All are tryptophan derivatives except-

Ans. is 'a' i.e., MelaninAmino acidsBiological important compoundTyrosineCatecholamines (epinephrine, norepinephrine, dopamine), thyroxine, triiodothryonine, melanin.(Note : - Phenylalanine is the precursor of tyrosine, thus it can also give rise to all these compounds through tyrosine (phenylalanine - Tyrosine - Catecholamines, thyroxine, T3' melanin).TryptophanVitamin niacin, melatonin, SerotoninGlycine, Arginine, methionineCreatineGlycine, cysteineBile saltsGlycineHemeAspartic acid and glutaminePyrimidine basesGlycine, aspartic acid, glutaminePurine basesb-alanineCoenzyme-AArginineNitric oxideHistidine, Arginine, lysineKeratinMethionine, lysineCarnitineGABAGlutamateGlutamate, cysteine, glycineGlutathione