Possible Interaction: Levodopa and Tyrosine

“Treating parkinsonian rats twice daily with levodopa induces many of the characteristic features of the human motor complication syndrome and further increases the serine and tyrosine phosphorylation of specific NMDA receptor subunits.”

“A striking overlap is observed in the tyrosine and l-dopa biosynthetic pathways suggesting a common disease mechanism associated with these 2 heterogeneous disorders that warrants further investigation.”

“ L-tyrosine plus ACh (60 microM) or (120 microM) significantly increased (P < 0.01) intracellular L-Dopa and NE versus control, versus L-tyrosine alone and versus ACh alone.”

“ L-tyrosine significantly increased (P < 0.01) L-Dopa and norepinephrine (NE) content of lymphocytes.”

“Since intracellular L-Dopa after L-tyrosine plus ACh increased 6-fold versus basal, 2-fold versus L-tyrosine alone and 3-fold versus ACh alone, it is concluded that ACh might regulate CA synthesis in lymphocytes through an activation of the rate limiting enzyme tyrosine hydroxylase.”

“ Tyrosine as well as tryptophan decrease significantly after treatment with L-dopa , thus showing a competitive action of L-dopa to other aromatic amino acids on human brain uptake.”

“The other aromatic amino acids, L-Phe and L-Trp, and the L-Tyr analogues DL-m-Tyr, L-diiodotyrosine and L-dopa , strongly inhibit the uptake of L-Tyr.”

“1000 mg/kg l-Dopa produced an even greater increase in the concentration of tyrosine and threonine in the liver as well as inducing a significant increase in hepatic-aspartic acid and serine.”

“Subcutaneous injections of 500 mg/kg l-Dopa daily for 8 days increased the concentrations of isoleucine, methionine, threonine and tyrosine.”

“On the other hand, there is evidence that L-dopa inhibits the absorption of L-phenylalanine and L-tyrosine in patients with Parkinson's disease3.”

“Abstract Intraperitoneal injections of L-dopa (100 and 200 mg/kg) decreased the concentrations of tryptophan, tyrosine and serotonin in rat brain.”

“The extracellular tyrosinase activity produced remarkably higher levels of l-DOPA , i.e. 2.44 mg mL−1 when the media was supplemented with 5 mg mL−1l-tyrosine.”

“Since Tpl is only synthesized under L-tyrosine-induced conditions, the addition of L-tyrosine to the medium is unavoidable when preparing cells (the enzyme source), but severely impedes the pure preparation of the final product L-DOPA.”