This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
The composition of creatine is: 
Select and explain. 
A. Glycine, arginine, methionine, B. Glycine and histidine, C. Glycine, glutamate, aspartate, D. Histidine and methionine
A: Glycine, arginine, methionine
Answer: A: Glycine, arginine, methionine 
Explanation: Ans. (a) Glycine, arginine, methionineRef: Vasudevan Biochemistry, 8th ed. P 269* Creatinine is formed in muscle from creatine phosphate by irreversible, nonenzymatic dehydration and loss of phosphate.* Glycine, arginine, and methionine all participate in creatine biosynthesis.* Synthesis of creatine is completed by methylation of guanidinoacetate by S-adenosylmethionine.