The enzyme does not act on unsubstituted aliphatic or aromatic aldehydes or glucose; NAD+ can replace NADP+, but with lower affinity. The enzyme was initially believed to act on 4-carboxy-2-hydroxy-cis,cis-muconate 6-semialdehyde and produce 4-carboxy-2-hydroxy-cis,cis-muconate . However, later studies showed that the substrate is the hemiacetal form , and the product is 2-oxo-2H-pyran-4,6-dicarboxylate [2,4].
The enzyme does not act on unsubstituted aliphatic or aromatic aldehydes or glucose; NAD+ can replace NADP+, but with lower affinity. The enzyme was initially believed to act on 4-carboxy-2-hydroxy-cis,cis-muconate 6-semialdehyde and produce 4-carboxy-2-hydroxy-cis,cis-muconate [1]. However, later studies showed that the substrate is the hemiacetal form [3], and the product is 2-oxo-2H-pyran-4,6-dicarboxylate [2,4].
following intramolecular dehydrogenation to the lactone 2-pyrone-4,6-dicarboxylic acid, it is not clear whether the lactonization occurs enzymatically or nonenzymatically
the enzyme activity increases in a sigmoidal manner with increasing concentrations, minimum concentration necessary for the increase of enzyme activity is higher than 0.05 mM, effectively eliminates the dye inhibition
in tobacco leaves, transient expression of bacterial feedback-resistant 3-deoxy-D-arabinoheptulosonate 7-phosphate synthase (AroG) and 3-dehydroshikimate dehydratase (QsuB) produces high titers of protocatechuate (PCA), which is in turn efficiently converted into 2-pyrone-4,6-dicarboxylic acid (PDC) upon co-expression of PCA 4,5-dioxygenase (PmdAB) and 4-carboxy-2-hydroxymuconate-6-semialdehyde dehydrogenase (PmdC) derived from Comamonas testosteroni. Stable expression of AroG in Arabidopsis thaliana in a genetic background containing the QsuB gene enhances PCA content in plant biomass, presumably via an increase of the carbon flux through the shikimate pathway. Introducing AroG and the PDC biosynthetic genes (PmdA, PmdB, and PmdC) into the Arabidopsis QsuB background, or introducing the five genes (AroG, QsuB, PmdA, PmdB, and PmdC) stacked on a single construct into wild-type plants, results in PDC titers of about 1% and about 3% dry weight in plant biomass, respectively. Consistent with previous studies of plants expressing QsuB, all PDC producing lines show strong reduction in lignin content in stems. This low lignin trait is accompanied with improvements of biomass saccharification efficiency due to reduced cell wall recalcitrance to enzymatic degradation. Importantly, most transgenic lines show no reduction in biomass yields
in tobacco leaves, transient expression of bacterial feedback-resistant 3-deoxy-D-arabinoheptulosonate 7-phosphate synthase (AroG) and 3-dehydroshikimate dehydratase (QsuB) produces high titers of protocatechuate (PCA), which is in turn efficiently converted into 2-pyrone-4,6-dicarboxylic acid (PDC) upon co-expression of PCA 4,5-dioxygenase (PmdAB) and 4-carboxy-2-hydroxymuconate-6-semialdehyde dehydrogenase (PmdC) derived from Comamonas testosteroni. Stable expression of AroG in Arabidopsis thaliana in a genetic background containing the QsuB gene enhances PCA content in plant biomass, presumably via an increase of the carbon flux through the shikimate pathway. Introducing AroG and the PDC biosynthetic genes (PmdA, PmdB, and PmdC) into the Arabidopsis QsuB background, or introducing the five genes (AroG, QsuB, PmdA, PmdB, and PmdC) stacked on a single construct into wild-type plants, results in PDC titers of about 1% and about 3% dry weight in plant biomass, respectively. Consistent with previous studies of plants expressing QsuB, all PDC producing lines show strong reduction in lignin content in stems. This low lignin trait is accompanied with improvements of biomass saccharification efficiency due to reduced cell wall recalcitrance to enzymatic degradation. Importantly, most transgenic lines show no reduction in biomass yields
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PURIFICATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
from the cell extract of Escherichia coli, using POROS polyethyleneimine anion-exchange chromatography, POROS quaternized PI anion-exchange chromatography and POROS phenylether hydrophobic-interaction chromatography
gene pmdC, transient recombinant expression of the enzyme in Nicotiana benthamiana, coexpression with PmdA and, PmdB from Comamonas testosteroni, stable expression of enzymes PmdA, PmdB, and PmdC from Comamonas testosteroni in Arabidopsis thaliana, coexpression with 3-dehydroshikimate dehydratase (QsuB). The metabolic pathway is implemented in the Arabidopsis thaliana ecotype Columbia plastids to produce 2-pyrone-4,6-dicarboxylic acid (PDC), overview
engineering plants with the proposed de-novo PDC pathway provides an avenue to enrich biomass with a value-added co-product while simultaneously improving biomass quality for the supply of fermentable sugars. Implementing this strategy into bioenergy crops has the potential to support existing microbial fermentation approaches that exploit lignocellulosic biomass feedstocks for PDC production
Genetic and biochemical characterization of 4-carboxy-2-hydroxymuconate-6-semialdehyde dehydrogenase and its role in the protocatechuate 4,5-cleavage pathway in Sphingomonas paucimobilis SYK-6
In-planta production of the biodegradable polyester precursor 2-pyrone-4,6-dicarboxylic acid (PDC) stacking reduced biomass recalcitrance with value-added co-product