Related Experiment Videos
Dopamine formation from tyramine by CYP2D6
1Department of Chemical Biology, Osaka City University Medical School, Japan.
Biochemical and Biophysical Research Communications
|September 10, 1998
Summary
The enzyme cytochrome P450 2D6 (CYP2D6) converts trace amine tyramine into dopamine. This pathway contributes to dopamine formation from both internal and external tyramine sources.
Area of Science:
- Biochemistry
- Pharmacology
- Enzymology
Background:
- Dopamine is primarily synthesized from L-tyrosine via tyrosine hydroxylase and aromatic L-amino acid decarboxylase.
- Hepatic microsomes can form catecholamines, including dopamine, from trace amines like tyramine.
- The specific enzymes and pathways involved in tyramine-to-dopamine conversion require further elucidation.
Purpose of the Study:
- To investigate the formation of dopamine from trace amines using human hepatic microsomes and human cytochrome P450 (CYP) isoforms.
- To identify the specific CYP isoform responsible for converting tyramine to dopamine.
- To characterize the kinetic properties of this conversion process.
Main Methods:
- Utilized human hepatic microsomes and yeast-expressed human CYP isoforms for in vitro studies.
- Assayed the conversion of p-tyramine and m-tyramine to dopamine.
- Employed enzyme inhibition studies using bufuralol and anti-CYP2D1 antiserum.
- Determined kinetic parameters (Km values) for CYP2D6-mediated tyramine hydroxylation.
Main Results:
- CYP2D6 was identified as the sole human CYP isoform capable of efficiently converting p-tyramine and m-tyramine to dopamine.
- The hydroxylation of tyramine to dopamine in human hepatic microsomes was inhibited by CYP2D isoform-specific inhibitors and antiserum.
- Kinetic analysis revealed specific Km values for CYP2D6 with p-tyramine (190.1 ± 19.5 μM) and m-tyramine (58.2 ± 13.8 μM).
Conclusions:
- This study provides the first evidence that CYP2D6 can convert tyramine into dopamine.
- The findings suggest that dopamine can be synthesized from both endogenous and exogenous tyramine through CYP2D6-mediated hydroxylation.
- This alternative pathway for dopamine formation has implications for understanding dopamine homeostasis and the metabolism of tyramine-containing foods and drugs.