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Richard A. Dixon – One of the best experts on this subject based on the ideXlab platform.

  • plant phenylalanine tyrosine ammonia lyases
    Trends in Plant Science, 2020
    Co-Authors: Jaime Barros, Richard A. Dixon
    Abstract:

    Aromatic aminamino acid deaminases are key enzymes mediating carbon flux from primary to secondary metabolism in plants. Recent studies have uncovered a tyrosine ammonia-lyase that contributes to the typical characteristics of grass cell walls and contributes to about 50% of the total lignin synthesized by the plant. Grasses are currently preferred bioenergy feedstocks and lignin is the most important limiting factor in the conversion of plant biomass to liquid biofuels, as well as being an abundant renewable carbon source that can be industrially exploited. Further research on the structure, evolution, regulation, and biological function of functionally distinct AmmoniaLyases has multiple implications for improving the economics of the agri-food and biofuel industries.

  • Role of bifunctional ammonia-lyase in grass cell wall biosynthesis
    Nature Plants, 2016
    Co-Authors: Jaime Barros, Juan C. Serrani-yarce, Fang Chen, David Baxter, Barney J. Venables, Richard A. Dixon
    Abstract:

    Phenylalanine ammonia lyase (PAL) is a key enzyme that connects primary and secondary metabolic pathways. In the grass Brachypodium , one PAL can use tyrosine as a substrate. This bifunctional PTAL enzyme can produce half of the cell wall lignin. L –Phenylalanine ammonia-lyase (PAL) is the first enzyme in the biosynthesis of phenylpropanoid-derived plant compounds such as flavonoids, coumarins and the cell wall polymer lignin. The cell walls of grasses possess higher proportions of syringyl (S)-rich lignins and high levels of esterified coumaric acid compared with those of dicotyledonous plants, and PAL from grasses can also possess tyrosine ammonia-lyase (TAL) activity, the reason for which has remained unclear. Using phylogenetic, transcriptomic and in vitro biochemical analyses, we identified a single homotetrameric bifunctional ammonia-lyase (PTAL) among eight BdPAL enzymes in the model grass species Brachypodium distachyon . ^13C isotope labelling experiments along with BdPTAL1 -downregulation in transgenic plants showed that the TAL activity of BdPTAL1 can provide nearly half of the total lignin deposited in Brachypodium , with a preference for S-lignin and wall-bound coumarate biosynthesis, indicating that PTAL function is linked to the characteristic features of grass cell walls. Furthermore, isotope dilution experiments suggest that the pathways to lignin from L –phenylalanine and L –tyrosine are distinct beyond the formation of 4-coumarate, supporting the organization of lignin synthesis enzymes in one or more metabolons.

Jaime Barros – One of the best experts on this subject based on the ideXlab platform.

  • plant phenylalanine tyrosine ammonia lyases
    Trends in Plant Science, 2020
    Co-Authors: Jaime Barros, Richard A. Dixon
    Abstract:

    Aromatic amino acid deaminases are key enzymes mediating carbon flux from primary to secondary metabolism in plants. Recent studies have uncovered a tyrosine ammonia-lyase that contributes to the typical characteristics of grass cell walls and contributes to about 50% of the total lignin synthesized by the plant. Grasses are currently preferred bioenergy feedstocks and lignin is the most important limiting factor in the conversion of plant biomass to liquid biofuels, as well as being an abundant renewable carbon source that can be industrially exploited. Further research on the structure, evolution, regulation, and biological function of functionally distinct Ammonia-Lyases has multiple implications for improving the economics of the agri-food and biofuel industries.

