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PubMed1992

A synopsis of the unconjugated acidic transamination metabolites of phenylalanine in phenylketonuria.

We present blood and urine levels of unconjugated o-hydroxyphenylacetic, phenyllactic and phenylpyruvic acids in 61 children (2 years of age and above) and juveniles with phenylketonuria on or partially off diet. The samples were obtained during 185 scheduled outpatient visits and have been analysed with gas chromatographic methods. The compiled data define reference ranges of phenylalanine transamination capacity and of renal transport of metabolites which may be of value in further studies on the pathogenesis of phenylketonuria.

Adolescent↗
PubMed1975

Studies on the experimental phenylketonuria in rats.

Wister albino pregnant rats were fed on pellets containing 3.5% L-phenylalanine (Phe) from 10 days before the expected date of birth. The diet was then switched to 7% Phe pellets at the third week after birth. Baby rats were reared with breast milk, and weaned at the end of the 4th week after birth; thereafter, they were reared with a normal diet for one week at the 5th week, and then were given 7% Phe diet from the 6th week. These rats, which were reared with a diet of high Phe, showed a similar metabolic pattern to that of human phenylketonuria (PKU) in the following aspects: definite suppression of the liver Phe hydroxylase activity, excretion of a large amount of phenylpyruvic acid (PPA) and phenyllactic acid (PLA) into urine, and an elvated level of blood Phe content. But, they had an excessive amount of blood tyrosine (Tyr), and concurrently excreted massive homogentisic acid (HGA) in urine just as in human tyrosinemia alkaptonuria. The absence of urinary o-hydroxyphenylacetic acid (o-HPAA) was also a distinct difference from human PKU. In some rats, mild inhibition of the liver Phe hydroxylase activity was observed. In other rats, there was no excretion of PPA into urine as in human hyperphenylalaninemia. Further, the regulatory mechanism of Phe catabolism of experimental PKU was discussed by analysing the enzyme activity of the liver Phe hydroxylase, phenylalanine-pyruvate (Phe-Pyr) transaminase and tyrosine alpha-ketoglutarate (Tyr-alpha-Kg) transaminase at different developmental stages of the rats.

Amino Acids↗
PubMed1980

Absence of a significant renal threshold for two aromatic acids in phenylketonuric children over two years of age.

There is a steady and nonlinear relationship between the levels of both phenylpyruvic acid (PPA) and o-hydroxyphenylacetic acid (oOPAA) in urine and the plasma levels of phenylalanine (phe) in children more than two years of age with phenylketonuria (PKU). If phe levels in blood rise above 0.35 mM (5.8 mg/100 ml) both aromatic acids are found regularly in urine. Typically, urinary concentrations of PPA are about 5 times higher than those of oOPAA. This report is based on the analysis of 94 samples from 51 children, on or off diet.

Adolescent↗
PubMed2004

A molecularly imprinted polymer-based synthetic transaminase.

The design, synthesis, and evaluation of a molecularly imprinted polymer transaminase mimic is described. Methacrylic acid-ethylene glycol dimethacrylate copolymers were synthesized using, as a template, a transition state analogue (TSA) for the reaction of phenylpyruvic acid and pyridoxamine to yield phenylalanine and pyridoxal. Polymer suitability was established on the basis of (1)H NMR studies of template-functional monomer interactions. Polymer recognition characteristics were examined in a series of HPLC studies using the polymers as chromatographic stationary phases. Selectivity for the TSA, relative to substrates and products, was observed in both aqueous and nonpolar media. In the latter case (chloroform/AcOH, 96:4), an enantioseparation factor (alpha) of 2.1 was obtained, and frontal chromatographic studies revealed the presence of 11.9 +/- 0.2 micromol g(-1) (dry weight) of enantioselective sites. Polymers imprinted with the l-form of the oxazine-based TSA induced a 15-fold enhancement of the apparent reaction rate (app. V(max) 2.5 x 10(-7) mol s(-1); app. K(m) 8.2 x 10(-3) M) and enantioselective production of phenylalanine (32 +/- 4% ee) for reactions conducted in an aqueous buffer system. Substrate selectivity was evident, and a turnover number (k(cat)) of 0.1 s(-)(1) was determined. This is the first example of the catalysis of sigmatropic shifts in aqueous media by molecularly imprinted polymers.

Biomimetic Materials↗
PubMed1999

Reversal of optical induction in transamination by regioisomeric bifunctionalized cyclodextrins.

Two isomeric compounds have been synthesized carrying a pyridoxamine on C-6 of beta-cyclodextrin and an imidazole unit on C-6 of the neighboring glucose residue. Each one stereoselectively transaminates phenylpyruvic acid to produce phenylalanine, and with opposite stereochemical preferences. Structure determinations by X-ray crystallography and NMR spectroscopy indicate that the imidazole units serve to block proton addition from their side, rather than acting to protonate the transamination intermediates. Related cyclodextrin-pyridoxamine compounds had been reported carrying ethylenediamine units instead of imidazoles, and high enantioselectivities in transamination were claimed. Our work indicates that these claims are incorrect, and that only poor selectivities are seen that are often unrelated to the position of the ethylenediamine units. Neither of these transaminating systems yet approaches the enantioselectivity seen with a pyridoxamine carrying a chirally mounted internal base group.

