Conversion Of Phenylalanine Research Articles

Conversion of phenylalanine to toluene and 2-phenylethanol by the pine engraverIps pini (Say) (Coleoptera, Scolytidae)

The pine engraver,Ips pini (Say), was found to produce toluene and 2-phenylethanol when boring into fresh pine logs. The hypotheses that phenylalanine is a precursor of these compounds and that beetles without their symbiotic microorganisms can perform these conversions were confirmed by treating wild and axencially-reared males and females topically with L-phenyl-d5-alanine. Extracts of these beetles invariably contained deuterio-toluene, and extracts of males contained deuterio-2-phenylethanol as well.

ChemInform Abstract: Peptides Containing Dialkylglycines. Part 3. The Alkylation of 2‐Trifluoromethyl‐4‐alkyloxazolin‐5(2H)‐ones, and Partition Studies on N‐Acetyl‐αα‐dialkylglycinamides.

AbstractThe conversion of phenylalanine (I) into (V) (X,Y: ‐CH2‐Ph) is shown in the reaction scheme as an example of the preparation of the glycine amide derivatives (V).

Biochemical characterization of recombinant human phenylalanine hydroxylase produced in Escherichia coli.

A full-length human phenylalanine hydroxylase cDNA has been recombined with a prokaryotic expression vector and introduced into Escherichia coli. Transformed bacteria express phenylalanine hydroxylase immunoreactive protein and pterin-dependent conversion of phenylalanine to tyrosine. Recombinant human phenylalanine hydroxylase produced in E. coli has been partially purified, and biochemical studies have been performed comparing the activity and kinetics of the recombinant enzyme with native phenylalanine hydroxylase from human liver. The optimal reaction conditions, kinetic constants, and sensitivity to inhibition by aromatic amino acids are the same for recombinant phenylalanine hydroxylase and native phenylalanine hydroxylase. These data indicate that the recombinant human phenylalanine hydroxylase is an authentic and complete phenylalanine hydroxylase enzyme and that the characteristic aspects of phenylalanine hydroxylase enzymatic activity are determined by a single gene product and can be constituted in the absence of any specific accessory functions of the eukaryotic cell. The availability of recombinant human phenylalanine hydroxylase produced in E. coli will expedite physical and chemical characterization of human phenylalanine hydroxylase which has been hindered in the past by inavailability of the native enzyme for study.

タケノコ組織中へのL-フェニルアラニン-U-<sup>14</sup>C及びL-チロシン-U-<sup>14</sup>Cのトレーサー実験

Uniformly 14C-labeled L-phenylalanine and L-tyrosine were administered to tissue slices of both top and base sections of bamboo shoots. Alcohol soluble substances were extracted and then separated into organic acid, sugar and amino acid fractions by ion exchange chromatography. The homogentisic acid fraction among the organic acids was collected by high-performance liquid chromatography (HPLC) and its radioactivity was measured, while the alcohol insoluble residue was used for the analysis of lignin aldehyde by the method of alkaline nitrobenzene oxidation.1. The two labeled amino acids were steadily incorporated into the tissues during incubation and rapidly converted to organic acid, sugar and alcohol insoluble residue, especially the latter.2. On determining the amount of phenylalanine converted to tyrosine, it was found that this was extremely small.3. The incorporation of phenylalanine-U-14C into alcohol insoluble residue was higher than that of tyrosine in both sections.4. Although the conversion into lignin aldehyde from phenylalanine-U-14C was higher than that from tyrosine-U-14C, it was found that tyrosine incorporated into the shoots was converted to a remarkable extent for formation of lignin aldehyde.5. The incorporation of phenylalanine and tyrosine into homogentisic acid was very low.From these results, we assume that the conversion of phenylalanine to tyrosine or of tyrosine to homogentisic acid is very small, and that a part of the high amount of tyrosine in the shoots may be used for formation of lignin.

Biosynthesis of antibiotics of the virginiamycin family, 5. The conversion of phenylalanine to phenylglycine in the biosynthesis of virginiamycin S1.

