In chronic kidney failure, there is impairment in the conversion of phenylalanine to tyrosine.
As a result, tyrosine and the tyrosine/phenylalanine ratio are reduced in plasma and many
tissues, and phenylalanine concentrations tend to be normal or slightly increased. Although
animal studies indicate that the kidney is not a major contributor to the conversion of
phenylalanine to tyrosine, human studies conducted in the postabsorptive state suggest that
the kidney plays a major role in the uptake of phenylalanine and its hydroxylation and …