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Separate tolerance tests with aspartame at 34 mg/kg-day and phenylalanine at 19 mg/kg-day were compared. The results reveal that slight serum elevation of phenylalanine and tyrosine occurred in the two PKU and the normal healthy adolescents. It would appear that the phenylalanine in the sweetener aspartame is small enough to be of little clinical significance.
The metabolites of phenylalanine, phenylacetate, phenyllactate, phenylpyruvate and phenylethylamine, were measured in the urine of PKU patients. In general correlation was found between serum phenylalanine excretion of these metabolites. However, there were individual variations in the quantities and type of metabolites excreted that could not be explained by blood phenylalanine levels. In a PKU pregnancy large quantities of phenylalanine metabolites were found in urine despite a modest elevation of serum phenylalanine. Increase in the excretion of phenylalanine metabolites was found in patients who were considered to have good blood phenylalanine control. These preliminary studies indicate that the current practice of allowing a wide range of blood phenylalanine in the treatment of PKU may have to be reexamined. Since these metabolites are neurotoxic, they may afford a new parameter for the study of PKU not only regarding the prevention of mental retardation but also with regards to behavior and learning disabilities.
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The crystal structures of the first stable alpha-diol from the alpha-halogenopyruvamide series, 3-chloro-2, 2-dihydroxy-3-phenylpropanamide, C(9)H(10)ClNO(3), and three products [3-(4-chlorophenyl)-2-cyano-2,3-epoxypropanamide, C(10)H(7)ClN(2)O(2), 3-bromo-2-cyano-2-hydroxy-3-p-tolylpropanamide, C(11)H(11)BrN(2)O(2), 3-bromo-2-oxo-3-p-tolylpropanamide, C(10)H(10)BrNO(2)] obtained during the systematic synthesis of alpha-halogenopyruvamides are reported. The crystal structures are dominated by hydrogen bonds involving an amide group. The stability of the geminal diol could be ascribed to hydrogen bonds which involve both hydroxyl groups.
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Biochemical studies carried out in seven members of a family with five phenylketonuric subjects are described. The concentration of phenylalanine and the phenylalanine/tyrosine ratios in the blood, together with the values obtained from the L-phenylalanine loading tests, were the criteria used to establish the diagnosis. The results suggest that the non-consanguineous parents, the children and their maternal aunt are homozygous for classical phenylketonuria; the paternal grandmother, as expected, was found to be heterozygous for this metabolic disorder. The mother, diagnosed in the fifth month of her last pregnancy, was treated with a low phenylalanine diet until delivery. Nevertheless, the girl who was born from that pregnancy showed some symptoms resulting from "maternal phenylketonuria", being diagnosed as phenylketonuric at one week of age and treated with a low phenylalanine diet thereafter.
Clinical isolates of Neisseria gonorrhoeae are commonly subject to growth inhibition by phenylpyruvate or by L-phenylalanine. A blockade of tyrosine biosynthesis is indicated since inhibition is reversed by either L-tyrosine or 4-hydroxyphenylpyruvate. Phenylalanine-resistant (PheR) and phenylalanine-sensitive (PheS) isolates both have a single 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP) synthase that is partially inhibited by L-phenylalanine (80%). However, PheS and PheR isolates differ in that the ratio of phenylpyruvate aminotransferase to 4-hydroxyphenylpyruvate aminotransferase is distinctly greater in PheS isolates than in PheR isolates. A mechanism for growth inhibition is proposed in which phenylalanine exerts two interactive effects. (i) Phenylalanine decreases precursor flow to 4-hydroxyphenylpyruvate through its controlling effect upon DAHP synthase; and (ii) phenylalanine is largely transaminated to phenylpyruvate, which saturates both aminotransferases, preventing transamination of an already limited supply of 4-hydroxyphenylpyruvate to L-tyrosine.
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