- Catecholamines are degraded primarily by Monoamine Oxidase (MAO) and Catechol-O-Methyltransferase (COMT) into inactive metabolites, which are excreted in urine.
Steps of Catecholamines Catabolism
-
MAO Pathway:
- MAO (located in neuronal mitochondria) oxidizes catecholamines into dihydroxyphenylglycol aldehyde.
- This is further converted into vanillylmandelic acid (VMA) for excretion.
-
COMT Pathway:
- COMT methylates catecholamines to form metanephrine and normetanephrine.
- These are eventually converted into VMA, which is excreted in urine.
End Metabolites in Urine
- Vanillylmandelic Acid (VMA) – Major metabolite of norepinephrine and epinephrine.
- Homovanillic Acid (HVA) – Major metabolite of dopamine.
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