Phenylalanine also competes with uptake of other aromatic amino acids. Tryptophan is an essential amino acid that is in protein and is used for other purposes, and should be in daytime formulas in addition to nighttime formula. It is a precursor to serotonin, a neurotransmitter. In some cases large amounts of tryptophan are obtained in the diet, and the level of night-time formula will need to be reduced. Consult your physician for signs of this condition.
Tyrosine is the precursor for dopamine, epinephrine, norepinephrine, thyroxines and melanin.
Proline is used in protein synthesis in general and in collagen synthesis, it can be hydroxylated at certain sites to provide for the final steps of manufacture of collagen. Serine is the skeleton source that is used in a variety of pathways, including the unfortunate overproduction of cysteine by the cystathionine beta synthase enzyme. Taurine is an essential amino acid of unusual structure. It is used in manufacture of bile salts and in other pathways. Interestingly, it is a metabolite of cysteine.