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PubMed2000

Metabolism of carnitine in phenylacetic acid-treated rats and in patients with phenylketonuria.

The effect of metabolites accumulating in phenylketonuria (PKU) was investigated on carnitine metabolism in rats and in patients with PKU. Of phenylacetic acid (PEAA), phenylpyruvic acid and homogentisic acid the PEAA was found to be the most effective in inhibiting carnitine biosynthesis in rats. Following 60 min, a single intraperitoneal dose of PEAA the relative conversion rate, i. e. the hydroxylation, of tracer [Me-(3)H]butyrobetaine to [Me-(3)H]carnitine decreased from 62.2+/-6.00% to 39.4+/-5.11% (means+/-S.E.M., P<0.01) in the liver, in the only organ doing this conversion in rats. The conversion of loading amount of unlabeled butyrobetaine to carnitine was also markedly reduced. The impaired hydroxylation of butyrobetaine was reflected by a reduced free and total carnitine levels in the liver and a reduced total carnitine concentration in the plasma. PEAA decreased the hepatic level of glutamic acid and alpha-ketoglutaric acid (alpha-KG), suggesting a mechanism for the reduced flux through the butyrobetaine hydroxylase enzyme, because alpha-KG is an obligatory co-enzyme. In the plasma and urine of PKU patients on unrestricted diet, markedly decreased total carnitine levels were detected. In the liver of PEAA-treated rats and urine of PKU patients, a novel carnitine derivative, phenacetyl-carnitine was verified by HPLC and gas chromatography-mass spectrometry.

Adult↗
PubMed1983

Phenylacetic acid production by Bacteroides gingivalis from phenylalanine and phenylalanine-containing peptides.

Phenylacetic acid production and growth of Bacteroides gingivalis were directly proportional to the trypticase content of the medium. L-Phenylalanine enhanced phenylacetic acid production; 5 mg L-phenylalanine per millilitre stimulated maximum production of phenylacetic acid. Peptides (2-4 amino acids) containing L-phenylalanine also stimulated phenylacetic acid production as did phenylpyruvic acid. Resting cell suspensions of B. gingivalis also produced phenylacetic acid when incubated aerobically in the presence of L-phenylalanine and phenylpyruvic acid. Hydrocinnamic acid (3-phenylpropionic acid) and phenyllactic acid were also produced by resting cell suspensions. Our results suggest that L-phenylalanine and phenylpyruvic acid are both precursors to phenylacetic acid.

Bacteroides↗
PubMed2002

Aromatic amino acid biosynthesis and production of related compounds from p-hydroxyphenylpyruvic acid by rumen bacteria, protozoa and their mixture.

Aromatic amino acid biosynthesis and production of related compounds from p-hydroxyphenylpyruvic acid (HPY) by mixed rumen bacteria (B), protozoa (P), and their mixture (BP) in an in vitro system were quantitatively investigated. Microbial suspensions prepared from mature, fistulated goats fed Lucerne ( Medicago sativa) cubes and a concentrate mixture were anaerobically incubated at 39 degrees C for 12 h. Tyrosine (Tyr), phenylalanine (Phe), tryptophan (Trp) and other related compounds in both supernatants and hydrolyzates of all incubations were analyzed by HPLC. Large amounts of Tyr (27.0, 47.0 and 50.8% of disappeared HPY in B, P and BP, respectively) were produced from 1 mM HPY during a 12-h incubation period. The formation of Tyr in P was 1.8 and 1.6 times higher than those in B and BP, respectively. Appreciable amounts of Phe (3-12% of the disappeared HPY) and Trp (2-10% of the disappeared HPY) were also produced from HPY in B, P, and BP. Phe synthesis in B and P was almost similar but Trp synthesis in B was 1.8 times higher than that in P. The biosynthesis of both Phe and Trp from HPY in BP was higher than those in B plus P. A large amount of p-hydroxyphenylacetic acid (about 45% of the disappeared HPY) was produced from HPY in B which was 1.9 times higher than that in P. p-Hydroxybenzoic acid produced from HPY in P was 1.6 times higher than that in B. Considerable amounts of phenylpropionic acid, phenyllactic acid, and phenylpyruvic acid (2-6% of the disappeared HPY) were produced only in B.

