Division of Chemistry and Toxicology
	Phenylketonoria Unit

		Phenylalanine is an essential amino acid which is converted to tyrosine by the liver enzyme phenylalanine hydroxylase. When this enzyme is decreased or absent, (as in Classical PKU), phenylalanine or its metabolites begin to elevate in the blood. Phenylketonuria is a hereditary autosomal recessive disorder characterized by mental retardation, convulsions, skin abnormalities, and behavioral disturbances. Screening for elevated levels of phenylalanine in newborns is important for early diagnosis and treatment of this disorder.

 

	Principles of the Test
		This procedure manufactured by Perkin Elmer Wallac, Inc. is a modification of the fluorometric procedure published by McCamman and Robins in 1962. The assay is based on the enhancement of the fluorescence of a phenylalanine-ninhydrin reaction product by the dieptide, L-leucyl-L-alanine.  A succinate buffer is used to optimize the fluorescence and increase specificity.  The copper reagent is used to further enhance the reaction and reduce background.  This method measures phenylalanine quantitatively in the presence of other amino acids. Eleanor Stanley, MT(ASCP), Unit Manager 517-335-9599 stanleye@state.mi.us