Conversion of L-phenylalanine to L-phenylglycine in the biosynthesis of virginiamycin S1 (1) can, in principle, take place with intramolecular nitrogen transfer or with intermolecular nitrogen transfer. A labeling experiment with DL-[3-13C, 15N]phenylalanine showed that the resulting L-phenylglycine contained no labeled nitrogen, indicating that the rearrangement proceeds via an intermolecular pathway.

Molecular structure and polymorphic map of the human phenylalanine hydroxylase gene

Human phenylalanine hydroxylase is a liver-specific enzyme that catalyzes the conversion of phenylalanine to tyrosine. Absence of enzymatic activity results in phenylketonuria, a genetic disorder that causes development of severe mental retardation in untreated children. In this paper we report the cloning and structure of the normal human phenylalanine hydroxylase gene, which was isolated in four overlapping cosmid clones that span more than 125 kilobases (kb) of the genetic locus. The peptide coding region of the gene is about 90 kb in length and contains 13 exons, with intron sizes ranging from 1 to 23 kb. Exons at the 3' half of the gene are compact, whereas those at the 5' half are separated by large introns. The human phenylalanine hydroxylase gene codes for a mature messenger RNA of approximately 2.4 kb, and its noncoding to coding DNA ratio is one of the highest among eukaryotic genes characterized to date. The map positions of nine polymorphic restriction sites identified within the locus were established by restriction enzyme mapping of the cloned gene fragments. Two clusters of polymorphic sites were demonstrated: (1) BglII, PvuII(a), and PvuII(b) at the 5' end of the gene and (2) EcoRI, XmnI, MspI(a), MspI(b), EcoRV, and HindIII at the 3' end. The polymorphic site distribution within this gene is a useful tool for prenatal diagnosis and carrier detection of the genetic disorder, while knowledge of normal gene structure is a prerequisite for future characterization of mutant alleles.

Comparative composition of free, peptide and protein amino acids in symbiotic and aposymbiotic Sitophilus oryzae (coleoptera, curculionidae)

Free, peptide-bound and total amino acids were determined in symbiotic and aposymbiotic Sitophilus oryzae. The concentrations of free and peptide amino acids were higher, that of protein amino acids lower in aposymbiotic larvae (+30, +66 and −35%, respectively). In the free fraction, tyrosine concentration was the only one to be lower in aposymbiotic larvae (−41%) and could be a limiting factor for protein synthesis. In nymphs and adults, the compositions in symbiotic and aposymbiotic insects were very similar. A deficiency of tyrosine occurred however in aposymbiotic nymphs and of aspartate, glutamate, arginine, lysine and tyrosine in aposymbiotic adults. On the other hand, the composition in ovaries was unchanged. It is suggested that symbiotes could favour the synthesis of proteins in the larvae by increasing the efficiency of the conversion of phenylalanine in tyrosine.

The metabolism of cinnamic acid by healthy and phenylketonuric adults: a kinetic study.

The enzyme phenylalanine ammonia lyase taken orally has been found to reduce the rise in blood phenylalanine that normally occurs following a protein meal. Therefore the enzyme has a potential use in the management of the genetic disease phenylketonuria. The enzyme mediates the conversion of phenylalanine to cinnamic acid and its possible clinical future has necessitated a more detailed study of the product of its reaction. Cinnamic acid is a compound of low toxicity which is converted in the mammalian body primarily to hippuric acid. We have examined the kinetics of this process in a healthy male and in two patients with untreated phenylketonuria. In addition we have attempted to clarify the inconsistencies in earlier published work about the status of other, minor metabolites. Following an oral load of sodium (2H6) cinnamate there is an increase in urinary hippuric acid largely due to the excretion of (2H5) hippuric acid. In the subjects studied there was no major difference in the rate of elimination although the amount of cinnamic acid converted was less in those with phenylketonuria. This may reflect reduced first-pass absorption by the liver in untreated phenylketonuria enabling increased uptake to occur in other parts of the body.

The contribution of phenylalanine to tyrosine metabolism in vivo. Studies in the post-absorptive and phenylalanine-loaded rat.

