Reactions of partially purified tyrosine phenol lyase with threonine and other amino acids

Both enantiomers of threonine are transformed to α-ketobutyrate with a partially purified preparation of tyrosine phenol lyase from the cells of Escherichia intermedia A-21. Allothreonine does not undergo the same reaction but is, instead, converted to glycine. The action of tyrosine phenol lyase on a number of other α-amino acids was also studied. The inversion of configuration at C-2 due to the exchange of the α-proton is not a general phenomenon. The mechanism of action of tyrosine phenol lyase on d-amino acids is discussed.     

Synthesis of tyrosine and 3,4-dihydroxyphenylalanine by bacteria Citrobacter freundii

Among facultative-anaerobic bacteria utilizing formic acid, a large number of strains having tyrosine phenol lyase were found. The enzyme can catalyze synthesis of tyrosine and 3,4-dihydroxy phenyl alanine (DOPA) from pyruvate, ammonium and, accordingly, phenol and pyrocatechol. These strains were identified as Citrobacter freundii. Cell suspensions of the most active strains synthesized up to 75 g/l tyrosine for 12 hr, up to 86 g/l tyrosine for 24 hr, and up to 29 g/l DOPA for 42 hr. A medium containing yeast autolysate grown on hydrocarbons can be recommended to produce cells having a high tyrosine phenol lyase activity.     

Formation of tyrosine from glycine, formaldehyde and phenol under the action of a partially purified preparation of tyrosine phenol lyase: The participation of a different enzyme

In the presence of a partially purified preparation of tyrosine phenol lyase, tyrosine is formed in solutions containing glycine, formaldehyde and phenol. The enzyme preparation also catalysed the splitting of allothreonine to glycine and acetaldehyde. An enzyme which is different from tyrosine phenol lyase was shown to be responsible for this aldolase reaction. When an enzyme preparation with a higher specific activity of tyrosine phenol lyase, but without aldolase activity, was used the formation of tyrosine from glycine, formaldehyde and phenol was not observed. It is assumed that the first stage of the process is the formation of serine from glycine and formaldehyde catalysed by the enzyme responsible for the aldolase reaction. Serine in its turn is converted to tyrosine by tyrosine phenol lyase.     

Activities of enzymes involved in amino-acid metabolism in developing rat placenta

Aspartate transaminase, alanine transaminase, glutamate dehydrogenase, arginase, serine dehydratase, tyrosine transaminase, glutamine synthetase, glutaminase and adenylate deaminase activities were measured in crude homogenates of 12, 19 and 21-day rat placentae. There is a considerable quantitative importance in enzymes able to produce free ammonia, such as adenylate deaminase and glutamate dehydrogenase, activity that progressively decrease with the age of placenta. The glutamine synthetase and tyrosine transaminase activities increase with age, while serine dehydratase decreases considerably and aspartate and alanine transaminase do not change practically. Arginase shows a maximum at 19, with lower 12 and 21-day activities. No measurable glutaminase activity has been found. The possible implications of the enzymes studied upon the ammonia-producing activity of rat placenta are discussed together with the relative decreasing role of placenta for the overall metabolic activity of the foetus, especially during the last phases of its development.     

A novel C–S lyase from the latex-producing plant Taraxacum brevicorniculatum displays alanine aminotransferase and l-cystine lyase activity

We isolated a novel pyridoxal-5-phosphate-dependent l-cystine lyase from the dandelion Taraxacum brevicorniculatum. Real time qPCR analysis showed that C–S lyase from Taraxacum brevicorniculatum (TbCSL) mRNA is expressed in all plant tissues, although at relatively low levels in the latex and pedicel. The 1251 bp TbCSL cDNA encodes a protein with a calculated molecular mass of 46,127 kDa. It is homologous to tyrosine and alanine aminotransferases (AlaATs) as well as to an Arabidopsis thaliana carbon–sulfur lyase (C–S lyase) (SUR1), which has a role in glucosinolate metabolism. TbCSL displayed in vitrol-cystine lyase and AlaAT activities of 4 and 19 nkat mg⁻¹ protein, respectively. However, we detected no in vitro tyrosine aminotransferase (TyrAT) activity and RNAi knockdown of the enzyme had no effect on phenotype, showing that TbCSL substrates might be channeled into redundant pathways. TbCSL is in vivo localized in the cytosol and functions as a C–S lyase or an aminotransferase in planta, but the purified enzyme converts at least two substrates specifically, and can thus be utilized for further in vitro applications.     

