n. 肌酸

[ noun ]
an amino acid that does not occur in proteins but is found in the muscle tissue of vertebrates both in the free form and as phosphocreatine; supplies energy for muscle contraction
<noun.substance>

Creatin \Cre"a*tin\ (kr?"?-t?n), n. [Gr. ??? flesh.] (Physiol.
Chem.)
A white, crystalline, nitrogenous substance found abundantly
in muscle tissue. [Written also {kreatine}.]