Essential
Histidine
Essential AA; precursor to histamine; roles in enzyme active sites
Isoleucine
Essential BCAA; energy metabolism; complements leucine/valine
Leucine
Essential BCAA; mTOR signaling; protein synthesis; cognitive load support
Lysine
Essential AA; limiting in many cereals; complements legumes
Methionine
Essential AA; precursor to SAMe via methylation cycle
Phenylalanine
Essential AA; precursor to tyrosine → catecholamines
Threonine
Essential AA; structural proteins; mucin production
Tryptophan
Serotonin/melatonin precursor; NAD+ pathway substrate; LAT1 transport dynamics
Valine
Essential BCAA; supports protein balance and neurotransmitter transport competition