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110

 Functional Assessment of Urinary Neuro-biogenic Amines—A COMPREHENSIVE GUIDE

intracellular oxidative stress. TH en-

zyme function may be down-regulated

by oxidative stress, nitrosative stress and

thiolation (reactions with sulfur amino

acids). Single nucleotide polymorphisms

(SNPs) in the genes coding for tyrosine

hydroxylase have been associated with

altered stress responses, blood pressure,

heart rate and norepinephrine secretion.

Evidence that TH polymorphisms con-

tribute to neuropsychiatric disorders re-

mains contradictory.

Levels of Tyrosine in the brain may

be influenced by the plasma levels of

other amino acids, as several amino ac-

ids may compete for a single transport-

er across the blood brain barrier (BBB).

Brain tyrosine levels control the rate of

synthesis for the catecholamine neu-

rotransmitters in the central nervous

system (CNS). Tyrosine is metabolized

to glutamate by tyrosine aminotransfer-

ase (TAT), primarily in the liver.

Receptors:

There are no known receptors for the

amino acid tyrosine.

Consider:

Phenylalanine precursor status

( Amino Acids, Comprehensive Stool Analysis )

Selenium status

( RBC Elements )

Glutathione status

( Glutathione; erythrocytes )

Oxidative stress

( DNA Oxidative Damage Assay/8-OHdG )

References:

Cansev, M.; Wurtman, R.J. (2007) Chapter 4

Aromatic Amino Acids in the Brain

Handbook of Neurochemistry and Molecular

Neurobiology

Springer US

Fernstrom, John D (2000)

Can nutrient supplements modify brain

function?

Am J Clin Nutr

vol. 71 (6) p. 1669S-1673

Fernstrom, John D.; Fernstrom, Madelyn H.

(2007)

Tyrosine, Phenylalanine, and Catecholamine

Synthesis and Function in the Brain

J. Nutr.

vol. 137 (6) p. 1539S-1547

Leyton, M; Young, SN; Pihl, RO; Etezadi, S;

Lauze, C et al. (2000)

Effects on Mood of Acute Phenylalanine/

Tyrosine Depletion in Healthy Women

American College of

Neuropsychopharmacology

vol. 22 (1) p.

52-63

Matthews, Dwight E. (2007)

An Overview of Phenylalanine and Tyrosine

Kinetics in Humans

J. Nutr.

vol. 137 (6) p. 1549S-1555

Rao, Fangwen; Zhang, Lian; Wessel, Jennifer;

Zhang, Kuixing; Wen, Gen et al. (2007)

Tyrosine Hydroxylase, the Rate-Limiting

Enzyme in Catecholamine Biosynthesis:

Discovery of Common Human Genetic

Variants Governing Transcription,

Autonomic Activity, and Blood Pressure

In Vivo

Circulation

vol. 116 (9) p. 993-1006

Zhang, Lian; Rao, Fangwen; Wessel, Jennifer;

Kennedy, Brian P.; Rana, Brinda K. et al.

(2004)

Functional allelic heterogeneity and pleiotro-

py of a repeat polymorphism in tyrosine

hydroxylase: prediction of catechol-

amines and response to stress in twins

Physiol Genomics

vol. 19 (3) p. 277-291