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4-(4′-Acetoxybenzylidine)-2-methyl-5-oxazolone (Z-isomer) was synthesized, which upon basic hydrolysis yielded the unexpected 2-acetoxy-3-(p-hydroxyphenyl)-propenoic acid and treatment with acetic acid formed 2-acetoxy-3-(p-acetoxyphenyl)-propenoic acid. The structures of the three compounds were assigned by NMR spectroscopy. An X-ray crystallographic study of the starting azlactone confirmed its structure and supported the fact that the Z-configuration was retained during the synthesis of the phenylpropenoic acid derivatives.

The double carbonylation of benzyl chloride to phenylpyruvic acid (PPA) catalyzed by CoCl 2 ·6H 2 O and potassium pyridine-2-carboxylate (KPyca) in Ca(OH) 2 /dioxane/H 2 O system has been studied. The effects of ligands, concentration of catalysts, solvents, temperature, CO pressure and the molar ratio of Ca(OH) 2 /PhCH 2 Cl on the conversion and selectivity have been investigated. The conversion of benzyl chloride was 71.3%, and the yield of PPA was 70.1% with selectivity 98.3% when the reaction was carried out for 10 h at 353 K and 2.8 MPa of CO in the Ca(OH) 2 /dioxane/H 2 O system, with CoCl 2 0.035 mol/l, KPyca 0.13 mol/l, and the ratio of Ca(OH) 2 /PhCH 2 Cl 2.0. The product PPA was characterized by IR, 1 H NMR, MS and UV. The mechanism of this catalytic reaction has also been discussed.

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.

The catabolism of amino acids by cheese micro-organisms results in the production of various volatile flavour compounds. It was recently shown to be a rate-limiting factor in the formation of cheese flavour, leading to an increased interest in elucidating the pathways and the flora involved. This paper reviews the ability of propionibacteria (PAB) to produce flavour compounds deriving from branched-chain, aromatic and sulphur-containing amino acids. In culture media, PAB produced volatile compounds derived from Leu, Ile, Met and Phe. In cheese, the presence of PAB is positively correlated to the amount of acids, alcohols and/or aldehydes derived from Leu or Ile. The metabolic pathways of amino acid conversion to flavour compounds by PAB have been only partly elucidated. Aminotransferase(s) catalyse the first step of conversion of branched-chain, aromatic amino acids and methionine, with a higher activity for branched-chain amino acids. The α-keto acids resulting from transamination are further degraded to various compounds by resting cells of PAB. So α-ketoisocaproic acid, derived from Leu, is essentially converted to isovaleric acid by a ketoacid dehydrogenase complex; phenylpyruvic acid, derived from Phe, is converted to phenyllactic acid, phenylacetic acid, benzoic acid and benzaldehyde. Methionine can also be directly degraded by α, γ -elimination, leading to methanethiol. The amino acid catabolism pathways in PAB share similar- ities with those of lactic acid bacteria but PAB seem to produce higher amounts of branched-chain ac- ids, which are important flavour compounds in cheese. propionibacteria / flavour compound / amino acid / catabolism / cheese ripening

The Tyr52 residue of D-lactate dehydrogenase (D-LDH) from Lactobacillus pentosus was replaced with small hydrophobic residues and overexpressed in E. coli BL21 (DE3) to enhance 3-phenyllactic acid (PLA) synthesis by whole-cell catalyst.Escherichia coli pET-28a-d-ldh produced 12.2 g PLA l(-1) in 3 h, with a molar conversion rate of 61 %, while E. coli pET-28a-d-ldh (Y52V) produced 15.6 g PLA l(-1), with a molar conversion rate of 77 %. This study demonstrates the feasibility of using engineered E. coli for PLA production from phenylpyruvate (PPA) and showed that site-directed mutagenesis of d-ldh markedly improved PLA yield and substrate conversion rate.This biocatalytic system is a promising platform for PLA production from PPA.

Methyl jasmonate has a strong effect on secondary metabolizm in plants, by stimulating the biosynthesis a number of phenolic compounds and alkaloids. Common buckwheat (Fagopyrum esculentum Moench) is an important source of biologically active compounds. This research focuses on the detection and quantification of 2-phenylethylamine and its possible metabolites in the cotyledons, hypocotyl and roots of common buckwheat seedlings treated with methyl jasmonate. In cotyledons of buckwheat sprouts, only traces of 2-phenylethylamine were found, while in the hypocotyl and roots its concentration was about 150 and 1000-times higher, respectively. Treatment with methyl jasmonate resulted in a 4-fold increase of the 2-phenylethylamine level in the cotyledons of 7-day buckwheat seedlings, and an 11-fold and 5-fold increase in hypocotyl and roots, respectively. Methyl jasmonate treatment led also to about 4-fold increase of phenylacetic acid content in all examined seedling organs, but did not affect the 2-phenylethanol level in cotyledons, and slightly enhanced in hypocotyl and roots. It has been suggested that 2-phenylethylamine is a substrate for the biosynthesis of phenylacetic acid and 2-phenylethanol, as well as cinnamoyl 2-phenethylamide. In organs of buckwheat seedling treated with methyl jasmonate, higher amounts of aromatic amino acid transaminase mRNA were found. The enzyme can be involved in the synthesis of phenylpyruvic acid, but the presence of this compound could not be confirmed in any of the examined organs of common buckwheat seedling.

