Activation of brain tryptophan hydroxylase by ATP-MG2+: dependence on calmodulin.
Proceedings of the National Academy of SciencesPublished 1 August 1980Open access
Donald M. Kuhn, J P O'Callaghan, Judith C. Juskevich, Walter Lovenberg
Citations76
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TL;DR
Results indicate that the activation of tryptophan hydroxylase by phosphorylating conditions is dependent on both calcium and calmodulin.
Abstract
Tryptophan hydroxylase [tryptophan 5-monooxygenase, L-tryptophan,tetrahydropterin:oxygen oxidoreductase (5-hydroxylating), EC 1.14.16.4] is activated by phosphorylating conditions (ATP-Mg2+) in a calcium-dependent, cyclic AMP-independent manner. Addition to the phosphorylation reaction of certain antipsychotic drugs that bind to calmodulin, the heat-stable calcium-binding protein, prevents the activation of tryptophan hydroxylase by ATP-Mg2+ in a concentration-dependent fashion. External addition of purified calmodulin protects the enzyme from the drug-induced effects. Calmodulin-free tryptophan hydroxylase prepared by affinity chromatography on fluphenazine-Sepharose is not activated by ATP-Mg2+ whereas addition of calmodulin to calmodulin-free enzyme restores the responsiveness of the hydroxylase to ATP-MG2+ only in the presence of Ca2+. These results indicate that the activation of tryptophan hydroxylase by phosphorylating conditions is dependent on both calcium and calmodulin.
Keywords
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