Amino Acids, Aromatic↗
PubMed1976

Efficiency of phenylpyruvic and phenyllactic acids as substitutes for phenylalanine in the diet of the growing rat.

Male weanling albino rats fed a diet containing all nutrients for optimal growth, including 45.4 mumoles of phenylalanine/g, gained weight at an average of 6.5 g/day. Removal of phenylalanine caused an average weight loss of 1.1 g/day. Addition of graduated increments of phenylalanine led to progressive increases in growth rate; the increases being proportional to the dietary content of this amino acid. When phenylpyruvic or L-phenyllactic acids were added isonitrogenously to the phenyl-alanine-free diet, growth rate also increased. Percent efficiency of these amino acid analogues as dietary substitutes for phenylalanine, calculated as (see article) varied from 50% to 70% for phenylpyruvic acid and 65% to 95% for L-phenyllactic acid. Efficiency increased as dose of analogue increased. Non-isonitrogenous substitution did not change growth rates. Supplementation with a megadose of pyridoxine did not increase the efficiency of phenylpyruvic acid. D-phenyllactic acid and cinnamic acid were completely ineffective as substitutes for phenylalanine. When tyrosine was withdrawn from the diet, efficiency of phenylpyruvic acid was 70% at several doses. The efficiency of L-phenyllactic acid was 65 to 40%, decreasing with increasing dose.

Animals↗
PubMed1986

Cell-free biosynthesis of arphamenine A.

Arphamenine A was synthesized in a cell-free system obtained from the arphamenine-producing strain, Chromobacterium violaceum BMG361-CF4. L-[14C]-phenylalanine was converted to beta-phenylpyruvic acid by phenylalanine amino-transferase obtained from the 10,000 x g supernatant (S10 fraction). [14C]-Benzylmalic acid was synthesized from beta-phenylpyruvic acid with [14C]-acetyl-CoA in the S10 fraction. [14C]-Benzylsuccinic acid was formed from beta-phenylpyruvic acid with [14C]-acetyl-CoA and ATP in this fraction, as was [14C]-arphamenine A from benzylsuccinic acid and L-[14C]-arginine. Thus, the pathway of arphamenine A biosynthesis was confirmed by the cell-free biosynthesis of this antibiotic.

Acetyl Coenzyme A↗
PubMed2006

Chemical conversion of alpha-amino acids into alpha-keto acids by 4,5-epoxy-2-decenal.

The comparative formation of phenylalanine and phenylpyruvic acid in the reaction of 4,5-epoxy-2-decenal with phenylalanine was studied to determine whether epoyalkenals may also degrade amino acids without producing their decarboxylation. Both compounds were produced in the reaction to an extent that depended on the reaction pH, the amount of lipid oxidation product, and the reaction time and temperature. The optimum pH was 3 for producing both carbonyl derivatives, and the amount of both compounds increased linearly with the amount of epoxyalkenal present in the reaction mixture. In addition, phenylpyruvic acid was produced to a higher extent than phenylacetaldehyde at 37 degrees C. However, at 60 degrees C the degradation of phenylpyruvic acid was observed and phenylacetaldehyde was usually found to a higher extent than the alpha-keto acid in the overnight-incubated reaction mixtures. The degradation of phenylpyruvic acid produced benzaldehyde and phenylacetaldehyde. All these results suggest that epoxyalkenals can not only degrade amino acids by a Strecker-type mechanism but convert them into their corresponding alpha-keto acids. This new reaction may be an alternative chemical route for the formation in foods of alpha-keto acids, which can later participate in the generation of important amino acid-derived flavor compounds.