Although it is recognized that the abnormal accumulation of amino acid is a cause of the symptoms in metabolic disease such as phenylketonuria (PKU), the relationship between disease severity and serum amino acid levels is not well understood due to the lack of experimental model. Here, we present a novel in vitro cellular model using K562-D cells that proliferate slowly in the presence of excessive amount of phenylalanine within the clinically observed range, but not phenylpyruvate. The increased expression of the L-type amino acid transporter (LAT2) and its adapter protein 4F2 heavy chain appeared to be responsible for the higher sensitivity to phenylalanine in K562-D cells. Supplementation with valine over phenylalanine effectively restored cell proliferation, although other amino acids did not improve K562-D cell proliferation over phenylalanine. Biochemical analysis revealed mammalian target of rapamycin complex (mTORC) as a terminal target of phenylalanine in K562-D cell proliferation, and supplementation of valine restored mTORC1 activity. Our results show that K562-D cell can be a potent tool for the investigation of PKU at the molecular level and to explore new therapeutic approaches to the disease.

Phenylpyruvic acid (PPA) is an alpha keto acid, which has the potential to be used in monogastric animals' diets to prevent excessive nitrogen accumulation in their manure and adverse effects on the environment. PPA is also used as a flavor enhancer in the food industry and for kidney patients' diets to decrease urea accumulation in the body. However, the high production cost of PPA is limiting the use for these applications. Therefore, this project was undertaken to enhance PPA production by submerged fermentation. Firstly, microorganism selection was performed and Proteus vulgaris was determined to be the best strain for PPA production among four evaluated. Growth parameters (temperature, pH, and aeration) and concentrations of medium ingredients (glucose, yeast extract, and phenylalanine) were optimized in 2-L bioreactors by using a Box-Behnken design. The optimum temperature, pH, and aeration levels were determined to be 34.5oC, 5.12, and 0.5 vvm, respectively. Concentrations for optimizing the fermentation medium for glucose, yeast extract, and phenylalanine were 119, 3.68 , and 14.84 g/L, respectively. Under these optimum conditions, 1349 mg/L PPA was produced by Proteus vulgaris in submerged fermentation. This study demonstrated about a 3-fold improvement compared to shake flask fermentation (358 mg/L PPA).

Alpha keto acids are deaminated forms of amino acids that have received significant attention as feed and food additives in the agriculture and medical industries. To date, their production has been commonly performed at shake-flask scale with low product concentrations. In this study, production of phenylpyruvic acid (PPA), which is the alpha keto acid of phenylalanine was investigated. First, various microorganisms were screened to select the most efficient producer. Thereafter, growth parameters (temperature, pH, and aeration) were optimized in bench scale bioreactors to maximize both PPA and biomass concentration in bench scale bioreactors, using response surface methodology. Among the four different microorganisms evaluated, Proteus vulgaris was the most productive strain for PPA production. Optimum temperature, pH, and aeration conditions were determined as 34.5 A degrees C, 5.12, and 0.5 vvm for PPA production, whereas 36.9 A degrees C, pH 6.87, and 0.96 vvm for the biomass production. Under these optimum conditions, PPA concentration was enhanced to 1,054 mg/L, which was almost three times higher than shake-flask fermentation concentrations. Moreover, P. vulgaris biomass was produced at 3.25 g/L under optimum conditions. Overall, this study demonstrated that optimization of growth parameters improved PPA production in 1-L working volume bench-scale bioreactors compared to previous studies in the literature and was a first step to scale up the production to industrial production.

A UV-guided fractionation of the AcOEt extract of the fermentation broth of Guignardia sp., an endophytic fungus from the leaves of the tropical tree Spondias mombin, resulted in the identification of the new metabolite (−)-(2S,5Z)-2-(1-methylethyl)-4-oxo-5-(phenylmethylene)-1,3-dioxolane-2-carboxylic acid (1), isolated as NH salt 1a. The metabolite 1 was designated (−)-(S)-guignardic acid. This first member of a new class of natural compounds contains a dioxolanone moiety formed by fusion of 2-oxo-3-phenylpropanoic acid (phenylpyruvic acid) and 3-methyl-2-oxobutanoic acid (dimethylpyruvic acid), products of the oxidative deamination of phenylalanine and valine, respectively. The structure of 1a was deduced from spectral data (UV, IR, MS, 1H- and 13C-NMR) and confirmed by asymmetric synthesis.

l -Amino acid deaminase ( l -AAD) from Proteus myxofaciens was cloned and over-expressed in Escherichia coli K12. This enzyme has a broad substrate specificity, working on both natural and unnatural l -amino acids. Of the 20 naturally occurring l -amino acids, l -AAD prefers amino acid substrates that have aliphatic, aromatic or sulfur-containing side chains; those with charged side chains (–CO2− or –NH3+) are poor or non-substrates. Enzyme activity was monitored using a microtiter-plate-based assay, which measures the formation of phenylpyruvic acid from l -phenylalanine. The reaction has an absolute requirement for O2, releases NH3 and does not produce H2O2. Substrate comparisons were carried out by using an O2 electrode to measure the O2 utilization rates. Studies on partially purified enzyme show a pH optimum of 7.5 with a subunit molecular weight of approximately 51 kDa. Additional purification and characterization strategies will be presented. The use of whole cells containing l -AAD will be discussed to prepare chiral pharmaceutical intermediates.

