Advances in the molecular characterization of tryptophan hydroxylase

Susan M. Mockus, Kent Vrana

Research output: Contribution to journalShort survey

71 Citations (Scopus)

Abstract

The neurotransmitter serotonin has been implicated in numerous physiological functions and pathophysiological disorders. The hydroxylation of the aromatic amino acid tryptophan is rate-limiting in the synthesis of serotonin. Tryptophan hydroxylase (TPH), as the rate-limiting enzyme, determines the concentrations of serotonin in vivo. Relative serotonin concentrations are clearly important in neural transmission, but serotonin has also been reported to function as a local antioxidant. Identification of the mechanisms regulating TPH activity has been hindered by its low levels in tissues and the instability of the enzyme. Several TPH expression systems have been developed to circumvent these problems. In addition, eukaryotic expressions systems are currently being developed and represent a new avenue of research for identifying TPH regulatory mechanisms. Recombinant DNA technology has enabled the synthesis of TPH deletions, chimeras, and point mutations that have served as tools for identifying structural and functional domains within TPH. Notably, the experiments have proven long-held hypotheses that TPH is organized into N-terminal regulatory and C-terminal catalytic domains, that serine-58 is a site for PKA-mediated phosphorylation, and that a C-terminal leucine zipper is involved in formation of the tetrameric holoenzyme. Several new findings have also emerged regarding regulation of TPH activity by posttranslational phosphorylation, kinetic inhibition, and covalent modification. Inhibition of TPH by L-DOPA may have implications for depression in Parkinson's disease (PD) patients. In addition, TPH inactivation by nitric oxide may be involved in amphetamine-induced toxicity. These regulatory concepts, in conjunction with new systems for studying TPH activity, are the focus of this article.

Original languageEnglish (US)
Pages (from-to)163-179
Number of pages17
JournalJournal of Molecular Neuroscience
Volume10
Issue number3
DOIs
StatePublished - Jan 1 1998

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Tryptophan Hydroxylase
Serotonin
Phosphorylation
Leucine Zippers
Aromatic Amino Acids
Holoenzymes
Recombinant DNA
Sequence Deletion
Amphetamine
Enzymes
Hydroxylation
Point Mutation
Synaptic Transmission
Tryptophan
Serine
Neurotransmitter Agents
Parkinson Disease
Catalytic Domain
Nitric Oxide
Antioxidants

All Science Journal Classification (ASJC) codes

  • Cellular and Molecular Neuroscience

Cite this

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title = "Advances in the molecular characterization of tryptophan hydroxylase",
abstract = "The neurotransmitter serotonin has been implicated in numerous physiological functions and pathophysiological disorders. The hydroxylation of the aromatic amino acid tryptophan is rate-limiting in the synthesis of serotonin. Tryptophan hydroxylase (TPH), as the rate-limiting enzyme, determines the concentrations of serotonin in vivo. Relative serotonin concentrations are clearly important in neural transmission, but serotonin has also been reported to function as a local antioxidant. Identification of the mechanisms regulating TPH activity has been hindered by its low levels in tissues and the instability of the enzyme. Several TPH expression systems have been developed to circumvent these problems. In addition, eukaryotic expressions systems are currently being developed and represent a new avenue of research for identifying TPH regulatory mechanisms. Recombinant DNA technology has enabled the synthesis of TPH deletions, chimeras, and point mutations that have served as tools for identifying structural and functional domains within TPH. Notably, the experiments have proven long-held hypotheses that TPH is organized into N-terminal regulatory and C-terminal catalytic domains, that serine-58 is a site for PKA-mediated phosphorylation, and that a C-terminal leucine zipper is involved in formation of the tetrameric holoenzyme. Several new findings have also emerged regarding regulation of TPH activity by posttranslational phosphorylation, kinetic inhibition, and covalent modification. Inhibition of TPH by L-DOPA may have implications for depression in Parkinson's disease (PD) patients. In addition, TPH inactivation by nitric oxide may be involved in amphetamine-induced toxicity. These regulatory concepts, in conjunction with new systems for studying TPH activity, are the focus of this article.",
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Advances in the molecular characterization of tryptophan hydroxylase. / Mockus, Susan M.; Vrana, Kent.

In: Journal of Molecular Neuroscience, Vol. 10, No. 3, 01.01.1998, p. 163-179.

Research output: Contribution to journalShort survey

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