Urine 4-hydroxyphenylpyruvic acid

TyrasinBtnia (neonatal tyrcsinetnial Insufficient levels of the enzyme hydroxyphenylpyruvic acid oxidase or tyrosine transaminase. Trsnsjent condhion of newtnms inixeased levels of tyrosine in blood arxl urite ttop as iriam matures not assodaled wnh specific symtoms. Tyrosine in blind and urine returns to normal as infant matures. Vitamin C helps reduce blood levels. Reduced protein intake beneficial oiieti occurs in premature babies. 

An example of a transient deficit that is the result of an immature enzyme system is a disorder in which the identification of increased concentrations of tyrosine and 4-hydroxyphenylpyruvic acid (4-HPPA) in urine of a premature newborn would suggest reduced activity of 4-HPPA oxidase. Administration of pharmacological doses of ascorbic acid, the cofactor required for activity of this enzyme, may overcome the temporary oxidase deficit and stimulate catabolism of the accumulating 4-HPPA. Figure 4 is an illustration of this disorder, which is termed transient neonatal tyrosinaemia. 

Figure 4 The urinary organic acids excreted by a premature infant with immature 4-hydroxyphenylpyruvic acid oxidase. This disorder, aiso known as transient neonatai tyrosinaemia, is characterized by excretion of elevated amounts of 4-hydroxyphenylacetic, 4-hydroxyphenyiiactic and 4-hydroxyphenyipyruvic acids. The urine was pretreated with hydroxylamine hydrochloride, which converts the keto acids into the respective oximes.

Additional errors of phenylalanine and tyrosine metabolism include tyrosinosis, or hereditary tyrosinemia, neonatal tyrosinemia, and alcaptonuria. In the first case, there is a probable defect in p-hydroxyphenylpyruvate oxidase. In neonatal tyrosinemia, the problem is transient and may be solved by the administration of ascorbic acid. Ascorbic acid is apparently a cofactor for p-hydroxy-phenylpyruvate oxidase. Alcaptonuria is a benign disorder in which homogen-tisic acid oxidase is inoperative and homogentisic acid is excreted in the urine. Air oxidizes the homogentisic acid to a pigment, giving urine a black color. This pigment also accumulates in the patient s tissues. 

Experimental alkaptonuria has also been produced in rats on a diet de-ficent in sulfur-containing amino acids (295). Similar excretory patterns were produced after additional phenylalanine, tyrosine, or their corresponding keto acids, and the condition was relieved on gi dng cysteine, but not ascorbic acid (644). Moreover the p-hydroxyphenylpyruvate excretion was much lower, relative to the homogentisic acid excretion, than in the type of ascorbate-dependent alkaptonuria studied by Sealock in the guinea pig (rats cannot in any case be made ascorbic acid-deficient). Xeuberger and Webster (644) also showed that this second type of experimental alkaptonuria could be produced in many types of amino acid imbalance, or in protein deficiency, and that the threshold intake of phenylalanine or tyrosine required to produce the condition varied with the nutritional state and also with the acid-base balance, acid urines being associated with a decreased homogentisic acid excretion (cf. also 150, 273, 787). 

Fates of tyrosine. Tyrosine can be degraded by oxidative processes to ace-toacetate and fumarate which enter the energy generating pathways of the citric acid cycle to produce ATP as indicated in Figure 38-2. Tyrosine can be further metabolized to produce various neurotransmitters such as dopamine, epinephrine, and norepinephrine. Hydroxylation of tyrosine by tyrosine hydroxylase produces dihydroxyphenylalanine (DORA). This enzyme, like phenylalanine hydroxylase, requires molecular oxygen and telrahydrobiopterin. As is the case for phenylalanine hydroxylase, the tyrosine hydroxylase reaction is sensitive to perturbations in dihydropteridine reductase or the biopterin synthesis pathway, anyone of which could lead to interruption of tyrosine hydroxylation, an increase in tyrosine levels, and an increase in transamination of tyrosine to form its cognate a-keto acid, para-hydroxyphenylpyruvate, which also would appear in urine as a contributor to phenylketonuria. 

In an infant with a serum phenylalanine concentration greater than 4 mg dl, the following have been recommended administration of 100 mg of ascorbic add 24 h prior to obtaining a repeat blood specimen, measurement of phenylalanine and tyrosine in blood, and evaluation of urine for the presence of phenylalanine, O-hydroxyphenylacetic acid, and phenylpyruvic acid, as well as tyrosine and tyrosine derivatives (p-hydroxyphenyllactic acid and p-hydroxyphenylpyruvic add) by chromatography and spot tests. Most infants will be found to have a transient defect that demands a new testing. 