1. Rates of appearance and oxidation of plasma L-leucine, L-phenylalanine and L-tyrosine, as well as conversion of plasma phenylalanine into plasma tyrosine, were determined in 90-120 g rats after overnight starvation and while receiving 115-120 mumol of L-phenylalanine/h. 2. In the post-absorptive state, plasma tyrosine and phenylalanine appearances were similar, despite the fact that 22% of plasma tyrosine appearance could be attributed to the hydroxylation of phenylalanine. 3. A constant infusion of 115-120 mumol of L-phenylalanine/h did not significantly alter plasma leucine kinetics, but increased appearance of plasma phenylalanine and tyrosine. The percentage of phenylalanine and tyrosine appearance that was oxidized increased from 12.1% and 24.4% to 37.3% and 48.0% respectively. In phenylalanine-loaded rats, 72% of plasma tyrosine appearance could be attributed to the conversion of phenylalanine. 4. Whole-body tyrosine oxidation measured from a continuous infusion of either L-[14C]tyrosine or L-[14C]phenylalanine differed by 165%. 5. It can be concluded that, in the post-absorptive state, phenylalanine hydroxylation makes a substantial contribution to the plasma appearance of tyrosine and is significantly increased when phenylalanine is administered. The disposal of excess infused phenylalanine is a result of a greater percentage of plasma phenylalanine being converted into tyrosine and a greater proportion of tyrosine being further oxidized. However, apparent tyrosine oxidation rates estimated from plasma tyrosine specific radioactivities and appearance of expired 14CO2 during administration of [14C]tyrosine are underestimates of true rates, in part because tyrosine generated from phenylalanine hydroxylation is catabolized without freely equilibrating with the plasma compartment.

Metabolism of aromatic acids in the antibiotic-producing basidiomycete Oudemansiella mucida.

Aromatic acids were determined in the mycelium and fermentation medium of Oudemansiella mucida. Coumaric acids (both m- and p-), p-hydroxybenzoic acid (salicylic acid) and benzoic acid were found to predominate in the mycelium. Phenylacetic acid represents the main component in the medium. Phenylalanine ammonia-lyase catalyzing conversion of phenylalanine to cinnamic acid which is further metabolized to benzoic acid was detected in the mycelium. The results are discussed with respect to the synthesis of the antibiotic mucidin.

The conversion of phenylalanine to tyrosine in man. Direct measurement by continuous intravenous tracer infusions of L-[ ring- 2H 5]phenylalanine and L-[1- 13C]tyrosine in the postabsorptive state

Steady state phenylalanine and tyrosine turnover and the rate of conversion of phenylalanine to tyrosine in vivo were determined in 6 healthy postabsorptive adult volunteers. Continuous infusions of tracer amounts of L-[ ring- 2H 5]phenylalanine were administered intravenously for 13–14 hr. After 9–10 hr, a priming dose followed by a continuous infusion of L-[1- 13C]tyrosine was added and maintained, along with the [ 2H 5]phenylalanine infusion, for 4 hr. Venous plasma samples were obtained before the initiation of each infusion and every 30 min during the course of the combined [ 2H 5]phenylalanine and [ 13C]tyrosine infusion for determination of isotopic enrichments of [ 2H 5]phenylalanine, [ 13C]tyrosine, and [ 2H 4[tyrosine by gas chromatograph-mass spectrometric analysis of the N-trifluoroacetyl-, methyl ester derivatives of the amino acids. Calculated from the observed enrichments, free phenylalanine and tyrosine turnover rates were 36.1 ± 5.1 μmole · kg −1 · h −1 and 39.8 ± 3.5 μmole · kg −1 · h −1, respectively. Phenylalanine was converted to tyrosine at the rate of 5.83 ± 0.59 μmole · kg −1 · h −1, accounting for approximately 16% of either the phenylalanine or the tyrosine flux. The results indicate that the normal basal steady state phenylalanine hydroxylase activity in vivo in man is lower than that obtained from phenylalanine loading studies. This supports the existence of some type of substrate activation of the enzyme as reflected in the previously reported exponential relationship between phenylalanine concentration and phenylalanine hydroxylase activity in vitro. The use of continuous simultaneous infusions of tracer amounts of stable isotope-labeled phenylalanine and tyrosine provides a direct means for studying physiological regulation of phenylalanine hydroxylase activity in vivo.

