A compound that is phosphorylated to phosphocreatine,
which represents a store of high-energy phosphoryl
groups in muscle that can be transferred to ADP, yielding ATP
for muscle contraction. The enzyme involved in phosphate
transfer between them is creatine phosphokinase that catalyzes
the reaction
Phosphocreatine+ADP→ATP+creatine
An increase in serum creatine phosphokinase may be indicative
of damage to non-hepatic tissue but not to the liver.
Creatine is an amino acid that occurs naturally in dairy products, seafood, and beef. It is manufactured by the body in the liver, kidney, and pancreas.
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Creatine is used for gyrate atrophy, McArdle's disease, muscular dystrophy, amyotrophic lateral sclerosis, and rheumatoid arthritis. It is used in congestive heart disease to improve exercise tolerance and to enhance athletic performance.
Purification Methods
Likely impurities are creatinine and other guanidino compounds. It crystallises from the minimum volume of boiling H2O as the monohydrate. The hydrate is also obtained by dissolving in H2O and adding Me2CO. Drying under vacuum over P2O5 or drying at 100o gives the anhydrous base. The anhydrous base can be obtained also by dissolving the hydrate in H2O, seeding with the anhydrous base and cooling in ice. A m of 258 -268o(dec) was reported. The picrate crystallises from 17 parts of H2O with m of 218-220o(dec). [King J Chem Soc 2377 1930, Hoffmann et al. J Am Chem Soc 58 1730 1936, Mendel & Hodgkin Acta Cryst 7 443 1954, Greenstein & Winitz The Chemistry of the Amino Acids J. Wiley, Vol 3 p 2750 1961, Beilstein 4 III 1170, 4 IV 2425.]