Fig. 10.3 Chromatogram of organic acids extracted from the urine of an untreated patient with branched-chain keto aciduria (maple syrup urine disease), extracted and separated as described in the legend to Fig. 10.2. The chromatogram illustrates the overlapping peaks in the regions occupied by 3-hydroxybutyric, 2-hydroxyisovaleric and 2-oxoisovaleric acids (peak 1) and 2-oxo-3-methyl-valeric, 2-hydroxyisocaprioic and 2-oxoisocaproic acids (peak 2) and phosphate (peak 3). Other peaks of interest are (4) citric, (5) 4-hydroxyphenyl-lactic, (6) 4-hydroxyphenylpyruvic, (7) n-tetracosane (standard) and (8) -hexacosane (standard). (Compare with Fig. 10.4.)...

Fig. 10.4 Chromatogram of organic acids extracted from the same urine of the patient illustrated in Fig. 10.3, separated as their O-n-butyloxime and trimethylsilyl derivatives under the conditions described in the legend to Fig. 10.2. Peak identifications are 1, lactate 2, glycollate 3, unidentified 4, 2-hydroxy-n-butyrate plus 3-hydroxy-propionate 5, sulphate 6, 3-hydroxybutyrate and 3-hydroxyisobutyrate 7, 2-hydroxyisovalerate 8, 3-hydroxyisovalerate 10, 2-hydroxyisocaproate 11,2-hydroxy-3-methyl-n-valerate 12, phosphate 13,2-oxoisovalerate (peak 1) 14,2-oxoisovalerate (peak 2) 15, 2-oxo-3-methyl-/i-valerate (peak 1) 16, 2-oxo-3-methyl-n-valerate (peak 2) 17, 2-oxoisocaproate 18, citrate 19, 4-hydroxyphenyl-lactate 20, n-tetracosane (standard) 21, n-hexacosane (standard). The separation of O-n-butyloxime-TMS derivatives of the keto acids from the TMS-hydroxy acids and other components is apparent (compare with Fig. 10.3). Note the apparent loss of 4-hydroxyphenylpyruvate. (The horizontal axis represents the time elapsed in minutes from sample injection.)...

Fig. 16.12 Chromatogram of organic acids extracted using DEAE-Sephadex from the urine of a patient with untreated classical phenylketonuria, separated as their ethoxime and trimethylsilyl derivatives on 10 per cent OV-101 on HP Chromosorb W (80-100 mesh) by temperature programming from 110°C to 285°C at 4°C min" with a 5 min initial isothermal delay. Peak identifications are 1, sulphate 2, benzoate 3, phosphate 5, mandelate 6, 2-hydroxyphenylacetate 7, phenyl-lactate 8, phenylpyruvate 9, hippurate 10, citrate 11, 4-hydroxyphenyl-lactate 12, 4-hydroxyphenylpyruvate 13, undecanedioate (internal standard) 14, urate 15, indole-3-lactate 16.5-hydroxyindole-3-acetate 17, n-tetracosane (standard) 18, -hexacosane (standard). The position of phenylacetate is arrowed (peak 4) but free phenylacetate has never been observed by the authors in the urine of untreated phenylketonuric patients. (From Chalmers, 1974).

The unusual sulphur containing amino acid, hawkinsin , and cis- and transA-hydroxycyclohexylacetic acid observed in an extensively reported patient with transient neonatal tyrosinaemia (Danks et al., 1975 Niederwieser et al., 1977) in whom a defect in 4-hydroxyphenylpyruvate oxidase (see below) had been postulated (Niederwieser et al., 1978) have not been observed in any other patients with tyrosyluria or tyrosinaemia. The origins of these metabolites and their quantitative significance remain questionable, but it is perhaps significant that Bindel et al. (1976) have found 4-hydroxycyclo-hexane-l-carboxylic acid in the urine of several children with suspected metabolic disorders and proposed a dietary source for the metabolite. A bacterial origin also appears possible. 

Fig. 16.14 Chromatogram of organic acids extracted using solvents from the urine of a patient with hereditary tyrosinaemia and separated as their methoxime and tri-methylsilyl derivatives on 3 per cent OV-17 using temperature programming from 80°C to 260°C at 4°C min Peak identifications are 1, urea plus phosphate 2, succinate 3, 2-methyl-3-hydroxybenzoate (internal standard) 4, 2-oxoglutarate 5, 4,6-dioxo-heptanoate (succinylacetone) 6, 4-hydroxyphenylacetate 7, aconitate 8, citrate 9, isocitrate 10, dihydroxyphenylpropionate 11, 4-hydroxyphenyl-lactate 12, 4-hydroxyphenylpyruvate 13, 3,5-dioxo-octanedioate (succinylacetoacetate). (Redrawn with modifications from Lindblad etal, 1977)...

---