ABSTRACT
Phenylalanine, which makes up over half of the aspartame molecule, is an essential component of body proteins and an important precursor of many aromatic compounds required for normal body function. The nutritional essentiality of aromatic amino acids for mammals had been recognized prior to 1930. Phenylketonuric subjects, rats given a loading dose of phenylalanine (Phe), and rats that have been injected with p-chlorophenylalanine to inhibit phenylalanine hydroxylase excrete products of the phenylalanine transamination pathway, phenylpyruvate and its reduction product phenyllactate. Chronic glucagon treatment increased the activity of Phe-pyruvate aminotransferase by 10 fold and increased the quantity of Phe degradation products, mainly phenylpyruvate, excreted in the urine by about 4 fold. Phenylalanine tolerance tests can be used to estimate the phenylalaninedegrading capacity of human subjects. Epinephrine and norepinephrine, besides being neurotransmitters, are hormones produced by the adrenal medulla which are released in response to neural stimuli.
