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Heterozygote detection in two hype rphenylalaninemia types: classic phenylketonuria and dihydrobiopterin biosynthesis deficiency

Janice C. Dutra^{I, III}; Tania A. Weimer^II; Roberto Giugliani^{I, III}; Carlos A. Netto^III

^IUnidade de Genética Médica, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, 90000 Porto Alegre, RS, Brasil
^IIDepartamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, 90000 Porto Alegre, RS, Brasil. Send correspondence to T.A.W.
^IIIDepartamento de Bioquímica, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, 90000 Porto Alegre, RS, Brasil

ABSTRACT

Phenylalanine (P) and tyrosine (T) serum levels were determined fluorimetrically in normal controls (N = 41), as well as in obligate heterozygotes for two types of hyperphenylalaninemia (HP): classical phenylketonuria (HP I, N = 8), and dihydrobiopterin biosynthesis deficiency (HP V, N = 6). P and T values were 79.0 ± 15.8 and 86.6 ± 19.0 for controls; 158.5 ± 18.8 and 96.7 ± 25.7 for HP I, and 148.3 ± 28.8 and 85.5 ± 27.7 for HP V, respectively. The P²/T ratio and the discriminant function using simultaneously P and T were the best parameters to distinguish controls from both types of heterozygotes. But no discrimination could be obtained from HP I vs. HPV heterozygotes.

Keywords: heterozygote; rphenylalaninemia; phenylketonuria; dihydrobiopterin.

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