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Tryptophan hydroxylase regulation. Drug-induced modifications that alter serotonin neuronal function
1Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, Michigan, USA. donald.kuhn@wayne.edu
Advances in Experimental Medicine and Biology
|March 18, 2000
Summary
Dopamine-derived quinones, not dopamine itself, inactivate tryptophan hydroxylase, the key enzyme for serotonin synthesis. This finding explains how certain drugs may reduce serotonin levels and damage serotonin neurons.
Area of Science:
- Neurochemistry
- Enzymology
- Pharmacology
Background:
- Tryptophan hydroxylase is the rate-limiting enzyme in serotonin biosynthesis.
- Drugs like methamphetamine, MDMA, and L-DOPA can impair tryptophan hydroxylase function and harm serotonin neurons.
Purpose of the Study:
- To investigate the role of dopamine in the drug-induced inhibition of tryptophan hydroxylase.
- To determine if dopamine directly affects tryptophan hydroxylase activity.
Main Methods:
- Enzyme activity assays were performed.
- Protein modification analysis was conducted.
- Redox cycling of quinoproteins was studied.
Main Results:
- Dopamine-derived quinones, not dopamine, were found to inactivate tryptophan hydroxylase.
- Tryptophan hydroxylase was converted into a redox-cycling quinoprotein.
- A novel posttranslational modification of tryptophan hydroxylase was identified.
Conclusions:
- Dopamine-derived quinones are responsible for the inactivation of tryptophan hydroxylase.
- This posttranslational modification may underlie drug-induced reductions in serotonin synthesis.
- The findings provide insights into the neurotoxic mechanisms of certain drugs.