Synthesis

Metabolism-

L-Tyrosine

L-Dopa

L-Dopamine

Norepinephrine

Epinephrine

M etanephrine

FIGURE 32-7

Synthesis and metabolism of catecholamines. Arrows indicate molecular conversions catalyzed by specific enzymes. Bold arrows indicate major (preferred) pathways.

Enzymes: (1) tyrosine hydroxylase; (2) aromatic L-amino acid decarboxylase; (3) dopamine-jSymonooxygenase; (4) PNMT; (5) cateckel-o-methyltransferase; (

6

) monoamine

oxidase.