Amino Acids↗
PubMed1998

Resistance of aryl-substituted phenylalanines to decarboxylation in the rat.

1. The in vivo decarboxylation of analogues of DL-phenylalanine with methoxy, ethoxy or methylenedioxy substituents on the aromatic nucleus was assessed in the rat by measuring urinary excretion of the corresponding phenylacetic acids and beta-phenylethylamines. Only trace amounts of these amines and acids were excreted. 2. o-Tyrosine was readily decarboxylated, a property that may be attributed to the position and nature of the substituent on the aromatic nucleus. 3. Some phenylpyruvic acids derived from these amino acids exhibited a certain degree of decarboxylation to phenylacetic acids or reduction to phenyllactic acids in the rat.

Animals↗
PubMed1999

Involvement of manganese in conversion of phenylalanine to benzaldehyde by lactic acid bacteria.

We examined the involvement of Mn(II) in the conversion of phenylalanine to benzaldehyde in cell extracts of lactic acid bacteria. Experiments performed with Lactobacillus plantarum demonstrated that Mn(II), present at high levels in this strain, is involved in benzaldehyde formation by catalyzing the conversion of phenylpyruvic acid. Experiments performed with various lactic acid bacterial strains belonging to different genera revealed that benzaldehyde formation in a strain was related to a high Mn(II) level.

Benzaldehydes↗
PubMed1975

Biochemical effects of induced phenylketonuria in rats.

Phenylketonuria (PKU) was induced in rats by the combined feeding of 3 per cent excess phenylalanine and 0.12 per cent of p-chlorophenylalanine, an inhibitor of phenylalanine and tryptophan hydroxylases. Increased concentrations of phenylalanine and increased ratio of phenylalanine to tyrosine were demonstrated in blood from pregnant rats fed the experimental PKU diet from day 10 to 20 of pregnancy, in fetal blood and amniotic fluid of fetal animals from mothers fed the PKU diet, and in blood of rats fed the PKU diet for 28-30 days beginning at 20-21 days of age. Both phenylpyruvic acid and orthohydroxyphenylacetic acid were excreted by rats fed the PKU diet, but neither were detected in urine in animals fed either excess phenylalanine or excess inhibitor alone. Reduced serotonin concentrations were found in brains of rats fed p-chlorophenylalanine, either alone or in combination with excess phenylalanine in the PKU diet. These biochemical changes in rats with induced PKU and the behavioral changes described earlier are similar to those of the human condition. The animal model should prove useful in searching for the mechanism of the disease.

Amino Acids↗
PubMed1975

Gas-liquid chromatography of phenylalanine and its metabolites in serum and urine of various hyperphenylalaninemic subjects, their relatives, and controls.

Phenylalanine and its metabolites were determined in serum and urine of phenylketonuric subjects and in subjects with milder hyperphenylalaninemia in whom blood phenylalanine concentrations were usually less than 200 mg/liter. Metabolite concentrations were related to serum phenylalanine, and in hyperphenylalaninemic subjects were between those for treated and untreated phenylketonuric subjects. Phenyllactic and phenylpyruvic acids were excreted by all of the mild hyperphenylalaninemic subjects except for the youngest (one-year-old twins) and the only subject with a serum phenylalanine of less than 100 mg/liter. Serum and urinary metabolites of heterozygotes of both conditions were similar before and after a phenylalanine load. The similar pattern of metabolites in phenylketonuric and mild hyperphenylalaninemic subjects reinforces the belief that the latter have some phenylalanine hydroxylase activity, and that this is the essential difference between the two groups.

Adolescent↗
PubMed1976

Use of aspartame by apparently healthy children and adolescents.

This study was conducted to determine the effects and the differences, if any, resulting from the ingestion of aspartame (sweetener) versus sucrose. A 13-wk, double-blind study was conducted using 126 apparently healthy children and adolescents as panelists. Individuals were randomly assigned in a double-blind design to aspartame or sucrose in each of five age groups; dosage levels were assigned according to age and weight groups. Physical examinations and special eye examinations were performed at the beginning and end of the study. Other parameters determined including laboratory tests of liver and renal function, hematologic status, and plasma levels of phenylalanine and tyrosine. Clinically significant differences in laboratory parameters measured could not be demonstrated; all mean values were within normal limits. No unusual findings were observed in phenylalanine or tyrosine levels. All phenylpyruvic acid and methanol determinations were negative. No important physical changes occurred, and no product-related side effects were reported.

Acne Vulgaris↗
PubMed1976

[The traps of Guthrie's test].

Presently, 90% of the newborn infants are undergoing screening for phenylketonuria before discharge from the maternity hospital. The tests of detection on urine (search for phenylpyruvic acid) and blood (evaluation of serum phenylalanine) have to be interpreted according to the fetal age, the age at sampling, the conditions of anabolism and the protid intake.

Age Factors↗
PubMed2003

Asbjørn Følling and the discovery of phenylketonuria.

