Tryptophan presentation metabolism Mbbs RUD

Tryptophan metabolism

1. Tryptophan Metabolism
11.Dec.16

2. Tryptophan
-It’s an essential amino acid that is made from plant or animal
sources.
-Tryptophan is important to the functions of many organs in the body.
-Tryptophan is essential for the production of the B vitamin, niacin.
-It is used by the brain to produce serotonin, a necessary
neurotransmitter that transfers nerve impulses from one cell to
another. Consequently, tryptophan helps to depression and insomnia
and to stabilize moods

3. Metabolic Pathways
1-Serotonin pathway.(1-3 %)
2-kynurenine pathway.(90 %)
3-Protein synthesis.
4-Bacterial degradation. (4-6 %)
-Approximately 0.5% of ingested tryptophan is excreted unchanged in
urine.

4. 1-Serotonin Pathway
-Serotonin is one of the most important signaling molecules
within the Gut, where it plays a pivotal role in initiating secretory and
motor reflexes.
Tryptophan(Tryptophan hydroxylase )→ 5-hydroxytryptophan(AADC)→ Serotonin
-Serotonin is produced by thr GIT Enterochromaffin cells &
stored in a large dense core vesicles and synaptic-like
microvesicles.

5. -Carcinoid Syndrome , It’s characterized by flushing, diarrhoea,
cramps, skin abnormalities, asthmatic wheezing and valvular heart
disease associated with elevated 5-HT levels , Due to the deficiency
of AADC (Aromatic amino acid decarboxylase).
-Melatoninhas important effects in Circadian rhythms , sleep-
wake cycles and other phenomena showing circadian rhythm.
Consequently, it has been reported to have significant effects
on reproduction for some Animals.
-Serotonin (serotonin N-acetyltransferase)→ N-acetylserotonin (Methylation)→ Melatonin

6. 2-Kynurenine Pathway
-Important in Clearance of excess tryptophan & Regulation of plasma
tryptophan levels.
-Provides :
●Quinolinic acid -> immunoregulatory processes.
●Nicotinamide & Nicotinic acid -> precursors for niacin ( Vit. B3)
●Picolinic acid -> chelating agent.

7. 3-Protein synthesis,Tryptophan is a rate-limiting
amino acid in protein synthesis Due of its limited availability in
food.
4-Bacterial Degradation :
-Approximately 4–6% of tryptophan undergoes bacterial
degradation yielding indole, indican, and indole acid
derivates.
-The main bacterial breakdown product of tryptophan is
indole.