In the kidneys, the enzyme AGAT catalyzes the conversion of two amino acids — arginine and glycine — into guanidinoacetate (also called glycocyamine or GAA), which is then transported in the blood to the liver.

Phosphocreatine can anaerobically donate a phosphate group to ADP to form ATP during the first five to eight seconds of a maximal muscular effort.

In other words, phosphocreatine acts as high-energy reserve in a coupled reaction; the energy given off from donating the phosphate group is used to regenerate the other compound - in this case, ATP.

The discovery of phosphocreatine[2][3] was reported by Grace and Philip Eggleton of the University of Cambridge[4] and separately by Cyrus Fiske and Yellapragada Subbarow of the Harvard Medical School[5] in 1927.

A few years later David Nachmansohn, working under Meyerhof at the Kaiser Wilhelm Institute in Dahlem, Berlin, contributed to the understanding of the phosphocreatine's role in the cell.