Enzyme Conversion
Biosynthesis of Neurotransmitters from Tyrosine and Tryptophan
Dopamine Biosynthesis from Tyrosine
Tyrosine is an amino acid precursor for several key neurotransmitters, including dopamine. The biosynthesis of dopamine involves the following steps:
- Tyrosine Hydroxylation:
Enzyme: Tyrosine hydroxylase (TH)
Reaction: Tyrosine is hydroxylated to L-DOPA (L-3,4-dihydroxyphenylalanine).
Cofactors: Tetrahydrobiopterin (BH4), O2
Equation: Tyrosine + BH4 + O2 → L-DOPA + BH2 + H2O
Enzyme Conversion
- Decarboxylation of L-DOPA:
Enzyme: Aromatic L-amino acid decarboxylase (AADC), also known as DOPA decarboxylase
Reaction: L-DOPA is decarboxylated to dopamine.
Cofactors: Pyridoxal phosphate (vitamin B6)
Equation: L-DOPA → Dopamine + CO2
Norepinephrine Biosynthesis from Tyrosine
Norepinephrine is synthesized from dopamine through the following steps:
- Dopamine Hydroxylation:
Enzyme: Dopamine β-hydroxylase (DBH)
Reaction: Dopamine is hydroxylated to norepinephrine.
Cofactors: Ascorbate (vitamin C), O2, Cu2+
Equation: Dopamine + Ascorbate + O2 → Norepinephrine + Dehydroascorbate + H2O
Enzyme Conversion
Serotonin Biosynthesis from Tryptophan
Serotonin is synthesized from the amino acid tryptophan through these steps:
- Tryptophan Hydroxylation:
Enzyme: Tryptophan hydroxylase (TPH)
Reaction: Tryptophan is hydroxylated to 5-hydroxytryptophan (5-HTP).
Cofactors: Tetrahydrobiopterin (BH4), O2
Equation: Tryptophan + BH4 + O2 → 5-HTP + BH2 + H2O
- Decarboxylation of 5-HTP:
Enzyme: Aromatic L-amino acid decarboxylase (AADC)
Reaction: 5-HTP is decarboxylated to serotonin (5-hydroxytryptamine or 5-HT).
Cofactors: Pyridoxal phosphate (vitamin B6)
Equation: 5-HTP → Serotonin + CO2
Summary of Biosynthetic Pathways
Dopamine:
- Tyrosine → (Tyrosine hydroxylase) → L-DOPA
- L-DOPA → (Aromatic L-amino acid decarboxylase) → Dopamine
Norepinephrine:
- Dopamine → (Dopamine β-hydroxylase) → Norepinephrine
Serotonin:
- Tryptophan → (Tryptophan hydroxylase) → 5-HTP
- 5-HTP → (Aromatic L-amino acid decarboxylase) → Serotonin
Each of these steps involves specific enzymes and cofactors essential for the proper conversion of precursor amino acids into their respective neurotransmitters. Understanding these pathways is crucial for insights into various physiological and pathological processes in the nervous system.
Enzyme Conversion
Summary of Biosynthetic Pathways
Dopamine:
- Tyrosine → (Tyrosine hydroxylase) → L-DOPA
- L-DOPA → (Aromatic L-amino acid decarboxylase) → Dopamine
Norepinephrine:
- Dopamine → (Dopamine β-hydroxylase) → Norepinephrine
Serotonin:
- Tryptophan → (Tryptophan hydroxylase) → 5-HTP
- 5-HTP → (Aromatic L-amino acid decarboxylase) → Serotonin
Each of these steps involves specific enzymes and cofactors essential for the proper conversion of precursor amino acids into their respective neurotransmitters. Understanding these pathways is crucial for insights into various physiological and pathological processes in the nervous system. APA.