Antigen: phosphopeptide corresponding to amino acid residues surrounding phospho-Ser⁵⁸ of TPH · Host: rabbit · Application(s): WB · Tryptophan hydroxylase (TPH) catalyzes the 5-hydroxylation of tryptophan, which is the first step in the biosynthesis of indoleamines (serotonin and melatonin).¹ In mammals, serotonin biosynthesis occurs predominantly in neurons which originate in the Raphe nuclei of the brain, and melatonin synthesis takes place within the pineal gland. Although TPH catalyzes the same reaction within the Raphe nuclei and the pineal gland, TPH activity is rate-limiting for serotonin but not melatonin biosynthesis. Serotonin functions mainly as a neurotransmitter, whereas melatonin is the principal hormone secreted by the pineal gland. The activity of TPH is enhanced by phosphorylation by cAMP-dependent protein kinase (PKA) and Ca2+/calmodulin kinase II (CaM K II).^2,3 Both PKA and CaM K II phosphorylate Ser⁵⁸ which lies within the regulatory domain of TPH.⁴

1 Martinez, A., Knappskog, P.M., and Haavik, J. A structural approach into human tryptophan hydroxylase and its implications for the regulation of serotonin biosyntheis. Curr Med Chem 8 1077-1091 (2001).

2 Jiang, G.C., Yohrling, G.J., Schmitt, J.D., et al. Identification of substrate orienting and phosphorylation sites within typtophan hydroxylase using homology-based molecular modeling. J Mol Biol 302 1005-1017 (2000).

3 Johansen, P.A., Jennings, I., Cotton, R.G., et al. Phosphorylation and activation of tryptophan hydroxylase by exogenous protein kinase A. J Neurochem 66 817-823 (1996).

4 Kuhn, D.M., Arthur, R., and States, J.C. Phosphorylation and activation of brain tryptophan hydroxylase: Identification of serine-58 as a substrate site for protein kinase A. J Neurochem 68 2220-2223 (1997).

Martinez, A., Knappskog, P.M., and Haavik, J. A structural approach into human tryptophan hydroxylase and its implications for the regulation of serotonin biosyntheis. Curr Med Chem 8 1077-1091 (2001).

Johansen, P.A., Jennings, I., Cotton, R.G., et al. Phosphorylation and activation of tryptophan hydroxylase by exogenous protein kinase A. J Neurochem 66 817-823 (1996).

Kuhn, D.M., Arthur, R., and States, J.C. Phosphorylation and activation of brain tryptophan hydroxylase: Identification of serine-58 as a substrate site for protein kinase A. J Neurochem 68 2220-2223 (1997).

Jiang, G.C., Yohrling, G.J., Schmitt, J.D., et al. Identification of substrate orienting and phosphorylation sites within typtophan hydroxylase using homology-based molecular modeling. J Mol Biol 302 1005-1017 (2000).

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