A laboratory experiment in protein biosynthesis: The conversion of free phenylalanine to ribosome-bound phenylalanine

A laboratory experiment in protein biosynthesis: The conversion of free phenylalanine to ribosome-bound phenylalanine

Phenylalanine metabolism in Microtus montanus chronically infected with Trypanosoma brucei gambiense

1. 1. Alterations in phenylalanine metabolism were observed in Microtus montanus infected with Trypanosoma brucei gambiense. 2. 2. Reductions were found in the incorporation of phenylalanine into free amino acid pools and into proteins of the liver and other organs of infected animals. 3. 3. Increased quantities of phenylpyruvate, 4-hydroxyphenylpyruvate and pyruvate were found in the urine of infected Microtus. 4. 4. There appeared to be very limited conversion of phenylalanine to tyrosine in infected animals. This suggested that either phenylalanine transaminase activity was greatly elevated in proportion to phenylalanine hydroxylase activity; or that phenylalanine hydroxylase activity was actually reduced during the infection.

Phenylketonuric Tetrahymena: phenylalanine hydroxylase mutants and other tyrosine auxotrophs.

Nineteen tyrosine auxotrophs of the ciliated protozoan Tetrahymena thermophila have been isolated and biochemically examined. These mutants are defective in the conversion of phenylalanine to tyrosine; this is analogous to the defect that causes phenylketonuria in humans. After nitrosoguanidine mutagenesis and self-fertilization, progeny clones were screened for tyrosine auxotrophy and positively identified by using growth tests and in vivo radiometric assays for phenylalanine-to-tyrosine conversion. Mutants in one complementation group (locus) lacked phenylalanine hydroxylase activity; mutants in three other loci appeared to be deficient in the unconjugated pteridine cofactor that is necessary for the function of the hydroxylase. Another mutant lacked the dihydropteridine reductase activity required to regenerate the reduced form of the pteridine cofactor. Because hydroxylation of tyrosine to dopa and of tryptophan to 5-hydroxytryptophan may require the same cofactor and pterin reductase as phenylalanine hydroxylase, these mutants may also prove useful for the study of the role of catecholamines and serotonin, substances known to be present in Tetrahymena.

Conversion of Phenylalanine into Tyrosine by Portulaca Callus

The incorporation of [(14)C]phenylalanine and [1,6-(14)C]shikimic acid into tyrosine was investigated in the callus of Portulaca grandiflora, var. JR (L.). By inhibiting phenylalanine with 1-alpha-aminooxy-beta-phenyl-propionic acid and tyrosinase with 1-cysteine-HCl and hydrazine-hydrate, the possible synthesis of tyrosine from phenylalanine was demonstrated. Tetrahydropterine sulfate was an effective activator of this pathway and tyrosine accumulation via 4-hydroxy-prephenic acid is regulated by feedback inhibition. l-alpha-Amminooxy-beta-phenylpropionic acid inhibits both phenylalanine ammonia-lyase and the production of phenylalanine from prephenic acid.

Bacterial conversion of phenylalanine and aromatic carboxylic acids into dihydrodiols.

Strain E of chloridazon-degrading bacteria, when grown on L-phenylalanine accumulates cis-2,3-dihydro-2,3-dihydroxyphenylalanine. In experiments with resting cells and during growth the bacterium converts the aromatic carboxylic acids phenylacetate, phenylpropionate, phenylbutyrate and phenyl-lactate into the corresponding cis-2,3-dihydrodiol compounds. The amino acids L-phenylalanine, N-acetyl-L-phenylalanine and t-butyloxycarbonyl-L-phenylalanine were also transformed into dihydrodiols. All seven dihydrodiols, thus obtained, were characterized both by conventional analytical techniques and by the ability to serve as substrates for a cis-dihydrodiol dehydrogenase.