The production of 4-hydroxyphenyllactic acid (4-HO-PLA), a novel antifungal compound, was studied in Lactobacillus sp. SK007 growth. When grown in MRS broth, the strain could produce 75 microg/ml HO-4-PLA, which was the highest reported so far. Tyrosine and 4-hydroxyphenylpyruvic acid (HO-4-PPA) supplements during fermentation could both increase the HO-4-PLA production yield, and the effect of HO-4-PPA on HO-4-PLA production was remarkably better than that of tyrosine. Using HO-4-PPA as substrate could effectively produce HO-4-PLA, which reached 1.26 mg/ml.

Synthesis of a substituted phenylpyruvic acid was carried out at 60 °C and 3.0MPa using cobalt pyridine-2-carboxylate as a catalyst for the double carbonylation of benzyl chloride.

The synthesis of a tautomeric keto/enol mixture of o-nitrophenylpyruvic acid followed the acid hydrolysis of the azlactone of o-nitrobenzaldehyde was carried out. The structures of the two tautomeric forms were assigned by NMR spectroscopy. X-ray diffraction of a single crystal revealed that the crystalline form corresponds to the keto tautomer. Quantum mechanics calculations in the gas phase confirmed the experimental findings in solution.

The condensation of substituted 2-benzyl-4-hydrazinopyrimidines with phenylpyruvic acid gave the corresponding hydrazones, which cyclize upon the action of POCl, to give derivatives of pyrimido[6,1-c][1,2,4]-triazine. The substituted 2-benzylpyrimidinylhydrazides of some carboxylic acids react with POCl, to give 1,2,4-triazolo[4,3-c]pyrimidines. The reaction of 7-benzyl-5-methyl-l-phenyl-1,2,4-triazolo[2,3-c]pyrimidine with sodium ethylate leads to rearrangement and formation of 7-benzyl-5-methyl-2-phenyl-1,2,4-triazolo[2,3-c]pyrimidine.

Polymorphs I and II of phenylpyruvic acid are obtained as mixtures of both crystal forms or relatively pure crystals, from different solvents. Polymorph I is more stable than polymorph II at room temperature. Spectral characteristics of these polymorphs are discussed on the basis of IR, Raman and solid state 13 C NMR spectra. Also, the assignment of the IR features observed in the 1600–1700 cm −1 region is re-investigated by referring to the spectra of heavy-atom substituted derivatives. It is suggested that the CO stretching band is split by the crystal field for both polymorphs.

Cells obtained from growth of Achromobacter eurydice , Pseudomonas aromatica and Pseudomonas putida on l -phenylalanine containing medium catalyzed the enzymatic acyloin condensation of phenylpyruvic acid 1 and acetaldehyde 2 by phenylpyruvate decarboxylase to produce 3-hydroxy-1-phenyl-2-butanone 3 . The acyloin condensation by Achromobacter eurydice and P. aromatica was stereoselective, providing the 3 R enantiomer 3a with enantiomeric excess (ee) of 95% and 84%, respectively. A partially purified enzyme was prepared from the cell free extract of Achromobacter eurydice. The acyloin product 3a was obtained in 45% yield with an ee of 91% by using this partially purified preparation of phenylpyruvate decarboxylase.

The preparation of phenylalanine from phenylpyruvic acid by amination and hydrogenation was investigated over amorphous Ni–B alloy catalysts prepared by chemical reduction. The amorphous Ni–B alloy showed better activity and selectivity than the commercial Raney Ni and Urushibara Ni catalysts. After the Ni–B alloy was supported on SiO 2 , the activity and selectivity of Ni–B/SiO 2 were further improved to 97.67%. The higher activity and selectivity of the amorphous alloy catalysts were mainly ascribed to the electron-rich Ni due to electron donation from B and the larger specific surface area of the amorphous alloys.

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.

We have studied the production of phenylpyruvic acid by mild stereospecific oxidation of d-phenylalanine (from d/l racemic mixtures) catalyzed by d-amino acid oxidase (DAAO) from Trigonopsis variabilis. The performance of this reaction requires the continuous bubbling of oxygen that inactivated soluble DAAO. The immobilization of the enzyme inside porous supports avoids the interaction of the enzyme with the hydrophobic oxygen/water interfaces; therefore, this inactivation cause is fully prevented. Hydrogen peroxide (a reaction by-product) exerts deleterious effects on both the enzyme and the desired product (phenylpyruvic acid). These deleterious effects could be reduced by using immobilized DAAO and separately immobilized catalase; however, a much more effective elimination of hydrogen peroxide was achieved when both enzymes were coimmobilized. The effectiveness of coimmobilized catalase in preventing phenylpyruvic destruction by hydrogen peroxide is more than 20-fold higher than that of separately immobilized catalase. In fact, by using DAAO/catalase-coimmobilized derivatives, more than 98% of phenylpyruvic acid was obtained after complete oxidation of d-phenylalanine by using the racemic mixture as substrate. This also prevented enzyme from inactivation. In this way, 40 reaction cycles were performed without apparent loss of enzyme activity. These results open an effective and simple way of using any oxidase where we can expect very similar problems to those described in this paper.

