Possible Interaction: Tryptophan and Vitamin B 6

“ PLP also serves as a coenzyme in the catabolism of tryptophan.”

“We believe that the metabolic alteration of tryptophan is secondary to a deficit of pyridoxal phosphate and nicotinamide-dependent enzyme activities.”

“6 Tryptophan loading was followed by an abnormally large increase in the excretion of these and other metabolites, which could be partially blocked by the simultaneous administration of pyridoxine , suggesting that there may be a functional deficiency of pyridoxine.”

“Since pyridoxine is required for orderly catabolism of tryptophan and pyridoxine corrected this metabolic aberration, it is not unreasonable to state that in hyperthyroidism, the availability of pyridoxine is limited.”

“However, these two infants, like the control infants, required only 0.3 to 0.4 mg of vitamin B6 daily to prevent excretion of xanthurenic acid after receiving a dose of tryptophan.”

“Thus, both tryptophan and pyridoxine possess antihypertensive properties, and the combination of the two appeared to provide greater protection than either alone.”

“Larger decreases in the catabolism of tryptophan were seen after pyridoxine deprivation.”

“It is suggested that this increase in the uptake of tryptophan into the brain following a relatively large dose of vitamin B6 may explain the beneficial action of the vitamin in some cases of depressive illness.”

“It appeared that a high dose of tryptophan in B-6-deficient rats could cause a greater deficiency of pyridoxal 5-phosphate.”

“Steady-state fluorescence spectra gave tryptophan emission of the apoenzyme that is 3.3-fold higher than the emission of either the native or reconstituted enzyme, suggesting that PLP is a potent quencher of tryptophan emission.”