Acetaldehyde↗
PubMed1998

Conversion of phenylalanine to benzaldehyde initiated by an aminotransferase in lactobacillus plantarum

The production of benzaldehyde from phenylalanine has been studied in various microorganisms, and several metabolic pathways have been proposed in the literature for the formation of this aromatic flavor compound. In this study, we describe benzaldehyde formation from phenylalanine by using a cell extract of Lactobacillus plantarum. Phenylalanine was initially converted to phenylpyruvic acid by an aminotransferase in the cell extract, and the keto acid was further transformed to benzaldehyde. However, control experiments with boiled cell extract revealed that the subsequent conversion of phenylpyruvic acid was a chemical oxidation step. It was observed that several cations could replace the extract in the conversion of phenylpyruvic acid to benzaldehyde. Addition of Cu(II) ions to phenylpyruvic acid resulted not only in the formation of benzaldehyde, but also in the generation of phenylacetic acid, mandelic acid, and phenylglyoxylic acid. These compounds have been considered intermediates in the biological conversion of phenylalanine. The chemical conversion step of phenylpyruvic acid was dependent on temperature, pH, the availability of cations, and the presence of oxygen.

Journal Article↗
PubMed2005

Engineered phenylalanine dehydrogenase in organic solvents: homogeneous and biphasic enzymatic reactions.

The use of engineered phenylalanine dehydrogenase N145A supported on Celite for the reductive amination of phenylpyruvic acid in homogeneous and biphasic aqueous-organic solvents is reported. The results indicate that the immobilised biocatalyst is remarkably robust, even in the presence of high concentrations of polar or non-polar organic solvents such as acetone, methanol, n-hexane, toluene and methylene chloride. Cofactor regeneration with alcohol dehydrogenase from Saccharomyces cerevisiae and ethanol was successfully explored. Application to the non-natural poorly water-soluble 2-oxo acid p-NO(2)-phenylpyruvic acid was successfully performed, resulting in the biocatalytic synthesis of p-NO(2)-phenylalanine. In all cases 100% stereoselectivity for the production of the amino acid was retained.

Amino Acid Oxidoreductases↗
PubMed1983

[Biosynthesis of phenylalanine and tyrosine in Streptomycetes].

The biosynthesis of phenylalanine and tyrosine from prephenic acid may proceed via phenylpyruvic acid or p-hydroxyphenylpyruvic acid or via arogenate. The enzymes necessary for these biosynthetic steps have been tested in a variety of Streptomycetes. Tyrosine is synthesized exclusively via arogenate, while phenylalanine is synthesized via phenylpyruvic acid. The feedback inhibition pattern of the corresponding enzymes has been determined. The organisms may be divided into four groups according to the properties of the phenylalanine and tyrosine biosynthetic enzymes and their regulation patterns.

Feedback↗
PubMed1993

Comparative metabolism and structure of BCKD-E2 in primary biliary cirrhosis.

The identification and cloning of the mitochondrial autoantigens in primary biliary cirrhosis (PBC) have provided new clues in disease pathogenesis. The two major autoantigens are the E2 subunits of pyruvate dehydrogenase and branched-chain ketoacid dehydrogenase (BCKD). Interestingly, one of these complexes, BCKD-E2, is already well known to clinical medicine based on its association with genetic mutations in maple syrup urine disease (MSUD). Patients with this disease have an inability to metabolize branched-chain amino acids. In the present study, we have taken advantage of the known sequence of BCKD-E2 from normal humans, and addressed the issue of whether there is an altered autoantigen sequence in hepatocytes of individuals with primary biliary cirrhosis. In particular, we examined both the leader sequence and the B-cell immunodominant epitope, the lipoic acid domain. In addition, because patients with PBC have autoantibodies to the BCKD-E2 complex, we have quantitated plasma levels of alpha-ketoacids potentially affected in maple syrup urine disease. These include pyruvic acid (PY), phenylpyruvic acid (PP), alpha-ketoisocaproic acid (KIC) alpha-ketoisovalerate (KIV) and alpha-keto-beta-methylvaleric acid (KMV). The levels of these alpha-ketoacids were compared in patients with primary sclerosing cholangitis and normal volunteers. The sequence of BCKD-E2 obtained from PBC hepatocytes showed homology with normal BCKD. Further studies of autoantigen structure and sequence are clearly indicated, including those involved in mitochondrial transport and localization. Finally, we noted a statistically significant increase in all plasma alpha-ketoacids except alpha-keto-beta-methylvaleric acid in PBC patients.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed1980

[Excretion of transamination products in hyperphenylalaninemia (author's transl)].