Keto-enol tautomerism of mono-substituted phenylpyruvic acids has been studied by the 1H and 13C NMR spectra. The equilibrium constants and the kinetic parameters for the tautomerism were obtained from the spectral data. The equilibrium constants are strongly dependent on the position of the substitution; the values for the o-substituted PPAs are several times greater than those of the m- or p-substituted derivatives. The PM3 calculations have been carried out to obtain the information on the preferred conformations of the tautomers and on the mechanism for the tautomerism. The results suggest the involvement of a solvent molecule in the equilibrium process.

The NAD+-dependent phenylalanine dehydrogenase from Nocardia sp239 has been crystallized by the hanging-drop method of vapour diffusion using ammonium sulfate as the precipitant. Two crystal forms were obtained in the presence and absence of the enzyme substrates phenylpyruvic acid or phenylalanine and its coenzyme NADH. Crystals of the native protein belong to the hexagonal system, with the space group being one of the enantiomorphic pair P6122 or P6522. The cell dimensions are a = b = 111.0, c = 174.5 A, alpha = beta = 90 and gamma = 120 degrees. Crystals grown from the protein co-crystallized with its substrates all belong to the trigonal system, space group P3121 or P3221, with unit-cell dimensions of a = b = 88.1, c = 112.6 A, alpha = beta = 90 and gamma = 120 degrees. Preliminary protein-sequencing experiments have established that this enzyme is related to the octameric PheDH's which are members of the wider superfamily of amino-acid dehydrogenases. However, gel-filtration studies suggest that this enzyme is active as a monomer. The full determination of the three-dimensional structure of this phenylalanine dehydrogenase will add to the understanding of the molecular basis of the differential substrate specificity within this enzyme superfamily. In turn this will contribute to the rational design of an amino-acid dehydrogenase which could be used for the diagnosis of phenylketonuria and for the chiral synthesis of high-value pharmaceuticals.

An in vitro study was conducted to examine the effects of salinomycin (SL) and vitamin B(6) (B(6)) on the production of phenylalanine (Phe) from phenylpyruvic acid (PPY) and phenylacetic acid (PAA) and of PAA from Phe and PPY by mixed rumen bacteria (B), mixed rumen protozoa (P) and their mixture (BP). Rumen microorganisms were collected from fistulated goats fed lucerne cubes (Medicago sativa) and a concentrate mixture (3 : 1) twice a day. Microbial suspensions were anaerobically incubated at 39 degrees C for 12 h. Phe and some other related compounds in both supernatants and microbial hydrolysates of the incubations were analyzed by HPLC. When PPY was used as a substrate, it completely disappeared without additives and converted mainly to Phe and PAA on the average by 396 and 178, 440 and 189, and 439 and 147mgr;M in B, P and BP, respectively, during the 12 h incubation period. The rate of disappearance showed no significant differences between the microbial suspensions with and without SL and B(6) during the incubation period. The production of Phe from PPY with SL was enhanced (p0.05) by 40, 20 and 19% in B, P and BP, respectively, while PAA production from PPY with SL was inhibited (p0.05) by 35, 37 and 38% in B, P and BP, respectively, during the 12 h incubation period. On the other hand, with B(6), the production of Phe and PAA from PPY tended to be enhanced by 14 and 17, 9 and 11, and 7 and 22% in B, P and BP, respectively, during the 12 h incubation period. When PAA added as a substrate was incubated in the incubation medium without any additives, it disappeared by 483, 462 and 507mgr;M and converted mainly to Phe on the average by 231, 244 and 248mgr;M in B, P and BP, respectively. The disappearance of PAA with SL was inhibited (p0.05) by 16, 15 and 20%, in B, P and BP, respectively, whereas the disappearance of PAA with B6 was almost the same as that without B(6) in B and BP suspensions but tended to be enhanced by more than 9% in P suspensions during the 12 h incubation period. The production of Phe from PAA with SL tended to be inhibited by 12, 11 and 8% in B, P and BP, respectively, during the 6 h incubation period, but the inhibition was weakened during the 12 h incubation period, whereas Phe production from PAA with B(6) tended to be enhanced by 13, 16 and 8% in B, P and BP, respectively. When Phe was added as a substrate, the net Phe disappearance without additives was 549, 365 and 842mgr;M and converted mainly to PAA on the average by 254, 205 and 461mgr;M in B, P and BP, respectively. The net disappearance of Phe with SL was inhibited (p0.05) by 38, 28 and 46%, whereas the net disappearance of Phe with B(6) was enhanced (p0.05) by 9, 8 and 7% in B, P and BP, respectively. The production of PAA from Phe with SL was inhibited (p0.05) by 73, 54 and 76% in B, P and BP, respectively. On the other hand, with B(6), PAA production from Phe was enhanced (p0.05) by 19, 18 and 20% in B, P and BP, respectively. Based on these results, it seems that SL inhibited Phe disappearance and enhanced the synthesis of Phe from PPY, though not from PAA, and accumulated free Phe in the medium, whereas B(6) also enhanced Phe synthesis both from PPY and PAA, which could provide additional amino N for animals.

