The use of deuterated phenylalanine for thein vivo assay of phenylalanine hydroxylase activity in children
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Fifteen children, five with phenylketonuria (PKU), five with hyperphenylalaninaemia, and five phenotypically normal but at risk of being carriers for PKU, were given [ring2H5]phenylalanine orally in amounts ranging from 75 mg/kg to 10 mg/kg. Plama was assayed for [2H5]phenylalanine and [2H4]tyrosine at hourly intervals, the amino acids being measured as theN-acetyl, n-propyl esters by gas chromatography-mass spectroscopy. The results obtained were calculated as the log of the ratio [2H5]phenylalanine: [2H4]tyrosine in the plasma. The five patients with PKU had ratios of infinity because no [2H4]tyrosine was measured in their plasma during the experimental period. The patients with hyperphenylalaninaemia had log ratios over 2.00 throughout the assay period. Among the five normal children three are considered to be carriers for PKU as the logarithms of the [2H5]phenylalanine: [2H4]tyrosine ratios were 1.77, 1.73, and 1.33 and remained over 1.00 during the assay period. The other children had log ratios of 1.16 and 1.00 at the first hour which dropped below 1.00 subsequently, suggesting normal activity of phenylalanine hydroxylase.
KeywordsEster Tyrosine Metabolic Disease Phenylalanine Experimental Period
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- Curtius, H.-Ch., Vollmin, J. A. and Baerlocher, K. The use of deuterated phenylalanine for the elucidation of the phenylalanine-tyrosine metabolism.Clin. Chim. Acta 37 (1972) 277–285Google Scholar
- Curtius, H.-Ch., Zagalak, M. J., Baerlocher, K., Schaul, J., Leimbacher, W. and Redweik, U.In vivo studies of phenylalanine-4-hydroxylase system in hyperphenylalaninemics and phenylketonurics.Helv. Paediatr. Acta 32 (1978) 461–469Google Scholar
- Danks, D. M., Bartholomé, K., Clayton, B. E., Curtius, H.-Ch., Grobe, H., Kaufman, S., Leaming, R., Pfliederer, W., Rembold, H. and Rey, R. Malignant hyperphenylalaninemia, current status.J. Inher. Metab. Dis. 1 (1978) 49–53Google Scholar
- Jervis, G. A. Phenylpyruvic oligophrenia, deficiency of phenylalanine oxidising system.Proc. Soc. Exp. Biol. Med. 82 (1953) 514–515Google Scholar
- Matthews, D. W., Ben Galim, E. and Bier, D. M. Determination of stable isotopic enrichment in individual plasma amino acids by chemical ionization mass spectrometry.Anal. Chem. 51 (1979) 80–84Google Scholar
- Tourian, A. Y. and Sidbury, J. B. Phenylketonuria. In Stanbury, J. B., Wyngaarden, J. B. and Fredrickson, D. S. (eds.)The Metabolic Basis of Inherited Disease, McGraw-Hill, New York, 1978, pp. 240–255Google Scholar
- Trefz, F. K., Erlenmaier, T., Hynneman, D. H., Bartholomé, K. and Lutz, P. Sensitivein vivo assay of phenylalanine hydroxylating system with a small intravenous dose of heptadeuteroL-phenylalanine using high pressure liquid chromatography/mass fragmentography.Clin. Chim. Acta 99 (1979) 211–220Google Scholar