Phenylalanine is a precursor for the amino acid tyrosine, which is essential for making neurotransmitters (e.g. epinephrine, norepinephrine, dopamine) and thyroid hormone. Neurotransmitters are the chemicals that communicate between nerve cells in the brain. It can relieve pain, alleviate depression, and suppress the appetite. Low levels may indicate a stressful lifestyle, leading to memory loss, fatigue, and depression.
Phenylalanine is a large neutral amino acid necessary for normal growth and development and is required for protein synthesis in humans. Phenylalanine is metabolized into acetoacetic acid and fumaric acid via tyrosine. A tyrosine metabolite, DOPA, is converted into the neurotransmitters epinephrine and norepinephrine. A lack of these neurotransmitters is a causal factor in Parkinson disease and schizophrenia.
References:
-https://www.mayoclinic.org/diseases-conditions/phenylketonuria/symptoms-causes/syc-20376302
-https://www.sciencedirect.com/science/article/pii/S1096719213003363
-https://www.sciencedirect.com/science/article/pii/B9780123749277000066
Phenylalanine (Plasma)
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