Tryptophan Hydroxylase Is Phosphorylated by Protein Kinase A

Patricia A. Johansen, Ian Jennings, Richard G H Cotton, Donald M. Kuhn

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Abstract: The effect of protein kinase A on the catalytic activity and phosphorylation of brain tryptophan hydroxylase was examined. Stimulation of endogenous protein kinase A by cyclic AMP or its analogues, dibutyryl‐cyclic AMP and 8‐thiomethyl‐cyclic AMP, failed to activate tryptophan hydroxylase. The activation of tryptophan hydroxylase by calcium/calmodulin‐phosphorylating conditions was not modified by cyclic AMP. Endogenous protein kinase A phosphorylated a large number of proteins and tryptophan hydroxylase could be identified as one substrate by sucrose gradient centrifugation, immunoprecipitation, and immunoblotting. These results indicate that tryptophan hydroxylase is phosphorylated by protein kinase A in brain and question whether this protein kinase exerts direct regulatory influence over tryptophan hydroxylase activity via phosphorylation.

Original languageEnglish
Pages (from-to)882-888
Number of pages7
JournalJournal of Neurochemistry
Issue number2
Publication statusPublished - 1 Jan 1995
Externally publishedYes


  • Brain
  • Calcium/calmodulin phosphorylation
  • Cyclic AMP analogues
  • Protein kinase C
  • Tryptophan hydroxylase

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