An NAD-dependent d-lactate dehydrogenase (d-nLDH) of Lactobacillus bulgaricus ATCC 11842 was rationally re-designed for asymmetric reduction of a homologous series of α-keto carboxylic acids such as phenylpyruvic acid (PPA), α-ketobutyric acid, α-ketovaleric acid, β-hydroxypyruvate. Compared with wild-type d-nLDH, the Y52L mutant d-nLDH showed elevated activities toward unnatural substrates especially with large substitutes at C-3. By the biocatalysis combined with a formate dehydrogenase for in situ generation of NADH, the corresponding (R)-α-hydroxy carboxylic acids could be produced at high yields and highly optical purities. Taking the production of chiral (R)-phenyllactic acid (PLA) from PPA for example, 50 mM PPA was completely reduced to (R)-PLA in 90 min with a high yield of 99.0% and a highly optical purity (>99.9% e.e.) by the coupling system. The results presented in this work suggest a promising alternative for the production of chiral α-hydroxy carboxylic acids.

3-Phenyllactic acid (PLA) is an antimicrobial compound with broad and effective antimicrobial activity against both bacteria and fungi. Enzymatic production of PLA can be carried out from phenylpyruvic acid by lactate dehydrogenase (LDH); however, the enzymatic reaction is accompanied by NADH oxidation that inhibits PLA biotransformation. Here, NADH regeneration was achieved using the formate dehydrogenase from Ogataea parapolymorpha and introduced into the d-PLA production process using the d-LDH from Pediococcus pentosaceus. Optimum PLA production by dual enzyme treatment was at pH 6.0 and 50 °C with both enzymes at 0.4 μM. Using 0.2 mM NADH, d-PLA production by NADH regeneration system reached 5.5 mM, which was significantly higher than that by a single-enzyme reaction.

Geotrichum candidum ATCC 204307 was previously found to generate phenyllactic acid (PLA) and indoleacetic acid (ILA) in complex culture media. In this study, a relationship between concentrations of PLA, ILA, and hydroxy PLA (OH-PLA) and initial concentrations of phenylalanine, tryptophan, and tyrosine, added respectively as unique sources of nitrogen in synthetic medium, was established. Phenylpyruvic acid (PPA), an intermediate compound of PLA metabolism, was able to induce not only PLA but also phenylethyl alcohol (PEA) production when used separately as initial substrate. Under pH, temperature, and salt concentrations used for cheese-making, phenylalanine was found to be the most efficient substrate for antimicrobial metabolite production. In excess of substrate, different yeast strains of Geotrichum candidum, Yarrowia lipolytica, Candida natalensis, and Candida catenulata were shown here to produce 1.6 0.5–5.0 0.2 mM of PLA from phenylalanine, 5.0 0.1–10.9 0.3 mM of ILA from tryptophan, and 1.3 0.3–7.0 0.02 of PLA and 0.1 0.0–2.22 0.09 mM of PEA from PPA. Geotrichum candidum ATCC 204307 was the highest producer. This is the first time these antimicrobial metabolites PLA, OH-PLA, ILA, and PEA are being reported as the reaction products of aromatic amino acids catabolism in G. candidum. Antilisterial metabolite; Geotrichum candidum

The basidiomycete Ischnoderma benzoinum was submerged cultured for 14 days in a 21 bioreactor. After 4 days of cultivation the growth medium was supplemented with ring [ 2 H] x -labelled l -phenylalanine. The major aromatic catabolites were benzaldehyde and 3-phenylpropanol. Several other aromatic compounds identified labelled pointed to a degradation pathway to benzaldehyde starting with an oxidative deamination of l -phenylalanine to phenylpyruvic acid. Later on, a metabolic shift started to favour a reductive pathway suggesting eliminative deamination of l -phenylalanine and stepwise reduction of cinnamic acid to 3-phenylpropanol.

An enzymatic system for the synthesis of N-methyl- l -phenylalanine from phenylpyruvic acid and methylamine with a novel enzyme, N-methyl- l -amino acid dehydrogenase from Pseudomonas putida ATCC12633, using NADP+ and glucose dehydrogenase from Bacillus subtilis as a co-factor-recycling system is described. Analysis of the product on a laboratory preparative scale process revealed N-methyl- l -phenylalanine in 98% yield and over 99% ee. N-Methyl- l -phenylalanine can be used as chiral building blocks for the synthesis of several products with pharmacological activity.

Phenylacetic acid (PAA) is a deamination product of phenylalanine (PHE) applied to soil, which can have a positive physiological effect on plant growth and development. The objective of this study was to determine the factors limiting deamination of PHE when added to soils, determine the major pathway upon detection of metabolic intermediates, and assess the growth-promoting effect on maize (Zea mays L.) of an exogenous application of PHE to soil. The highest activity of PHE deamination in soils occurred at pH 8.5 and on incubation temperature of 40°C. The soil assay used to determine these parameters was based on the amount of NH 4 -N cleaved from L-PHE when incubated for 48 h in the presence of toluene. A sigmoidal relationship was observed between NH 4 -N and PHE concentration, indicating cooperative kinetics. Both phenylpyruvic acid and PAA were detected by high-performance liquid chromatography (HPLC) following the addition of PHE to soil. A glasshouse experiment revealed that an exogenous application of PHE as a soil drench to established uniform seedlings of maize had a significant effect on vegetative growth parameters (shoot height, shoot fresh weight, internodal distance, uppermost leaf collar base distance, and leaf width). Since PAA is a well-established plant growth regulator, it was concluded that this metabolic product derived from PHE in soil was responsible for the stimulatory growth effects in maize.

