Full Answer Section

Dopamine (Precursor: Tyrosine):

1. Hydroxylation: The enzyme Tyrosine hydroxylase converts Tyrosine to L-DOPA (L-3,4-dihydroxyphenylalanine) in the presence of a cofactor and oxygen.
2. Decarboxylation: The enzyme DOPA decarboxylase removes a carboxyl group from L-DOPA, forming Dopamine.

Norepinephrine (Precursor: Tyrosine):

1. Hydroxylation: Same as Dopamine step 1, Tyrosine hydroxylase converts Tyrosine to L-DOPA.
2. N-methylation: The enzyme Phenylethanolamine N-methyltransferase (PNMT) adds a methyl group to L-DOPA, forming Dopamine.
3. Oxidation: The enzyme Dopamine beta-hydroxylase converts Dopamine to Norepinephrine in the presence of oxygen and a cofactor.

Key Points:

• Both Dopamine and Norepinephrine utilize Tyrosine as a precursor, but their pathways diverge after the initial hydroxylation step.
• Serotonin synthesis doesn’t involve methylation, unlike Dopamine and Norepinephrine.