Abstract
It has been suggested that urinary p-hydroxyphenylpyruvate In Medes-type tyrosinosis may arise from renal deamination of tyrosine.
Two siblings with tyrosinosis were studied. The propositus has tyrosinemia (7-10 × normal), and prominant p-hydroxyphonyl-pyruvic aciduria. His sister has tyrosinemia (18 × normal) but urinary organic acids are less well characterized. Neither child has hepatic or renal disease or Richner-Hanhart Syndrome.
Both children and a control subject received L-15N tyrosine and D-15N tyrosine orally on separate occasions. Of the 15N excreted as ammonia and urea in 5 hrs after D-tyrosine, 43% and 63% were excreted as ammonia by the affected children, and 48% by the control. After L-tyrosine, 14% and 16% were excreted as ammonia by the tyrosinotic children, and 16% by the control. Since D-amino acids are metabolized only through oxidative deamination, these results show that oxidative deamination of amino acids can be expected to yield urinary ammonia. Failure to find increased 15N-NH3 in the urine of the affected children after L-15N-tyrosine indicates that oxidative deamination of L-tyrosine does not play a quantitatively significant role in the metabolism of tyrosine in these children. Furthermore, kinetic analysis of 15N excretion in these studies does not suggest any qualitative abnormality in the metabolism of the amino nitrogen of tyrosine in the affected children, indicating that their physiologic abnormality is failure of catabollsm of the carbon skeleton of tyrosine.
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Nicholson, J. TYROSINOSIS: METABOLISM OF 15N-TYROSINE. Pediatr Res 11, 461 (1977). https://doi.org/10.1203/00006450-197704000-00546
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DOI: https://doi.org/10.1203/00006450-197704000-00546
