Functional domains of human tryptophan hydroxylase 2 (hTPH2)

Nurgul Carkaci-Salli, John M. Flanagan, Matthew K. Martz, Ugur Salli, Diego J. Walther, Michael Bader, Kent E. Vrana

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Abstract

Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in serotonin biosynthesis. A novel gene, termed TPH2, has recently been described. This gene is preferentially expressed in the central nervous system, while the original TPH1 is the peripheral gene. We have expressed human tryptophan hydroxylase 2 (hTPH2) and two deletion mutants (NΔ150 and NΔ150/CΔ24) using isopropyl β-D-thiogalactopyranoside-free autoinduction in Escherichia coli. This expression system produced active wild type TPH2 with relatively low solubility. The solubility was increased for mutants lacking the NH 2-terminal regulatory domain. The solubility of hTPH2, NΔ150, and NΔ150/ CΔ24 are 6.9, 62, and 97.5%, respectively. Removal of the regulatory domain also produced a more than 6-fold increase in enzyme stability (t1/2 at 37°C). The wild type hTPH2, like other members of the aromatic amino acid hydroxylase superfamily, exists as a homotetramer (236 kDa on size exclusion chromatography). Similarly, NΔ150 also migrates as a tetramer (168 kDa). In contrast, removal of the NH2-terminal domain and the COOH-terminal, putative leucine zipper tetramerization domain produces monomeric enzyme (39 kDa). Interestingly, removal of the NH2-terminal regulatory domain did not affect the Michaelis constants for either substrate but did increase Vmax values. These data identify the NH 2-terminal regulatory domain as the source of hTPH2 instability and reduced solubility.

Original languageEnglish (US)
Pages (from-to)28105-28112
Number of pages8
JournalJournal of Biological Chemistry
Volume281
Issue number38
DOIs
StatePublished - Sep 22 2006

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Solubility
Genes
Enzymes
Thiogalactosides
Tryptophan Hydroxylase
Enzyme Stability
Leucine Zippers
Aromatic Amino Acids
Size exclusion chromatography
Biosynthesis
Neurology
Mixed Function Oxygenases
Escherichia coli
Gel Chromatography
Serotonin
Central Nervous System
human TPH2 protein
Substrates

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Carkaci-Salli, Nurgul ; Flanagan, John M. ; Martz, Matthew K. ; Salli, Ugur ; Walther, Diego J. ; Bader, Michael ; Vrana, Kent E. / Functional domains of human tryptophan hydroxylase 2 (hTPH2). In: Journal of Biological Chemistry. 2006 ; Vol. 281, No. 38. pp. 28105-28112.
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abstract = "Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in serotonin biosynthesis. A novel gene, termed TPH2, has recently been described. This gene is preferentially expressed in the central nervous system, while the original TPH1 is the peripheral gene. We have expressed human tryptophan hydroxylase 2 (hTPH2) and two deletion mutants (NΔ150 and NΔ150/CΔ24) using isopropyl β-D-thiogalactopyranoside-free autoinduction in Escherichia coli. This expression system produced active wild type TPH2 with relatively low solubility. The solubility was increased for mutants lacking the NH 2-terminal regulatory domain. The solubility of hTPH2, NΔ150, and NΔ150/ CΔ24 are 6.9, 62, and 97.5{\%}, respectively. Removal of the regulatory domain also produced a more than 6-fold increase in enzyme stability (t1/2 at 37°C). The wild type hTPH2, like other members of the aromatic amino acid hydroxylase superfamily, exists as a homotetramer (236 kDa on size exclusion chromatography). Similarly, NΔ150 also migrates as a tetramer (168 kDa). In contrast, removal of the NH2-terminal domain and the COOH-terminal, putative leucine zipper tetramerization domain produces monomeric enzyme (39 kDa). Interestingly, removal of the NH2-terminal regulatory domain did not affect the Michaelis constants for either substrate but did increase Vmax values. These data identify the NH 2-terminal regulatory domain as the source of hTPH2 instability and reduced solubility.",
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Functional domains of human tryptophan hydroxylase 2 (hTPH2). / Carkaci-Salli, Nurgul; Flanagan, John M.; Martz, Matthew K.; Salli, Ugur; Walther, Diego J.; Bader, Michael; Vrana, Kent E.

In: Journal of Biological Chemistry, Vol. 281, No. 38, 22.09.2006, p. 28105-28112.

Research output: Contribution to journalArticle

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T1 - Functional domains of human tryptophan hydroxylase 2 (hTPH2)

AU - Carkaci-Salli, Nurgul

AU - Flanagan, John M.

AU - Martz, Matthew K.

AU - Salli, Ugur

AU - Walther, Diego J.

AU - Bader, Michael

AU - Vrana, Kent E.

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N2 - Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in serotonin biosynthesis. A novel gene, termed TPH2, has recently been described. This gene is preferentially expressed in the central nervous system, while the original TPH1 is the peripheral gene. We have expressed human tryptophan hydroxylase 2 (hTPH2) and two deletion mutants (NΔ150 and NΔ150/CΔ24) using isopropyl β-D-thiogalactopyranoside-free autoinduction in Escherichia coli. This expression system produced active wild type TPH2 with relatively low solubility. The solubility was increased for mutants lacking the NH 2-terminal regulatory domain. The solubility of hTPH2, NΔ150, and NΔ150/ CΔ24 are 6.9, 62, and 97.5%, respectively. Removal of the regulatory domain also produced a more than 6-fold increase in enzyme stability (t1/2 at 37°C). The wild type hTPH2, like other members of the aromatic amino acid hydroxylase superfamily, exists as a homotetramer (236 kDa on size exclusion chromatography). Similarly, NΔ150 also migrates as a tetramer (168 kDa). In contrast, removal of the NH2-terminal domain and the COOH-terminal, putative leucine zipper tetramerization domain produces monomeric enzyme (39 kDa). Interestingly, removal of the NH2-terminal regulatory domain did not affect the Michaelis constants for either substrate but did increase Vmax values. These data identify the NH 2-terminal regulatory domain as the source of hTPH2 instability and reduced solubility.

AB - Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in serotonin biosynthesis. A novel gene, termed TPH2, has recently been described. This gene is preferentially expressed in the central nervous system, while the original TPH1 is the peripheral gene. We have expressed human tryptophan hydroxylase 2 (hTPH2) and two deletion mutants (NΔ150 and NΔ150/CΔ24) using isopropyl β-D-thiogalactopyranoside-free autoinduction in Escherichia coli. This expression system produced active wild type TPH2 with relatively low solubility. The solubility was increased for mutants lacking the NH 2-terminal regulatory domain. The solubility of hTPH2, NΔ150, and NΔ150/ CΔ24 are 6.9, 62, and 97.5%, respectively. Removal of the regulatory domain also produced a more than 6-fold increase in enzyme stability (t1/2 at 37°C). The wild type hTPH2, like other members of the aromatic amino acid hydroxylase superfamily, exists as a homotetramer (236 kDa on size exclusion chromatography). Similarly, NΔ150 also migrates as a tetramer (168 kDa). In contrast, removal of the NH2-terminal domain and the COOH-terminal, putative leucine zipper tetramerization domain produces monomeric enzyme (39 kDa). Interestingly, removal of the NH2-terminal regulatory domain did not affect the Michaelis constants for either substrate but did increase Vmax values. These data identify the NH 2-terminal regulatory domain as the source of hTPH2 instability and reduced solubility.

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