[Excretion of transamination products in hyperphenylalaninemia (author's transl)]

A low-phenylalanine diet was given for a period of three weeks to four untreated adult phenylketonurics with mental deficiency. One week before the diet was started, in the course of the diet and one week after its termination, some transamination products of phenylalanine, tryptophan and histidine were determined quantitatively. Each of the transamination products showed a positive correlation to the serum phenylalanine levels of the patients, probably due to the large affinity of 4-hydroxyphenylpyruvic acid and phenylpyruvic acid for the amino groups of the aromatic amino acids. This may also explain the low levels of epinephrine, norepinephrine and serotonine which has been observed by other authors in untreated phenylketonurics. Accordingly, treated phenylketonurics should suffer from a chronic deficiency of biogenic amines after termination of the low-phenylalanine diet.