  • Role of bifunctional ammonia-lyase in grass cell wall biosynthesis
    Nature Plants, 2016
    Co-Authors: Jaime Barros, Juan C. Serrani-yarce, Fang Chen, David Baxter, Barney J. Venables, Richard A. Dixon
    Abstract:

    Phenylalanine ammonia lyase (PAL) is a key enzyme that connects primary and secondary metabolic pathways. In the grass Brachypodium , one PAL can use tyrosine as a substrate. This bifunctional PTAL enzyme can produce half of the cell wall lignin. L -Phenylalanine ammonia-lyase (PAL) is the first enzyme in the biosynthesis of phenylpropanoid-derived plant compounds such as flavonoids, coumarins and the cell wall polymer lignin. The cell walls of grasses possess higher proportions of syringyl (S)-rich lignins and high levels of esterified coumaric acid compared with those of dicotyledonous plants, and PAL from grasses can also possess tyrosine ammonia-lyase (TAL) activity, the reason for which has remained unclear. Using phylogenetic, transcriptomic and in vitro biochemical analyses, we identified a single homotetrameric bifunctional ammonia-lyase (PTAL) among eight BdPAL enzymes in the model grass species Brachypodium distachyon . ^13C isotope labelling experiments along with BdPTAL1 -downregulation in transgenic plants showed that the TAL activity of BdPTAL1 can provide nearly half of the total lignin deposited in Brachypodium , with a preference for S-lignin and wall-bound coumarate biosynthesis, indicating that PTAL function is linked to the characteristic features of grass cell walls. Furthermore, isotope dilution experiments suggest that the pathways to lignin from L -phenylalanine and L -tyrosine are distinct beyond the formation of 4-coumarate, supporting the organization of lignin synthesis enzymes in one or more metabolons.

Reijo Karjalainen – One of the best experts on this subject based on the ideXlab platform.

  • Elicitor-induced changes of phenylalanine ammonia-lyase activity in barley cell suspension cultures
    Plant Cell Tissue and Organ Culture, 1997
    Co-Authors: Sari Peltonen, Leena Mannonen, Reijo Karjalainen
    Abstract:

    Suspension-cultured barley cells responded to treatments with crude yeast extract and purified glucan preparation by rapidly and transiently (4 h postelicitation) inducing L-phenylalanine ammonia-lyase activity. Similarly, treatment of cell cultures with chitosan resulted in increased phenylalanine ammonia-lyase activity 2–4 h after elicitation, whereas a mycelium preparation of a fungal pathogen, Bipolaris sorokiniana, and purified chitin caused a more delayed induction of phenylalanine ammonia-lyase (8 h postelicitation). The most abundant of the plant cell wall degrading enzymes produced by Bipolaris sorokiniana, β-1,4-xylanase, had only a weak elicitor activity in barley cells suggesting that fungal cellcell wall components rather than the hydrolytic enzymes secreted by the fungus function as recognizable components that cause barley cells to induce defences. Treatment of the elicited cells with a phenylalanine ammonialyase inhiinhibitor, α-aminooxy-β-phenylpropionic acid, resulted in the superinduction of the enzyme indicating the blocking of the feedback regulation mechanisms, whereas in the presence of 1 mM trans-cinnamic acid the elicitor-induction of phenylalanine ammonia-lyase was completely inhibited. Elicitor treatments increased the accumulation of wall-bound phenolics as evidenced by phloroglucinol-HCl staining and thioglycolic acid methods. However, α-aminooxy-β-phenylpropionic acid applied in combination with the elicitor did not prevent the accumulation of phenolics in barley cell walls. This suggested that phenylalanine ammonia-lyase might not play an important role in the synthesis wall-bound phenolic compounds in barley. However, cinnamic acid, whether applied alone or together with the elicitor, increased the amount of wall-bound phenolics in suspension-cultured barley cells.

G. K. Y. Limsowtin – One of the best experts on this subject based on the ideXlab platform.

  • Purification and Characterization of Cystathionine (gamma)-Lyase from Lactococcus lactis subsp. cremoris SK11: Possible Role in Flavor Compound Formation during Cheese Maturation.
    Applied and environmental microbiology, 1997
    Co-Authors: P. G. Bruinenberg, G. De Roo, G. K. Y. Limsowtin
    Abstract:

