With help of pyridoxine, serotonin is synthesized from which of the following precursor amino acid?

Serotonin is synthesized from the essential amino acid tryptophan. The rate-limiting step is the conversion of the amino acid to 5-hydroxytrptophan by tryptophan hydroxylase. This is then conveed to serotonin by the aromatic L-amino acid decarboxylase. 5-hydroxyindoleacetic acid (5-HIAA). This substance is the principal urinary metabolite of serotonin. There are seven classes of 5-HT receptors (from 5-HT1 through 5-HT7 receptors). Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 7. Neurotransmitters & Neuromodulators. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.