Phenylpyruvic acid (PPA) is widely used in the pharmaceutical, food, and chemical industries. Here, a two-step bioconversion process, involving growing and resting cells, was established to produce PPA from l-phenylalanine using the engineered Escherichia coli constructed previously. First, the biotransformation conditions for growing cells were optimized (l-phenylalanine concentration 20.0 g·L-1, temperature 35°C) and a two-stage temperature control strategy (keep 20°C for 12 h and increase the temperature to 35°C until the end of biotransformation) was performed. The biotransformation conditions for resting cells were then optimized in 3-L bioreactor and the optimized conditions were as follows: agitation speed 500 rpm, aeration rate 1.5 vvm, and l-phenylalanine concentration 30 g·L-1. The total maximal production (mass conversion rate) reached 29.8 ± 2.1 g·L-1 (99.3%) and 75.1 ± 2.5 g·L-1 (93.9%) in the flask and 3-L bioreactor, respectively. Finally, a kinetic model was established, and it was revealed that the substrate and product inhibition were the main limiting factors for resting cell biotransformation.

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.

Aroma is an essential factor affecting the quality of tea ( Camellia sinensis ) products. While changes of volatile compounds during tea manufacturing have been intensively studied, the effect of environmental factors on volatile contents of fresh tea leaves has received less attention. We found that C. sinensis var. Yabukita kept in darkness by shading treatment for 3 weeks developed etiolated leaves with significantly increased levels of volatiles, especially volatile phenylpropanoids/benzenoids (VPBs). Upstream metabolites of VPBs, in particular shikimic acid, prephenic acid, and phenylpyruvic acid, showed lower levels in dark treated than in control leaves, whereas the contents of most amino acids including l -phenylalanine, a key precursor of VPBs, were significantly enhanced. In addition, analysis by ultra performance liquid chromatography-time of flight mass spectrometry, capillary electrophoresis–time of flight mass spectrometry, high performance liquid chromatography, and gas chromatography–mass spectrometry indicated that volatile and non-volatile metabolite profiles differed significantly between dark treated and untreated leaves.

In 1934, two severely mentally retarded children were examined by Dr Asbjørn Følling. He proved, by classical organic chemistry, that they excreted phenylpyruvic acid in their urine. The substance was also found in the urine of eight additional mentally retarded patients. Based on these observations, oligophrenia phenylpyrouvica (later termed phenylketonuria) was described as a new inborn error of metabolism. Følling later showed the pattern of an autosomal recessive genetic disease, probably caused by a block in phenylalanine metabolism, and that asymptomatic heterozygote carriers of the trait could be detected by phenylalanine loading. The stepwise elucidation and the line of reasoning are described. Phenylketonuria was the first inborn error of metabolism shown to affect the mind, and its importance as a model disease is emphasized. The article finally gives some insight into aspects of the personality of the discoverer.

The structures and conformation of 3-methoxy-4-hydroxy-5-chloro-phenylpyruvic acid3 and its acetate ester4 have been investigated by X-ray crystallography and by spectroscopic methods. Three independent molecules crystallized for the ester4 with the triclinic symmetry and the centrosymmetric space group (Z=6) and with the cell dimensionsa=11.764(6),b=13.549(5),c=13.978(15) A. α=100.08(7), β=94.62(8), γ=115.06(4)°. The three conformers of4 exist as the enolate tautomers and not the keto form.Trans extended side pyruvic acid side chains were observed for the three conformers. The crystalline cohesion was ensured by a strong network of hydrogen bonds. The NMR spectra of the phenylpyruvic acid3 and the acetate ester4 exhibited each a single proton on the benzylic carbon atom and chemical shift values supporting the existence of the enolate tautomer form for these phenylpyruvic acid compounds in solution.

FT-IR, FT-Raman and High Resolution NMR spectra of 3-phenyl-2-thiopyruvic acid (PTPA) have been measured in solution and in the solid state. Spectral assignments were carried out by referring to data of PTPA derivatives including para-substituted PTPA's, PTPA-d5 and PTPA disulfide. All of the spectral evidences coherently point out that PTPA exists exclusively as the ene-thiol form both in solution and in the solid state. Detailed spectral features of PTPA were discussed in comparison with those of phenylpyruvic acid.

An analytical method which offers accurate determination and identification of eight α-keto acids (α-ketoglutaric acid, pyruvic acid, 4-hydroxyphenylpyruvic acid, 3-methyl-2-oxobutyric acid, α-keto-γ-methylthiobutyric acid, 4-methyl-2-oxovaleric acid, 3-methyl-2-oxovaleric acid, and phenylpyruvic acid) in pork meat and Iberian ham samples is reported. The method utilises a highly selective and sensitive method of multiple reaction monitoring (MRM) by mass spectrometry. The analytical method is simple (although the chemical derivatisation of the α-keto acids with dansylhydrazine is required), precise (18% RSD), accurate (90-110%), sensitive (0.01-0.34 mg/kg of defatted and freeze-dried meat depending on the α-keto acid) and linear (R0.99) over several orders of magnitude (until 0.01-146.1 mg/kg of defatted and freeze-dried meat depending on the α-keto acid). Using this methodology, α-keto acids were found to be present in pork meat to a low extent, and their concentration increased when they were determined in Iberian ham. This is the first report of the presence of α-keto acids in both pork meats and Iberian hams.