    A cystathionine (gamma)-lyase (EC 4.4.1.1) ((gamma)-CTL) was purified to homogeneity from a crude cell extract of Lactococcus lactis subsp. cremoris SK11 by a procedure including anion-exchexchange chrochromatography, hydrophobic interaction chrochromatography, and gel filtfiltration chromatography. The activity of SK11 (gamma)-CTL is pyridoxal-5(prm1)-phosphate dependent, and the enzyme catalyzes the (alpha),(gamma)-elimination reaction of L-cystathionine to produce L-cysteine, (alpha)-ketobutyrate, and ammonia. The native enzyme has a molecular mass of approximately 120 to 200 kDa and apparently consists of at least six identical subunits of 20 kDa. In this respect, the SK11 enzyme clearly differs from other bacterial cystathionine lyases, which are all tetrameric proteins with identical subunits of approximately 40 kDa. In addition, the specific activity of purified SK11 (gamma)-CTL toward L-cystathionine is relatively low compared with those reported for other bacterial cystathionine lyases. The SK11 enzyme shows a broad substrate specificity. In the case of L-methionine, the action of SK11 (gamma)-CTL results in the formation of methanethiol, a volatile sulfur compound known to be required in flavor development in cheddar cheese. The (alpha),(beta)-elimination reaction of L-cysteine is also efficiently catalyzed by the enzyme, resulting in the formation of hydrogen sulfide. Although the conditions are far from optimal, cystathionine (gamma)-lyase is still active under cheddar cheese-ripening conditions, namely, pH 5.0 to 5.4 and 5% (wt/vol) NaCl. The possible role of the enzyme in cheese flavor development is discussed.

Kevin T Watts – One of the best experts on this subject based on the ideXlab platform.

  • discovery of a substrate selectivity switch in tyrosine ammonia lyase a member of the aromatic amino acid lyase family
    Chemistry & Biology, 2006
    Co-Authors: Kevin T Watts, Benjamin N Mijts, Andrew J Manning, Claudia Schmidtdannert
    Abstract:

    Tyrosine ammonia-lyase (TAL) is a recently described member of the aromatic aminamino acid lyase family, which also includes phenylalanine (PAL) and histidine AmmoniaLyases (HAL). TAL is highly selective for L-tyrotyrosine, and synthesizes 4-coumcoumaric acid as a protein cofactor or antibiotic precursor in microorganisms. In this report, we identify a single active site residue important for substrate selection in this enzyme family. Replacing the active site residue His89 with Phe in TAL completely switched its substrate selectivity from tyrosine to phenylalanine, thereby converting it into a highly active PAL. When a corresponding mutation was made in PAL, the enzyme lost PAL activity and gained TAL activity. The discovered substrate selectivity switch is a rare example of a complete alteration of substrate specificity by a single point mutation. We also show that the identity of the amino acid at the switch position can serve as a guide to predict substrate specificities of annotated aromatic aminamino acid lyases in genome sequences.

  • Exploring Recombinant Flavonoid Biosynthesis in Metabolically Engineered Escherichia coli
    Chembiochem : a European journal of chemical biology, 2004
    Co-Authors: Kevin T Watts, Pyung Cheon Lee, Claudia Schmidt-dannert
    Abstract:

    Flavonoids are important plant-specific secondary metabolites synthesized from 4-coumaroyl coenzyme A (CoA), derived from the general phenylpropanoid pathway, and three malonyl-CoAs. The synthesis involves a plant type III polyketide synthase, chalcone synthase. We report the cloning and coexpression in Escherichia coli of phenylalanine ammonia lyase, cinnamate-4-hydroxylase, 4-coumarate:CoA ligase, and chalcone synthase from the model plant Arabidopsis thaliana. Simultaneous expression of all four genes resulted in a blockage after the first enzymatic step caused by the presence of nonfunctional cinnamate-4-hydroxylase. To overcome this problem we fed exogenous 4-coumcoumaric acid to induced cultures. We observed high-level production of the flavanone naringenin as a result. We were also able to produce phloretin by feeding cultures with 3-(4-hydroxyphenyl)propionic acid. Feeding with ferulic or caffeic acid did not yield the corresponding flavanones. We have also cloned and partially characterized a new tyrosine ammonia lyase from Rhodobacter sphaeroides. Tyrosine ammonia lyase was substituted for phenylalanine ammonia lyase and cinnamate-4-hydroxylase in our E. coli clones and three different growth media were tested. After 48 h induction, high-level production (20.8 mg L(-1)) of naringenin in metabolically engineered E. coli was observed for the first time.