Improved identification of heterozygotes for phenylketonuria using blood neopterin and biopterin

Abstract

A novel approach that combines information provided by the metabolism of pteridines and that of phenylalanine has been applied to the detection of heterozygotes for phenylketonuria. Phenylalanine, tyrosine, biopterin and neopterin have been measured in serum from normal controls and heterozygotes for classical phenylketonuria, before and after a phenylalanine oral load. Significant differences in neopterin and biopterin mean values in fasting serum and in the mean increase of biopterin induced by the phenylalanine load were found between groups. Inclusion of pteridine data in the discriminant analysis significantly improved the resolution of the classical phenylalanine loading test for the detection of heterozygotes for phenylketonuria.

Phenylalanine and Tyrosine Metabolism Analysis in Heterozygotes for Phenylketonuria and in Healthy Individuals

“…These findings are in agreement with previous studies. 23 The levels of Phe progressively increased and reached the highest peak at 30 minutes after overload administration, suggesting that Phe is being rapidly metabolized into Tyr. Statistical differences for Tyr levels were detected after T30, corroborating the metabolization of Phe into Tyr.…”