NITROGEN CONTAINONG COMPOUNDS
Catecholamines:
Catechol dopamine norepinephrine epinephrine
❖ Includes dopamine, norepinephrine, and epinephrine. They are all derived from AA
tyrosine and contain amine group.
❖ Dopamine and norepinephrine considered as neurotransmitters while epinephrine
considered as a hormone.
SYNTHESIS OF CATECHOLAMINES: They are produced by several successive reactions so that
each substance produced is the reactant for the reaction that follows. Starting with a tyrosine
AA that is hydroxylated by tyrosine hydroxylase enzyme producing the catechol ring (benzene
ring with tow hydroxyl group in tow adjacent carbons). Further reactions occur to the catechol
ring by adding ethylamine producing dopamine. Dopamine is hydroxylated on the ethylamine
sidechain producing norepinephrine. Finally, norepinephrine is methylated by methyl
transferase producing epinephrine.
DEGRADATION OF CATECHOLAMINES:
Catecholamines are degraded by to mechanisms:
1) Oxidative deamination catalyzed by monoamine oxidase (MAO)
2) O-methylation by Catechol-O-methyltransferase (COMT) using
SAM as the methyl donor. (MAO and COMT work in complementary
way to each other).
Further explanation: If we start degradation of Epinephrine by COMT
it we give us Metanephrine, after that MAO will work and give us VMA,
but if we start the degradation by MAO we will have Dihydoxymandelic
Acid as an intermediate, then COMT will give us VMA.
Notice from this example that if we start with different enzymes, we
will get different intermediates, but because of the complementary
Catecholamines:
Catechol dopamine norepinephrine epinephrine
❖ Includes dopamine, norepinephrine, and epinephrine. They are all derived from AA
tyrosine and contain amine group.
❖ Dopamine and norepinephrine considered as neurotransmitters while epinephrine
considered as a hormone.
SYNTHESIS OF CATECHOLAMINES: They are produced by several successive reactions so that
each substance produced is the reactant for the reaction that follows. Starting with a tyrosine
AA that is hydroxylated by tyrosine hydroxylase enzyme producing the catechol ring (benzene
ring with tow hydroxyl group in tow adjacent carbons). Further reactions occur to the catechol
ring by adding ethylamine producing dopamine. Dopamine is hydroxylated on the ethylamine
sidechain producing norepinephrine. Finally, norepinephrine is methylated by methyl
transferase producing epinephrine.
DEGRADATION OF CATECHOLAMINES:
Catecholamines are degraded by to mechanisms:
1) Oxidative deamination catalyzed by monoamine oxidase (MAO)
2) O-methylation by Catechol-O-methyltransferase (COMT) using
SAM as the methyl donor. (MAO and COMT work in complementary
way to each other).
Further explanation: If we start degradation of Epinephrine by COMT
it we give us Metanephrine, after that MAO will work and give us VMA,
but if we start the degradation by MAO we will have Dihydoxymandelic
Acid as an intermediate, then COMT will give us VMA.
Notice from this example that if we start with different enzymes, we
will get different intermediates, but because of the complementary