Phenylketonuria is a recessive autosomal disorder that is caused by a deficiency in the activity of phenylalanine-4-hydroxylase, which converts phenylalanine to tyrosine, leading to the accumulation of phenylalanine and its metabolites phenyllactic acid, phenylacetic acid, and phenylpyruvic acid in the blood and tissues of patients. Phenylketonuria is characterized by severe neurological symptoms, but the mechanisms underlying brain damage have not been clarified. Recent studies have shown the involvement of oxidative stress in the neuropathology of hyperphenylalaninemia. Glucose-6-phosphate dehydrogenase plays an important role in antioxidant defense because it is the main source of reduced nicotinamide adenine dinucleotide phosphate (NADPH), providing a reducing power that is essential in protecting cells against oxidative stress. Therefore, the present study investigated the in vitro effect of phenylalanine (0.5, 1, 2.5, and 5 mM) and its metabolites phenyllactic acid, phenylacetic acid, and phenylpyruvic acid (0.2, 0.6, and 1.2 mM) on the activity of enzymes of the pentose phosphate pathway, which is involved in the oxidative phase in rat brain homogenates. 6-Phosphogluconate dehydrogenase activity was not altered by any of the substances tested. Phenylalanine, phenyllactic acid, and phenylacetic acid had no effect on glucose-6-phosphate dehydrogenase activity. Phenylpyruvic acid significantly reduced glucose-6-phosphate dehydrogenase activity without pre-incubation and after 1 h of pre-incubation with the homogenates. The inhibition of glucose-6-phosphate dehydrogenase activity caused by phenylpyruvic acid could elicit an impairment of NADPH production and might eventually alter the cellular redox status. The role of phenylpyruvic acid in the pathophysiological mechanisms of phenylketonuria remains unknown.

The gene coding for D-lactate dehydrogenase (D-LDH) from Pediococcus acidilactici DSM 20284 was cloned and expressed in E. coli. The recombinant enzyme was purified by nickel-affinity chromatography. It converted phenylpyruvic acid (PPA) to 3-phenyllactic acid maximally at 30°C and pH 5.5 with a specific activity of 140 and 422 U/mg for PPA and pyruvate, respectively. The K(m), turnover number (k(cat)), and catalytic efficiency (k(cat)/K(m)) for PPA were 2.9 mM, 305 s(-1), and 105 mM(-1) s(-1), respectively.

Background Phenyllactic acid (PLA), a novel antimicrobial compound with broad and effective antimicrobial activity against both bacteria and fungi, can be produced by many microorganisms, especially lactic acid bacteria. However, the concentration and productivity of PLA have been low in previous studies. The enzymes responsible for conversion of phenylpyruvic acid (PPA) into PLA are equivocal. Methodology/Principal Findings A novel thermophilic strain, Bacillus coagulans SDM, was isolated for production of PLA. When the solubility and dissolution rate of PPA were enhanced at a high temperature, whole cells of B. coagulans SDM could effectively convert PPA into PLA at a high concentration (37.3 g l−1) and high productivity (2.3 g l−1 h−1) under optimal conditions. Enzyme activity staining and kinetic studies identified NAD-dependent lactate dehydrogenases as the key enzymes that reduced PPA to PLA. Conclusions/Significance Taking advantage of the thermophilic character of B. coagulans SDM, a high yield and productivity of PLA were obtained. The enzymes involved in PLA production were identified and characterized, which makes possible the rational design and construction of microorganisms suitable for PLA production with metabolic engineering.

The formation and disappearance of acrylamide in binary and ternary mixtures of asparagine (or acrylamide), carbonyl compounds and amino acid derivatives was studied in an attempt to understand the different reactions produced in mixtures of carbonyl compounds and amino acids. The carbonyl compounds assayed included glucose, 2,4-decadienal, mercaptopyruvic acid, phenylpyruvic acid, and phenylacetaldehyde. The assayed amino acids were cysteine, N-acetylcysteine, and phenylalanine, in addition to asparagine. All assayed carbonyl compounds were able to convert asparagine into acrylamide to various extents, and some of them were more reactive than glucose. In addition, they inhibited the Michael additions responsible for acrylamide disappearance. On the other hand, the addition of amino acids mostly resulted in decreases of acrylamide, although acrylamide also increased in some mixtures. Amino acids decreased acrylamide yield because of both their competence with asparagine for carbonyl compounds and their reaction with the produced acrylamide. However, carbonyl-amine reactions formed new carbonyl compounds, which increased acrylamide content. Therefore, asparagine degradation in the presence of amino acids is likely to be a balance between the decrease of degradation produced by the original carbonyl compounds and the increase of degradation due to the carbonyl compounds formed. © 2011 Elsevier Ltd. All rights reserved., This study was supported in part by the European Union (FEDER Funds), the Junta de Andalucía (Project P07-AGR-2846), and the Plan Nacional de I+D of the Ministerio de Ciencia e Innovación of Spain (Project AGL2009-07638).

