Possible Interaction: Methionine and Tryptophan

“Notably, methionine 385 of IDO-2 was identified to interfere with the entrance of l-tryptophan to the active site of the enzyme, which explains the selectivity of the inhibitors.”

“Marked alterations in behavior in some patients were associated with the administration of l-methionine and of l-tryptophan.”

“The substitution of methionine with tryptophan or serine resulted in a decrease in the neotropic activity.”

“In the everted sac method, high concentrations of L-tryptophan or L-methionyl-L-tryptophan caused anomalous inhibition of absorption of L-tryptophan and L-methionine.”

“The formation of these alterations may be prevented by combined administration of nicotinamide + L-methionine or DL-tryptophan + L-methionine.”

“Tryptophan probably acts by a mechanism different from the osmoreceptor since slowing of gastric emptying by tryptophan was inhibited by methionine which has no effect on a stimulant of the osmoreceptor mechanism.”

“A natural competition may exist between methionine and tryptophan for vitamin B 6 which is utilized in the metabolic pathways of both amino acids.”

“As a working hypothesis, it is suggested that excess methionine may favor the channeling of tryptophan metabolism into indoleacetic acid production by inhibiting the nicotinic acid pathway or stimulating those pathways leading to formation of indoleacetic acid.”

“The addition of excess methionine to low tryptophan rations containing 6-methyl tryptophan resulted in a more marked protection against Lansing infection in mice than when the same amounts of methionine or 6-methyl tryptophan were fed alone.”

“The only complete co-elution is between tryptophan and methionine.”