Metabolism of catecholamines
Metabolism of catecholamines
Monoamine Oxidase (MAO)
- Concentrated in the liver and kidney, but otherwise present all over the body
- Present mainly in the outer mitochondrial surface
- Present in sympathetic nerve terminals, and metabolizes released neurotransmitter
- Deaminates catecholamines, BUT…
- They have to have an amine group without too large a substituent, AND
- They cannot have a substituent at the alpha carbon (like, say amphetamine does)
MAO-A
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- Peripherally, located in the syncytiotrophoblast of the term placenta, and in the liver
- Centrally, found in noradrenegeric neurons, mainly locus coeruleus
MAO-B
-
- Peripherally, located in the platelets, lymphocytes and the liver
- Centrally, found in serotonergic neurons
Catechol -O- methyltransferase (COMT)
-
- Concentrated in the liver and kidney, but otherwise present all over the body
- Present mainly in the cytoplasm
- THIS IS THE ENZYME that metabolizes most of intravenously administered catecholamines
- Exchanges the hydroxyl group at the 3 position on the catechol ring for a methyl group, BUT…
- The catecholamine ring MUST be intact with 2 hydroxyl groups, otherwise it wont work
References
For this sort of really basic stuff, no matter where you look you will find essentially the same information.
I used chapters from "Goodman & Gilman's The Pharmacological Basis of Therapeutics" 11th ed by Brunton et al, and "Basic & Clinical Pharmacology" 11th ed. By Katzung et al.
I also perused Peck and Hill "Pharmacology for Anaesthesia and Intensive care" as well as the notoriously error-prone "Handbook of Pharmacology and Physiology in Anaesthetic Practice" by Stoelting and Hillier. Neither covered this subject in a depth I found satisfying.
Goodman and Gilman's remains a canonical text.