Possible Interaction: Phenylalanine and Threonine

“ Phenylalanine oxidation, estimated from the rate of 14CO2 released in expired air during isotope infusion, decreased (P < 0.05) as threonine intake increased from 0.05 to 0.15 g/(kg.d) and was low and constant for threonine intakes >0.15 g/(kg.d).”

“The present results suggest that Thr and Phe may have a specific regulatory role in the secretion of pancreatic digestive enzymes in chicks when administered simultaneously.”

“Reduction of the … of lysine, threonine and methionine from the generous levels characteristic of a diet containing 240 g protein from skim milk/kg, to the requirement … determined separately in the presence of the generous levels of all the other amino acids, resulted in a twofold increase in phenylalanine ….”

“—High circulating levels of phenylalanine caused depletions of threonine , valine, methionine, isoleucine, leucine, histidine, tryptophan, and tyrosine in immature and adult rat brains.”

“ Threonine was only partly effective against the more severe growth depression caused by 5% of dl -phenylalanine.”

“Amino acids of Group I (l-tryptophan, l-methionine, and l-norleucine) counteract the inhibition by l-lysine only, amino …-valine, l-isoleucine, and l-norvaline) counteract the inhibition by l-threonine only, and those of Group III l-phenylalanine , l-alanine, glycine, and … l-lysine and l-threonine.”