New Developments in Hyperphenylalaninemia

In recent years it has become apparent that hyperphenylalaninemia in newborn infants may be caused by a variety of defects in the enzyme phenylalanine hydroxylase or by an abnormality in either the enzyme dihydropteridine reductase (DHPR) or the synthesis of dihydrobiopterin (BH2) (Figure). Despite the rarity of the latter conditions1 there are important implications for management in making this diagnosis. It has been suggested that all new cases of hyperphenylalaninemia now be screened for these variants.2 The purpose of the Task Force was to define the feasibility of this course at the present time. BACKGROUND The hepatic system for conversion of phenylalanine to tyrosine is complex and consists of at least two essential enzymes, phenylalanine hydroxylase (catalyzing reaction 1) and dihydropteridine reductase (catalyzing reaction 2), and an essential, nonprotein cofactor, tetrahydrobiopterin3: (1) Phenylalanine + O2 + tetrahydrobiopterin → tyrosine + H2O + quinonoid dihydrobiopterin; (2) nicotinamide adenine dinucleotide (reduced form) + H+ + quinonoid dihydrobiopterin → nicotinamide adenine dinucleotide (oxidized form) + tetrahydrobiopterin. Most cases of hyperphenylalaninemia detected by newborn infant screening programs are caused by deficiencies of phenylalanine hydroxylase ranging from the severe "classic phenylketonuria (PKU)" to the more benign "hyperphenylalaninemic variant." The patients with classic PKU usually respond to a diet low in phenylalanine. However, of the estimated 400 cases of classic PKU detected annually in the United States, up to 3% may show progressive neurologic deterioration despite adequate dietary treatment. The elevated phenylalanine in these infants may be caused by either DHPR deficiency or a deficient synthesis of BH2 or to other still unidentified causes.

Phenylalanine analogues as inhibitors of phenylalanine-hydroxylase from rat liver: New conclusions concerning kinetic behaviors of the enzyme

The conversion of phenylalanine to tyrosine is catalysed by phenylalanine-hydroxylase. The substrate phenylalanine shows two effects: (1) allosteric transition at low phenylalanine concentrations, (2) excess substration inhibition. The molecular structure of phenylalanine-hydroxylase has not yet been elucidated. However, a tetrameric structure has been proposed. The Kinetic analysis with respect to substrate analogues suggest the existence of three types of sites on each protomer: (1) a catalytic site, (2) a non-competitive inhibitory site, (3) a positive cooperative site. Use of the enzyme's natural cofactor, tetrahydrobiopterin, has been emphasized to ensure good interpretation of the kinetic results of the phenylalanine-hydroxylase effectors.

Phenylalanine hydroxylase in melanoma cells.

A pigmented subclone of Cloudman S91 melanoma cells, PS1-wild type, can grow in medium lacking tyrosine. This ability is conferred by phenylalanine hydroxylase activity, and not by tryptophan hydroxylase, tyrosine hydroxylase or tyrosinase activities, although the latter activity is also present in these cells. Conversion of phenylalanine to tyrosine was measured in living cells by chromatographic identification of the metabolites of [14C]phenylalanine and in cell extracts using a sensitive assay for phenylalanine hydroxylase. Phenylalanine hydroxylase activity in melanoma cell extracts was identified by its inhibition with p-chlorophenylalanine and not with 6-fluorotryptophan, 3-iodotyrosine, phenylthiourea, tyrosine or tryptophan; and by adsorption with antiserum prepared against purified rat liver phenylalanine hydroxylase, and migration of immunoprecipitable activity with authentic phenylalanine hydroxylase subunits in sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Phenylketonuria: a new method for the simultaneous determination of plasma phenylalanine and tyrosine.

This quantitative spectrophotometric method is based on the conversion of phenylalanine and tyrosine by phenylalanine ammonia-lyase to trans-cinnamic acid and trans-coumaric acid, respectively. Neither deproteinization nor prior incubation of the sample is required, and the entire procedure can be performed in 20 minutes. The method is sensitive to 1-micromolar concentrations of the two compounds, and only 20 microliters of plasma or serum is required to determine both phenylalanine and tyrosine simultaneously. These amino acids were determined between molar ratios (phenylalanine to tyrosine) of 0.1 to 40 in the serum or plasma of healthy individuals and plasma of phenylketonuric patients.