Possible Interaction: Lysine and Ornithine

“In the presence of excessive lysine the availability of arginine is reduced and the formation of ornithine is decreased in the liver; urea synthesis is reduced, but orotic acid synthesis is increased, and orotic aciduria results as carbamyl phosphate is directed toward the pyrimidine pathway.”

“For the older patients, alternative treatments such as the use of oral lysine to increase renal losses of ornithine need to be investigated further (Peltola et al 2000).”

“ Serum ornithine was increased 10- to 15-fold and serum lysine was slightly decreased in the affected patients.”

“Because lysine can act as a competitive inhibitor of the conversion of arginine to ornithine and urea, an increased level of plasma lysine may therefore inhibit the urea cycle.”

“Arginine and ornithine inhibited the initial uptake of lysine.”

“There was a reversible inhibition of urea formation in the perfused rat liver caused by 2.25-27 mM lysine acting with a Ki of 10.8 mM in competition with ornithine.”

“Moreover, competition studies suggest that increased levels of ornithine can depress the concomitant lenticular accumulation of arginine and lysine.”

“This was inhibited by 7 mM ornithine and 7 mM lysine.”

“The exit of pre‐loaded lysine into the vascular bed was inhibited by L‐ornithine (2 mM) and L‐arginine (10 mM) when pulsed through the lumen during the wash‐out, while 2‐aminoisobutyric acid (AIB), L‐histidine, L‐citrulline and L‐cystine had no effect.”

“The uptake of lysine into the epithelium from the vascular bed was accelerated by L‐ornithine and slightly by L‐arginine when they were present in the lumen, while L‐leucine, L‐alanine, beta‐alanine, L‐proline, L‐citrulline, sarcosine, L‐histidine and AIB had no effect.”

“ Lysine inhibits the uptake of ornithine and vice versa.”