Question

For acetylcholine, for norepinephrine, and for epinephrine:

Explain the biochemistry of each one’s synthesis (though you do not need to know the names of the enzymes involved in its biosynthesis), explain where each is synthesized (in which cells), know the mechanisms and/or enzymes by which each is removed from the secretory site.

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Thank you!

Answer 1

Norepinephrine and epinephrine synthesis

L tyrosine —> dihydrophenylalanine by the enzyme tyrosine hydroxylase.

dihydrophenylalanine —> dopamine by the enzyme dopa decarboxylase

dopamine —> norepinephrine by the enzyme dopamine beta oxidase

norepinephrine —> epinephrine by phenylethanolamine N methyl transferase.

Both epinephrine and norepinephrine is synthesised in chromaffin cells of adrenal medulla and sympathetic ganglia.

both epinephrine and norepinephrine is removed from the site by the enzyme catechol o methyltransferase and monotone oxidase .

comt is present in axon terminals and cell body.

mao is present in outer membrane of mitochondria.

acetylcholine synthesis.

Acetyl coA + choline —> acetylcholine by the enzyme cholineacetyltransferase.

synthesis takes places in the cytoplasm of the nerve terminal.

acetylcholine is metabolised by acetylcholinesterase in synaptic cleft.