Phenylalanine and Tyrosine
Aminoacids Metabolism

Author: Gianpiero Pescarmona
Date: 07/10/2007

Description

Description

Phenylalanine is an essential, non polar, large α-amino acid.

The codons for L-phenylalanine are UUU and UUC.

Source

Phenylalanine is contained in most protein rich foods, but especially good sources are dairy products (curd, milk, cottage cheese), avocados, pulses and legumes (particularly peanuts and lima beans), nuts (pistachios, almonds), seeds (piyal seeds), leafy vegetables, whole grains, poultry, fish and other seafoods).

Metabolism

L-phenylalanine can be converted into L-tyrosine by Phenylalanine Hydroxylase (PAH)

Phenylalanine uses the same active transport channel as tryptophan to cross the blood-brain barrier, and, in large quantities, interferes with the production of serotonin.

Tyrosine is an aromatic amino acid that is found in large quantities in casein

L-tyrosine is converted into L-DOPA, which is further converted into dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline) (the latter three are known as the catecholamines).

In the first two reactions, L-Tyrosine is converted into L-DOPA by the enzyme tyrosine hydroxylase, using tetrahydrobiopterin (THB), O2, and ferrous iron (Fe2+) as cofactors.
L -DOPA is converted into dopamine by the enzyme aromatic L-amino acid decarboxylase, using pyridoxal phosphate (PLP).
The native dopamine is stored in vesicles and when an action potential occurs, it is secreted by presynaptic cell Once in the synapse, dopamine binds to and activates postsynaptic dopamine receptors (D1 - D5) and after it has performed its synaptic duties , it is taken up via reuptake back into the presynaptic cell and re-stored into vesicles.
Below there is dopamine degradation:

The two important enzymes are monoamine oxidase (MAO) and catechol-O-methyl transferase (COMT). Homovanillic acid (HVA) is the final product of the metabolic pathway excreted in the urine.

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Comments
2012-09-27T08:46:30 - Paolo Pescarmona

dopamine beta hydroxylase and gambling

Dopamine

Dopamine is a catecholamine synthesized in the body by neurons, whose metabolic pathway is rapresented here:

In the first two reactions, L-Tyrosine is converted into L-DOPA by the enzyme tyrosine hydroxylase, using tetrahydrobiopterin (THB), O2, and ferrous iron (Fe2+) as cofactors.
L -DOPA is converted into dopamine by the enzyme aromatic L-amino acid decarboxylase, using pyridoxal phosphate (PLP).
The native dopamine is stored in vesicles and when an action potential occurs, it is secreted by presynaptic cell . Once in the synapse, dopamine binds to and activates postsynaptic dopamine receptors (D1 - D5) and after it has performed its synaptic duties , it is taken up via reuptake back into the presynaptic cell and re-stored into vesicles.
Below there is dopamine degradation:

The two important enzymes are monoamine oxidase (MAO) and catechol-O-methyl transferase (COMT). Homovanillic acid (HVA) is the final product of the metabolic pathway excreted in the urine.
2009-07-07T08:42:07 - Gianpiero Pescarmona

Sigma 1-type opioid receptor (Sigma1R) (Sigma1-receptor) (hSigmaR1) (SIG-1R) (SR31747-binding protein) (SR-BP) (Aging-associated gene 8 protein)

A protein with high Trp and Phen, Low Tyr

1. FUNCTION: Functions in lipid transport from the endoplasmic reticulum and is involved in a wide array of cellular functions probably through regulation of the biogenesis of lipid microdomains at the plasma membrane. Involved in the regulation of different receptors it plays a role in BDNF signaling and EGF signaling. Also regulates ion channels like the potassium channel and could modulate neurotransmitter release. Plays a role in calcium signaling through modulation together with ANK2 of the ITP3R-dependent calcium efflux at the endoplasmic reticulum. Plays a role in several other cell functions including proliferation, survival and death. Originally identified for its ability to bind various psychoactive drugs it is involved in learning processes, memory and mood alteration.
2. SUBCELLULAR LOCATION: Nucleus inner membrane. Nucleus outer membrane. Endoplasmic reticulum membrane. Lipid droplet. Cell junction. Cell membrane. Cell projection, growth cone. Note=Targeted to lipid droplets, cholesterol and galactosylceramide-enriched domains of the endoplasmic reticulum. Enriched at cell-cell communication regions, growth cone and postsynaptic structures. Localization is modulated by ligand- binding.
3. ALTERNATIVE PRODUCTS: Event=Alternative splicing; Named isoforms=5; Name=1; IsoId=Q99720-1; Sequence=Displayed; Name=2; IsoId=Q99720-2; Sequence=VSP_021982; Name=3; Synonyms=Sigma-R1A; IsoId=Q99720-3; Sequence=VSP_021986; Name=4; IsoId=Q99720-4; Sequence=VSP_021984, VSP_021985; Name=5; IsoId=Q99720-5; Sequence=VSP_021981, VSP_021983; Note=No experimental confirmation available;
4. TISSUE SPECIFICITY: Widely expressed with higher expression in liver, colon, prostate, placenta, small intestine, heart and pancreas. Expressed in the retina by retinal pigment epithelial cells.
5. MISCELLANEOUS: Depletion of OPRS1 by RNAi inhibits growth and survival signaling cascades and induces cell death. The OSPR1 antagonist rimcazole produces the same effect.
6. SIMILARITY: Belongs to the ERG2 family.
7. WEB RESOURCE: Name=Wikipedia; Note=Sigma-1 receptor entry; URL=

Cell localization and function

Several studies demonstrated that both type-1 and –2 sigma receptors regulate Ca2+ efflux from the endoplasmic reticulum.

Cell localization (from The Sigma Receptor: Evolution of the Concept in Neuropsychopharmacology 2005

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