Facts About Phenylalanine
L-phenylalanine is an essential amino acid which can be converted to L-tyrosine by a complex biochemical process which takes place in the liver. L-tyrosine can be converted by neurons in the brain to dopamine and neropinphrine (noradrenaline), hormones which are depleted by stress, overwork and certain drugs. By replenishing norepinephrine in the brain, mental energy levels are enhanced, some forms of depression are alleviated, and a feeling of satiety often occurs. Because of the liver conversion necessary for L-phenylalanine to have these effects, L-tyrosine if often faster acting. In addition, the conversion step from L-tyrosine to norepinephrine may be enhanced if the cofactors (vitamins B6 and C) are included.
Some of the norepinephrine will also be converted to epinephrine (adrenaline) in the brain's adrenal medulla by use of S-adenosylmenthionine (SAMe) as a methylaing agent. Since both norepinephrine and epinephrine can cause smooth muscle (arterial) contraction, care with blood pressure should be taken when supplementing L-phenylalanine or L-tyrosine. L-tyrosine is also a precursor of two thyroid hormones. D-phenylalanine is unique among amino acids because the D-form (normally not found in life) has biological activity, that is different from its L-stereoidomer. D-phenylalanine has been found to function as a pain reliever. D,L-phenylalanine is a 50/50 mixture of the two steroisomers.
Excerpt from Phenylalanine/Tyrosine
in The Directory of Life Extension Supplements, 2000, pg 43.