A DEFECT IN THE METABOLISM OF TYROSINE AND PHENYLALANINE IN PREMATURE INFANTS. I. IDENTIFICATION AND ASSAY OF INTERMEDIARY PRODUCTS 12

Abstract

An aberration in the metabolism of aromatic amino acids was demonstrated in premature infants who were fed relatively high protein diets (5 g. or more per kg. per day) in the form of cow''s milk without supplements of vit. C. This aberration was not spontaneously demonstrable in full term infants on comparable diets but it could be artificially provoked in them by the ingestion of the aromatic amino acids, d,l-phenylalanine and l-tyrosine. The defect consisted in an inability to decarboxylate aromatic amino acids beyond the organic acid stage and it was manifested by the appearance in urine of the intermediary products, p-hydroxyphenyllactic and p-hydroxyphenylpyruvic acids in large amts. Both these substances were isolated and their identity established by chemical and spectroscopic analysis. The defect, when present, could be promptly eradicated by the adm. of vit. C in adequate dosage and this effect was specific. A number of other agents thus far investigated including vits. A, D and the B complex, given singly and in combination, were ineffective in abolishing the defect. The aberration is probably an interrelated function of at least 3 factors: the maturity of the infant, the level of protein intake and the state of saturation of the tissues with vit. C. These observations provide a new approach for studying the intermediary metabolism of aromatic amino acids in the human organism and demonstrate a hitherto unrecognized function of vit. C in human nutrition.