Immediate precursor of creatine

Creatine constitutes about 0.5% of total muscle weight.It is synthesized from 3 aminoacids, glycine,arginine and methionine. STEP 1 :In the first reaction the amidino group of arginine is transferred to glycine to form guanidoacetic acid,catalysed by amido transferase. STEP 2 :Guanidoacetic acid is methylated by S-adenosyl methionine (SAM) bt methyl transferase to form creatine. STEP 3 :Creatine is phosphorlated to creatine phosphate.The reaction needs hydrolysis of ATP. STEP 4 :The creatine phophate may be conveed to its anhydride, creatinine.It is a non-enzymatic spontaneous reaction. REF :DM VASUDEVAN TEXTBOOK ;7th EDITION ; Page no :211