Enzymes Involved in Anaerobic Polyethylene Glycol Degradation by Pelobacter venetianus and Bacteroides Strain PG1

In extracts of polyethylene glycol (PEG)-grown cells of the strictly anaerobically fermenting bacterium Pelobacter venetianus, two different enzyme activities were detected, a diol dehydratase and a PEG-degrading enzyme which was characterized as a PEG acetaldehyde lyase. Both enzymes were oxygen sensitive and depended on a reductant, such as titanium citrate or sulfhydryl compounds, for optimal activity. The diol dehydratase was inhibited by various corrinoids (adenosylcobalamin, cyanocobalamin, hydroxocobalamin, and methylcobalamin) by up to 37% at a concentration of 100 μM. Changes in ionic strength and the K⁺ ion concentration had only limited effects on this enzyme activity; glycerol inhibited the enzyme by 95%. The PEG-degrading enzyme activity was stimulated by the same corrinoids by up to 80%, exhibited optimal activity in 0.75 M potassium phosphate buffer or in the presence of 4 M KCI, and was only slightly affected by glycerol. Both enzymes were located in the cytoplasmic space. Also, another PEG-degrading bacterium, Bacteroides strain PG1, contained a PEG acetaldehyde lyase activity analogous to the corresponding enzyme of P. venetianus but no diol dehydratase. Our results confirm that corrinoid-influenced PEG degradation analogous to a diol dehydratase reaction is a common strategy among several different strictly anaerobic PEG-degrading bacteria.     

Catalytic properties of extracts from tyrosine phenol lyase producing cells of Escherichia intermedia: Multienzyme complex instead of the single multisubstrate enzyme

Kinetic parameters for the formation of pyruvate from L-tyrosine catalysed by the cell extract of Escherichia intermedia A-21 differ markedly from the parameters of crystalline tyrosine phenol lyase taken from the literature. The substrate specificity of the enzyme in the cell extract was also found to be different from that in the crystalline state. The cell extracts did not show any activity with respect to D-tyrosine, while the reactions with L-and D-enantiomers of serine were brought about mainly by active sites which differ kinetically from the active site responsible for the main reaction. The ratio of activities with respect to L-tyrosine, L-serine and D-serine varied widely depending on the composition of the medium on which the cells had been grown. The high activity of the preparation with respect to L-tyrosine is not a sufficient condition for successful tyrosine synthesis from dl-serine. High activities towards serine enantiomers are also necessary.     

Isolation and properties of tyrosine phenol-lyase from Citrobacter intermedius

A method for preparation of homogeneous tyrosine phenol lyase (EC 4.199.2) from Citrobacter intermedius has been developed. The cells were cultivated in the media with a view to obtain a cell culture with a high activity of tyrosine phenol lyase. The isoelectric point for the enzyme lies at pH 4.9. Tyrosine phenol lyase is strictly stereospecific: it catalyzes the formation of pyruvate only from L-tyrosine, but not from D-tyrosine. Kinetic studies showed that K+ and NH4+ cations are non-competitive activators of the enzyme (Ka = 3.57 X 10(-3) and 1.34 X 10(-4) M, respectively).     

Optimization of process parameters for the production of tyrosine phenol lyase by Citrobacterfreundii MTCC 2424

The process optimization using technological combinations for the production of tyrosine phenol lyase by Citrobacter freundii MTCC 2424 has been carried out in this study. The maximum production of tyrosine phenol lyase (0.15 U) was obtained by culturing C. freundii MTCC 2424 in a medium containing (g/l) meat extract 5.0, yeast extract 5.0, peptone 2.5, and l-tyrosine 1.0 at 25 degrees C for 16 h in a temperature controlled orbital shaker. A 2.5-fold increase in enzyme activity with 1.3-fold decrease in the cost of enzyme production (in terms of media components) was achieved by using different technological combinations. The process optimization using technological combinations allowed quick optimization of large number of variables, which helps in designing of suitable fermentation conditions for the cost-effective production of tyrosine phenol lyase. Moreover, this also provides information for balancing the nutrient concentration with minimum experimentation.     

