Serotonin, Dopamine, and Norepinephrine Synthesis Pathways

Common Precursor: Tyrosine

1. Serotonin Synthesis:

• Tyrosine Hydroxylase: Converts tyrosine to L-DOPA.
• Aromatic L-amino acid decarboxylase: Converts L-DOPA to dopamine.
• Dopamine β-hydroxylase: Converts dopamine to norepinephrine.
• Phenylethanolamine N-methyltransferase (PNMT):

Converts norepinephrine to epinephrine.

Diagram 1: Serotonin Synthesis

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diagram showing the conversion of tyrosine to serotonin via LDOPA and dopamine

Common Precursor: Tryptophan

2. Serotonin Synthesis:

• Tryptophan hydroxylase: Converts tryptophan to 5-hydroxytryptophan (5-HTP).
• Aromatic L-amino acid decarboxylase: Converts 5-HTP to serotonin.

Diagram 2: Serotonin Synthesis from Tryptophan

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diagram showing the conversion of tryptophan to serotonin via 5HTP

3. Dopamine and Norepinephrine Synthesis:

• Tyrosine hydroxylase: Converts tyrosine to L-DOPA.
• Aromatic L-amino acid decarboxylase: Converts L-DOPA to dopamine.
• Dopamine β-hydroxylase: Converts dopamine to norepinephrine.

Diagram 3: Dopamine and Norepinephrine Synthesis

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diagram showing the conversion of tyrosine to dopamine and norepinephrine

Note: While dopamine and norepinephrine can be synthesized from tyrosine, serotonin is primarily synthesized from tryptophan. However, it’s important to note that there are some minor pathways that can convert tyrosine to serotonin.