Phenyl{1- 14 C}alanine {3}, phenyl{2- 14 C}pyruvate {4}, and phenyl{1- 14 C}lactate {5} were fed singly and in competition with unlabeled phenylalanine, phenyllactate, and phenylpyruvate to Datura stramonium. The activities recorded in the alkaloids hyoscyamine {1} and hyoscine (scopolamine) {2} suggested that phenyllactate {5} was the closest precursor for the tropic acid moiety of these alkaloids. Hyoscyamine {1}, from plants fed with phenyl{2- 14 C}pyruvate {5}, was hydrolyzed, but the resultant tropic acid 7 contained only 21% of the activity, the remainder being located in the tropine

Growth promotion and iron transport studies revealed that certain alpha-keto acids generated by amino acid deaminases, by enterobacteria of the Proteus-Providencia-Morganella group (of the tribe Proteeae), show significant siderophore activity. Their iron-binding properties were confirmed by the chrome azurol S assay and UV spectra. These compounds form ligand-to-metal charge transfer bands in the range of 400 to 500 nm. Additional absorption bands of the enolized ligands at 500 to 700 nm are responsible for color formation. Siderophore activity was most pronounced with alpha-keto acids possessing an aromatic or heteroaromatic side chain, like phenylpyruvic acid and indolylpyruvic acid, resulting from deamination of phenylalanine and tryptophan, respectively. In addition, alpha-keto acids possessing longer nonpolar side chains, like alpha-ketoisocaproic acid or alpha-ketoisovaleric acid and even alpha-ketoadipic acid, also showed siderophore activity which was absent or negligible with smaller alpha-keto acids or those possessing polar functional groups, like pyruvic acid, alpha-ketobutyric acid, or alpha-ketoglutaric acid. The fact that deaminase-negative enterobacteria, like Escherichia coli and Salmonella spp., could not utilize alpha-keto acids supports the view that specific iron-carboxylate transport systems have evolved in members of the tribe Proteeae and are designed to recognize ferric complexes of both alpha-hydroxy acids and alpha-keto acids, of which the latter can easily be generated by L-amino acid deaminases in an amino acid-rich medium. Exogenous siderophores, like ferric hydroxamates (ferrichromes) and ferric polycarboxylates (rhizoferrin and citrate), were also utilized by members of the tribe Proteeae.

Nine new bromotyrosine-derived metabolites, purpuramines A∼I( 1∼9 and phenylpyruvic acid oxime ( 10 ) have been isolated from the marine sponge, Psammaplysilla purpurea . Their structures were determined by interpretation of spectral data. Compunds 1∼9 exhibited antibacterial activity against Staphylococcus aureus .

High resolution solid state 13 C NMR measurements were made on phenylpyruvic acid and its sodium, lithium and calcium salts, using the total suppression of spinning side bands and the dipolar diphasing technique. The spectra of their 2- 13 C enriched analogs were also recorded. The NMR data were discussed by reference to the solution spectra, and the following definitive evidence was obtained: the acid, the hydrated sodium and lithium salts and the dehydrated sodium salt take the enol, the diol and the keto form, respectively, but the hydrated calcium salt exists in the keto form. The 13 C NMR signal of the gem -diol carbon was found to appear at 98 ppm. The calcium salt has two doublets at 166 and 134 ppm which originate from the carbons C(1) and C(4); this splitting suggests that the carboxylate group and/or the phenyl ring in the phenylpyruvate anion are oriented in two different ways.

The IR, Raman and NMR spectra of phenylpyruvic acid and its sodium and lithium salts were recorded in aqueous solution. The spectral data indicate that the acid exists mostly in the hydrated keto form (gem-diol form) in acidic solution and that the sodium and lithium salt hydrates take predominantly the normal keto form in aqueous solution in contrast with those in the solid state. Also the solution of the acid and the salts contain a small amount of the enol form. A solvent isotope effect, i.e. the enol content differs between the H2O and D2O solutions of the sodium salt, was found.

The leaves and stems of Aspalathus linearis, a member of the Fabaceae, contains (Z)-2-(β-D-glucopyranosyloxy)-3-phenylpropenoic acid 1, an enolic glucoside of phenylpyruvic acid, representing the first unequivocal evidence for the latter's presence in woody plants. The synthesis of a derivative 2 of the natural product, and of related regiomeric and geometrical isomers 3,4 and 5, and the biosynthetic significance in relation to the shikimic acid pathway are discussed.

A novel method of CE coupled with dual electrochemical detection has been developed for the determination of pathological metabolites of phenylalanine in urine samples. Factors influencing the separation and detection were examined and optimized. Five aromatic acid metabolites and a major coexisting interfering compound uric acid could be well separated within 23 min at a separation voltage of 16 kV using a 35 mmol/L SDS/ 60 mmol/L H 3 BO 3 -Na 2 B 4 O 7 running buffer (pH 8.2). Highly linear response was obtained for these five biomarker compounds over three orders of magnitude with detection limits ranging from 6.6 to 0.064 μg/mL (S/N= 3). The average recovery and RSD were within the range of 92.6―121.0 and 1.0―12.0%, respectively. The proposed method has been used to detect the unconjugated aromatic acids simultaneously in urine samples with the advantages of obtaining more information about target analytes and avoiding redundant measurements and high assay cost, thus could find potential applications involving assays of biomarker compounds for the purpose of fast diagnose of some metabolic diseases including phenylketonuria.