弗氏柠檬酸细菌酪氨酸酚解酶基因在大肠杆菌中的克隆与表达

以基因组DNA为模板,利用PCR技术从弗氏柠檬酸细菌（Citrobacter freundii)中扩增得到含有酪氨酸酚解酶基因的DNA片段,定向连续到质粒pUC118上,得到重组质粒pTPL,将此重组质粒转化到受体菌E.colXL-1-Blue MRF′中,通过蓝白斑鉴定挑出阳性菌株。从此阳性菌株中提取质粒pTPL并将此质粒转入到E.coliJM109中,用E.coliJM109（pTPL)制备高活性的酪氨酸酚解酶。对质粒稳定性的研究表明,E.coliJM109（pTPL)在无选择压力下37℃连续培养50代以上,质粒丢失率仅有15％,说明质粒基本稳定。     

Redesign of MST enzymes to target lyase activity instead promotes mutase and dehydratase activities

The isochorismate and salicylate synthases are members of the MST family of enzymes. The isochorismate synthases establish an equilibrium for the conversion chorismate to isochorismate and the reverse reaction. The salicylate synthases convert chorismate to salicylate with an isochorismate intermediate; therefore, the salicylate synthases perform isochorismate synthase and isochorismate-pyruvate lyase activities sequentially. While the active site residues are highly conserved, there are two sites that show trends for lyase-activity and lyase-deficiency. Using steady state kinetics and HPLC progress curves, we tested the “interchange” hypothesis that interconversion of the amino acids at these sites would promote lyase activity in the isochorismate synthases and remove lyase activity from the salicylate synthases. An alternative, “permute” hypothesis, that chorismate-utilizing enzymes are designed to permute the substrate into a variety of products and tampering with the active site may lead to identification of adventitious activities, is tested by more sensitive NMR time course experiments. The latter hypothesis held true. The variant enzymes predominantly catalyzed chorismate mutase–prephenate dehydratase activities, sequentially generating prephenate and phenylpyruvate, augmenting previously debated (mutase) or undocumented (dehydratase) adventitious activities.     

Isolation and Characterization of Cell Lines Resistant to Crude Culture Filtrate of Fusarium in Chickpea

Cell lines resistant to Fusarium oxysporum f. sp. Ciceri crude culture filtrate have been selected In Cicer arietinum cv C235. Phenol content and the activities of tyrosine ammonia lyase (TAL), phenylalanine ammonia lyase (PAL) and ß-1, 3-glucanase were Increased by the elicitor In callus cultures of Fusarium susceptible cultlvar C235, resistant cultlvar WR315 and a stable Fusarium resistant cell clone FC-3. The Increase In phenols and glucanase activity, was more In selected cell line than In ev C235 and ev WR315, while the increase In activities of TAL and PAL showed reverse correlation.     

Tyrosine and Phenylalanine Ammonia Lyase Activities during Shoot Initiation in Tobacco Callus Cultures

Both phenylalanine ammonia lyase and tyrosine ammonia lyase were detected in tobacco (Nicotiana tabacum L. Wisconsin 38) callus. The enzymes were separated from each other by Sephadex G-200 column chromatography. Increased activity of tyrosine ammonia lyase was observed during culture of tobacco callus under shoot-forming conditions, while activity of phenylalanine ammonia lyase increased during culture under non-organ-forming conditions. Confirmation of these findings was obtained by examining the incorporation of [¹⁴C]tyrosine and [¹⁴C]phenylalanine into p-coumarate and trans-cinnamate, respectively.     

