, the energy for contraction is initially supplied by ATP. However, the ATP stores in the muscle are limited and can only sustain contraction for a few seconds. To continue contracting, the muscle must regenerate ATP. One of the primary ways this is accomplished is through the creatine phosphate system.

When the muscle is at rest, excess ATP donates its phosphate group to creatine, forming creatine phosphate. This reaction is reversible, so when the muscle starts to contract and the ATP levels drop, creatine phosphate can quickly donate its phosphate group back to ADP to form ATP. This allows the muscle to continue contracting even when the ATP stores are depleted.

Clinical Significance

Abnormal levels of creatine phosphate in the blood can be an indicator of certain medical conditions. High levels can indicate muscle damage, as the creatine phosphate leaks out of the damaged muscle cells into the bloodstream. Low levels can indicate a problem with the body's energy metabolism.

Creatine phosphate is also used in some diagnostic tests. For example, the creatine kinase-MB test measures the level of a specific form of creatine kinase in the blood, which can help diagnose a heart attack.

See Also

• Creatine
• ATP
• Muscle Contraction
• Creatine Kinase
• Energy Metabolism

References

Creatine phosphate Resources
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