<prompt> All of the following are derivatives of tryptophan EXCEPT:MelatoninSerotoninNiacinCreatinine  <response>: 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 