A Bifunctional Enzyme in Pseudomonas aeruginosa: a New Pattern in the Organization of Enzymes Concerned with Phenylalanine and Tyrosine Biosynthesis

Two isozymes of chorismate mutase (CA mutase(1) and CA mutase(2)) and two isozymes of prephenate dehydratase (PPA dehydratase(1) and PPA dehydratase(2)) have been found in Pseudomonas aeruginosa. The activities CA mutase(2)-PPA dehydratase(2) catalyzing phenylalanine biosynthesis have been purified almost 40-fold and were found to be associated as a bifunctional enzyme or an enzyme complex. The enzymes specific for tyrosine biosynthesis did not appear to manifest such physical association. Thus, the organization of enzymes concerned with phenylalanine and tyrosine biosynthesis in P. aeruginosa is unique and is unlike most other organisms. Single site mutants have been isolated which have lost both CA mutase(2)-PPA dehydratase(2) activities resulting in a requirement for phenylalanine for growth. Single site revertants of these mutants regained both these activities simultaneously and were able to grow on minimal medium. A mutant, r(6), was also isolated which had normal CA mutase(2) but lacked PPA dehydratase(2) activity.     

The l - and d-threonine dehydratases accompanying l-tyrosine phenol-lyase: selective decomposition of d-threonine in racemic mixture

Low-purity preparations from Escherichia intermedia A-21 and Citrobacter freundii 62 cells producing tyrosine phenol-lyase [l-tyrosine phenol-lyase (deaminating), EC 4.1.99.2] catalyse the decomposition of both threonine enantiomers to α-ketobutyric acid. Reactions with l-threonine and d-threonine are effected by two independent enzymes different from tyrosine phenol-lyase. The enzyme which acts on l-threonine has properties characteristic of biosynthetic threonine dehydratase [l-threonine hydro-lyase (deaminating), EC 4.2.1.16]. l-Isoleucine and dl-allothreonine are inhibitors of this enzyme, permitting a selective inhibition of biosynthetic threonine dehydratase and use of the preparations to act selectively on d-threonine in the racemate.     

Efficient strategies to enhance plasmid stability for fermentation of recombinant Escherichia coli harboring tyrosine phenol lyase

Objective

To solve the bottleneck of plasmid instability during microbial fermentation of l-DOPA with recombinant Escherichia coli expressing heterologous tyrosine phenol lyase.

Results

The tyrosine phenol lyase from Fusobacterium nucleatum was constitutively expressed in E. coli and a fed-batch fermentation process with temperature down-shift cultivation was performed. Efficient strategies including replacing the original ampicillin resistance gene, as well as inserting cer site that is active for resolving plasmid multimers were applied. As a result, the plasmid stability was increased. The co-use of cer site on plasmid and kanamycin in culture medium resulted in proportion of plasmid containing cells maintained at 100% after fermentation for 35 h. The specific activity of tyrosine phenol lyase reached 1493 U/g dcw, while the volumetric activity increased from 2943 to 14,408 U/L for l-DOPA biosynthesis.

Conclusions

The established strategies for plasmid stability is not only promoted the applicability of the recombinant cells for l-DOPA production, but also provides important guidance for industrial fermentation with improved microbial productivity.

     

Process development for efficient biosynthesis of l-DOPA with recombinant Escherichia coli harboring tyrosine phenol lyase from Fusobacterium nucleatum

Bioprocess and Biosystems Engineering - The tyrosine phenol lyase (TPL) catalyzed synthesis of L-DOPA was regarded as one of the most economic route for L-DOPA synthesis. In our previous study, a...     

Production of nitric oxide in host-virus interaction: A case study with a compatible begomovirus-kenaf host-pathosystem

Nitric oxide (NO) plays a key role in plant diseases resistance. Here we have first time demonstrated that begomovirus infection in susceptible H. cannabinus plants, results in elevated NO and reactive nitrogen species production during early infection stage not only in infected leaf but also in root and shoot. Production of NO was further confirmed by oxyhemoglobin assay. Furthermore, we used Phenyl alanine ammonia lyase as marker of pathogenesis related enzyme. In addition evidence for protein tyrosine nitration during the early stage of viral infection clearly showed the involvement of nitrosative stress.Key words: nitric oxide, mesta yellow vein mosaic virus, protein nitration