A low-phenylalanine diet was given for a period of three weeks to four untreated adult phenylketonurics with mental deficiency. One week before the diet was started, in the course of the diet and one week after its termination, some transamination products of phenylalanine, tryptophan and histidine were determined quantitatively. Each of the transamination products showed a positive correlation to the serum phenylalanine levels of the patients, probably due to the large affinity of 4-hydroxyphenylpyruvic acid and phenylpyruvic acid for the amino groups of the aromatic amino acids. This may also explain the low levels of epinephrine, norepinephrine and serotonine which has been observed by other authors in untreated phenylketonurics. Accordingly, treated phenylketonurics should suffer from a chronic deficiency of biogenic amines after termination of the low-phenylalanine diet.

Adult↗
PubMed1984

Fluorescent analysis of alpha-keto acids in serum and urine by high-performance liquid chromatography.

A procedure for rapid separation and microquantitative determination of various alpha-keto acids in serum and urine was developed. The procedure used reverse-phase high-performance liquid chromatography of the alpha-keto acids after derivatization into fluorescent quinoxalines by reaction with o-phenylenediamine. Deproteinization of serum with tungstic acid or methanol facilitated a constant recovery of alpha-keto acids. The useful range of analysis of seven alpha-keto acids by isocratic chromatography was from 10 to 250 pmol. The fluorescence emission was measured at 410 nm with excitation at 350 nm. The data obtained from samples of patients with chronic pyruvic acidemia and maple syrup urine disease, confirmed the usefulness of the method in clinical applications. A slightly modified procedure was needed for the analysis of oxaloacetic acid and phenylpyruvic acid.

Chromatography, High Pressure Liquid↗
PubMed1995

Rapid determination of phenylalanine and its related compounds in rumen fluid by high-performance liquid chromatography.

A rapid method for the determination of phenylalanine (Phe), tyrosine (Tyr), benzoic acid (BZA), phenylacetic acid (PAA), phenyllactic acid (PLA), phenylpyruvic acid (PPY), phenylpropionic acid (PPR), and cinnamic acid (CNM) in goat rumen fluid was established by high-performance liquid chromatography (HPLC). The mobile phase used for isocratic elution was methanol-sodium acetate buffer (pH 6.5) (8:92, v/v). The compounds were monitored at 220 nm with a UV detector. A 5-microliters portion of the filtrated rumen fluid was analyzed and the analysis was completed within 20 min. The minimum detectable limits (microM) of these compounds were: 12 for Phe, 3 for Tyr, 3 for BZA, 9 for PAA, 12 for PLA, 15 for PPY, 20 for PPR, and 8 for CNM. The average contents of Phe, BZA, PAA, PLA, and PPR in the rumen fluid of three goats were 15.4, 73.7, 615.9, 51.1, and 39.9 microM before morning feeding, 17.0, 123.7, 650.4, 208.2, and 502.4 microM at 3 h after feeding, and 18.4, 124.2, 510.0, 129.9, and 178.5 microM at 6 h after feeding, respectively. Of these compounds PAA was present at the highest concentration both before and after feeding. The content of PPR extremely increased especially at 3 h after feeding. The other three compounds, i.e. Tyr, PPY, and CNM, were not detected in goat rumen fluid.

Amino Acids↗
PubMed1998

Quantitative determination of aromatic amino acids and related compounds in rumen fluid by high-performance liquid chromatography.

