<prompt> The amino acid that can be converted into a vitamin:GlycineTryptophanPhenylalanineLysine  <response>: Ans. B. TryptophanTryptophan can be converted to Niacin.The rate limiting enzyme in Niacin synthesis is Quinolinate Phosphoribosyl Transferase QPRTaseSpecialised products of TryptophanSerotonin 5 HydroxytryptamineMelatoninNiacin 