The metabolism of tyrosine and phenylalanine in premature infants: the effect of large doses

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Abstract
Premature infants on various dietary protein levels were fed L-tyrossine or L-phenylalanine with and without ascorbic acid. Their excretion of phenolic intermediate metabolites reached a peak value soon after feeding the amino acid, but fell to normal values within a few days. The effect of ascorbic acid was greatly to reduce the excretion of intermediate metabolites. A similar investigation of full-term infants is not yet complete, but there seems as much variation as in the premature infants, especially in response to ascorbic acid. By paper chromatography it was shown that the excretion of amino acids other than tyrosine (or phenylalanine where this was fed) was not affected by the test dose of the amino acid.