A rapid method for the quantitative determination of tyrosine (Tyr), phenylalanine (Phe), p-hydroxybenzoic acid (HBA), p-hydroxyphenylacetic acid (HPA), benzoic acid (BZA), p-hydroxyphenylpyruvic acid (HPY), phenylacetic acid (PAA), phenyllactic acid (PLA), tryptophan (Trp), indoleacetic acid (IAA), phenylpyruvic acid (PPY), phenylpropionic acid (PPA) and cinnamic acid (CNA) in goat rumen fluid was established by high-performance liquid chromatography (HPLC). The mobile phase used for isocratic elution was 50 mM sodium phosphate buffer (pH 6.5)-methanol (97:3, v/v). The flow-rate was 1.0 ml/min; column temperature 40 degrees C and compounds were monitored at 215 nm with a UV absorbance detector after injection of 10 microl of filtered rumen fluid. Analysis was completed within 40 min. The minimum detectable limits of quantification (microM) of these compounds were Tyr, 2; Phe, 3; HBA, 1; HPA, 2; BZA, 2; HPY, 8; PAA, 3; PLA, 4; Trp, 2; IAA, 2; PPY, 15; PPA, 8 and CNA, 4. Detectable levels of Tyr, Phe, HPA, BZA, HPY, PAA, PLA, Trp and PPA were found in the deproteinized rumen fluid of goat fed a haycube and concentrate mixture. PAA was the predominant compound before and after feeding. The concentrations of HPA, BZA, PAA, PLA and PPA in the goat rumen fluid increased after feeding, while the concentration of Tyr decreased. Phe, HPY and Trp were minor components at all times. PPY, IAA and CNA were not detected and HBA was not completely resolved in the goat rumen fluid.

Amino Acids↗
PubMed1975

Statistical evaluation of a new method to detect carriers of phenylketonuria.

40 positive heterozygotes and 43 controls were loaded with 200 mg phenylalanine per kilogram body weight. The aromatic acids excreted 2 hrs after the loading were quantified by gaschromatography. The amounts of mandelic acid (MA), 2-hydroxyphenylacetic acid (2HOPAA) and phenylpyruvic acid (PPA) were used for a discriminatory analysis. The MA concentration alone gives a better discrimination than the statistical analysis.

Evaluation Studies as Topic↗
PubMed1969

Inhibition of human brain pyruvate kinase and hexokinase by phenylalanine and phenylpyruvate: possible relevance to phenylketonuric brain damage.

In phenylketonuria high levels of L-phenylalanine are present along with increased levels of phenylpyruvic acid. The present work shows that L-phenylalanine is a competitive inhibitor of human brain pyruvate kinase and phenylpyruvic acid is an inhibitor of human brain hexokinase. The enzymes have approximately the same K(i) for these inhibitors in adult and in fetal human brain. However, in the fetal human brain the absolute activities for both enzymes are less than 10 per cent of those found in the adult. Thus, the fetal brain enzymes may be more vulnerable to inhibition by these compounds in the phenylketonurics. The inhibition of human brain pyruvate kinase and hexokinase by L-phenylalanine and phenylpyruvic acid may have a role in the brain damage in phenylketonurics.

Aging↗
PubMed1993

Effect of the immediate precursors of phenylalanine and tyrosine on growth and protein synthesis in phenylalanine- and tyrosine-deprived HeLa cells.

Although Phe is an essential amino acid in mammalian cells, its immediate precursor, beta-phenylpyruvic acid (BPP), when present in Phe-deficient medium at 10(-4) and 10(-3) M is converted at a sufficient rate to Phe to sustain growth at 60 and 100% of non-deficient control HeLa S-3 cells, respectively. In contrast, Tyr-deficient cells were unable to convert the immediate precursor of Tyr, OH-beta-phenylpyruvic acid (OHBPP), nor could BPP rescue Tyr-deficient cells. The results are considered in terms of the organization of intracellular pathways by which precursors are transaminated and made available for protein synthesis.

Cell Division↗