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
[{'content': 'All of the following are derivatives of tryptophan EXCEPT: \nSelect and explain. \nA. Melatonin, B. Serotonin, C. Niacin, D. Creatinine', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. (d) Creatinine* Tryptophan is one of the essential aromatic amino acid* Metabolic fate of tryptophan: Metabolized by enzyme Tryptophan oxygenase (pyrrolase)* Derivatives of tryptophan:# Niacin (Nicotinic acid)# Serotonin# Melatonin* Note: Creatinine is synthesized from 3 amino acids namely: Glycine, Arginine. Methionine', 'role': 'assistant'}]