In 1934, the Norwegian biochemist and physician Asbjørn Følling described an inherited metabolic disorder characterized by severe intellectual impairment, motor problems, and skin abnormalities. He found that affected individuals could be identified by the abnormal excretion of phenylpyruvic acid in their urine. The disorder, which Følling initially termed imbecillitas phenylpyrouvica, would later come to be known as phenylketonuria or PKU. The present paper focuses on the story of Følling's discovery and his subsequent contributions to the area of study. In the years that have followed, research on PKU has continued to play a major role in the neurosciences, shaping our understanding of genetic disorders, human metabolism, and brain development.

Female↗
PubMed1970

Metabolism of phenylalanine in mice homozygous for the gene 'dilute lethal'.

Mice homozygous for d(l) have been suggested as models for phenylketonuria. We found: (1) the concentration of phenylalanine in the blood was normal at all ages examined; (2) phenylalanine hydroxylase activity in the liver in vitro equalled that in unaffected littermates; (3) the apparent K(m) values for phenylalanine and cofactor respectively in d(l)/d(l) mice were the same as in their normal littermates; (4) inhibition of the overall reaction by the particulate fraction, excess of substrate, excess of cofactor or phenylpyruvic acid showed no difference between d(l)/d(l) mice and their unaffected littermates; (5) phenylalanine injected in vivo had equal, small, effects on phenylalanine hydroxylase activity of the liver measured in vitro in the two groups of mice. An explanation of the findings of other workers, based on the natural history of the disease process, is tentatively put forward.

Animals↗
PubMed1972

The nature of the collagenolytic cathepsin of rat liver and its distribution in other rat tissues.

1. An enzyme present in rat liver extracts degraded insoluble collagen maximally at pH3.5. Collagenolytic activity was more abundant in kidney, spleen and bone marrow and was also present in decreasing concentrations in ileum, lung, heart, skin and muscle. 2. The crude collagenolytic cathepsin was activated by cysteine and dithiothreitol, but not by 2-mercaptoethanol. Iodoacetamide, p-chloromercuribenzoate and 7-amino-1-chloro-3-l-tosylamidoheptan-2-one hydrochloride inhibited the enzyme. Zn(2+), Fe(3+) and Hg(2+) ions were strongly inhibitory, but Ca(2+), Co(2+), Mg(2+) and Fe(2+) ions had little or no effect. EDTA was an activator of the enzyme. Inhibitors of cathepsin B were found to enhance collagenolysis, but phenylpyruvic acid, a cathepsin D inhibitor, inhibited the enzyme. Di-isopropyl phosphorofluoridate had no effect. 3. Collagenolysis at pH3.5 and 28 degrees C was restricted to cleavage of the telopeptide region in insoluble collagen, and the material that was solubilized consisted mostly of alpha-chains. 4. The collagenolytic cathepsin was separated from cathepsins B2 and D by fractionation on Sephadex G-100 and a partial separation from cathepsin B1 was obtained by chromatography on DEAE-Sephadex. 5. The function of the collagenolytic cathepsin in the catabolism of collagen is discussed in relation to the action of the other lysosomal proteinases and the neutral collagenase.

Animals↗
PubMed1983

Hyperphenylalaninemia with defective transamination.

Blood phenylalanine concentrations in a female neonate increased slowly to a level at which dietary phenylalanine restriction became necessary. At this point the patient's urinary aromatic acid excretion profile showed only minimal amounts of phenylpyruvic acid or related aromatic acids. Phenylalanine-tolerance tests, and a subsequent challenge with a normal diet for three days, revealed a progressive decline in the blood phenylalanine concentration at which transamination started to occur. This fits the classification of 'hyperphenylalaninemia with transamination defect'. Possible explanations for the defective metabolism are discussed in the light of the experimental findings.

Amino Acid Metabolism, Inborn Errors↗
PubMed2004

Inhibitory effects of green tea polyphenols on the production of a virulence factor of the periodontal-disease-causing anaerobic bacterium Porphyromonas gingivalis.

The effect of polyphenolic compounds isolated from green tea (Camellia sinensis) on the production of toxic end metabolites of Porphyromonas gingivalis was investigated. Green tea polyphenols completely inhibited the production of n-butyric acid and propionic acid at a concentration of 1.0-2.0 mg/mL in general anaerobic medium (GAM). (-)-Epigallocatechin gallate (EGCg), which is a major component of tea polyphenols also inhibited the production of phenylacetic acid at 0.5 mg/mL in GAM broth. In the experiment using resting cells of P. gingivalis, phenylacetic acid was produced from l-phenylalanine and phenylpyruvic acid, but this reaction was also inhibited by EGCg, (-)-epicatechin gallate, and (-)-gallocatechin gallate. However, (+)-catechin, (+)-gallocatechin, (-)-epicatechin, and (-)-epigallocatechin did not inhibit those reactions. These results indicate that the inhibitory effect on the production of toxic end metabolites of P. gingivalis can be attributed to the presence of the galloyl moiety, which is ester-linked with the 3-OH of the catechin moiety in the polyphenolic compounds. This study shows that continuous application of tea polyphenols on a daily basis can be considered as a useful and practical method for the prevention of periodontal diseases.

Camellia sinensis↗