scholarly journals Pectin methylesterase, metal ions and plant cell-wall extension. Hydrolysis of pectin by plant cell-wall pectin methylesterase

1991 ◽  
Vol 279 (2) ◽  
pp. 343-350 ◽  
Author(s):  
J Nari ◽  
G Noat ◽  
J Ricard
Keyword(s):  
Cell Wall ◽  
Metal Ions ◽  
Plant Cell ◽  
Plant Cell Wall ◽  
Direct Interaction ◽  
Enzyme Reaction ◽  
Pectin Methylesterase ◽  
High Concentrations ◽  
Enzyme Molecules ◽  
Hydrolysis Of

The hydrolysis of p-nitrophenyl acetate catalysed by pectin methylesterase is competitively inhibited by pectin and does not require metal ions to occur. The results suggest that the activastion by metal ions may be explained by assuming that they interact with the substrate rather than with the enzyme. With pectin used as substrate, metal ions are required in order to allow the hydrolysis to occur in the presence of pectin methylesterase. This is explained by the existence of ‘blocks’ of carboxy groups on pectin that may trap enzyme molecules and thus prevent the enzyme reaction occurring. Metal ions may interact with these negatively charged groups, thus allowing the enzyme to interact with the ester bonds to be cleaved. At high concentrations, however, metal ions inhibit the enzyme reaction. This is again understandable on the basis of the view that some carboxy groups must be adjacent to the ester bond to be cleaved in order to allow the reaction to proceed. Indeed, if these groups are blocked by metal ions, the enzyme reaction cannot occur, and this is the reason for the apparent inhibition of the reaction by high concentrations of metal ions. Methylene Blue, which may be bound to pectin, may replace metal ions in the ‘activation’ and ‘inhibition’ of the enzyme reaction. A kinetic model based on these results has been proposed and fits the kinetic data very well. All the available results favour the view that metal ions do not affect the reaction through a direct interaction with enzyme, but rather with pectin.

scholarly journals Pectin methylesterase, metal ions and plant cell-wall extension. The role of metal ions in plant cell-wall extension

1991 ◽  
Vol 279 (2) ◽  
pp. 351-354 ◽  
Author(s):  
A M Moustacas ◽  
J Nari ◽  
M Borel ◽  
G Noat ◽  
J Ricard
Keyword(s):  
Cell Wall ◽  
Metal Ions ◽  
Plant Cell ◽  
Electrostatic Potential ◽  
Metal Ion ◽  
Plant Cell Wall ◽  
Pectin Methylesterase ◽  
Ion Concentration ◽  
Cell Wall Extension ◽  
Wall Loosening

The study of pectin methylesterase and wall-loosening enzyme activities in situ, as well as the estimation of the electrostatic potential of the cell wall, suggest a coherent picture of the role played by metal ions and pH in cell-wall extension. Cell-wall growth brings about a decrease of local proton concentration because the electrostatic potential difference (delta psi) of the wall decreases. This in turn activates pectin methylesterase, which restores the initial delta psi value. This process is amplified by the attraction of metal ions in the polyanionic cell-wall matrix. The amplification process is basically due to the release of enzyme molecules that were initially bound to ‘blocks’ of carboxy groups. This increase of metal-ion concentration also results in the activation of wall-loosening enzymes. Moreover, the apparent ‘inhibition’ of pectin methylesterase by high salt concentrations may be considered as a device which prevents the electrostatic potential from becoming too high.

scholarly journals Post-Synthetic Reduction of Pectin Methylesterification Causes Morphological Abnormalities and Alterations to Stress Response in Arabidopsis thaliana

Plants ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 1558
Author(s):  
Nathan T. Reem ◽  
Lauran Chambers ◽  
Ning Zhang ◽  
Siti Farah Abdullah ◽  
Yintong Chen ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Wall ◽  
Plant Cell ◽  
Cell Walls ◽  
Plant Cell Wall ◽  
Normal Growth ◽  
Pectin Methylesterase ◽  
Dwarf Phenotype ◽  
Response To Stress ◽  
Defense Response Genes

Pectin is a critical component of the plant cell wall, supporting wall biomechanics and contributing to cell wall signaling in response to stress. The plant cell carefully regulates pectin methylesterification with endogenous pectin methylesterases (PMEs) and their inhibitors (PMEIs) to promote growth and protect against pathogens. We expressed Aspergillus nidulans pectin methylesterase (AnPME) in Arabidopsis thaliana plants to determine the impacts of methylesterification status on pectin function. Plants expressing AnPME had a roughly 50% reduction in methylester content compared with control plants. AnPME plants displayed a severe dwarf phenotype, including small, bushy rosettes and shorter roots. This phenotype was caused by a reduction in cell elongation. Cell wall composition was altered in AnPME plants, with significantly more arabinose and significantly less galacturonic acid, suggesting that plants actively monitor and compensate for altered pectin content. Cell walls of AnPME plants were more readily degraded by polygalacturonase (PG) alone but were less susceptible to treatment with a mixture of PG and PME. AnPME plants were insensitive to osmotic stress, and their susceptibility to Botrytis cinerea was comparable to wild type plants despite their compromised cell walls. This is likely due to upregulated expression of defense response genes observed in AnPME plants. These results demonstrate the importance of pectin in both normal growth and development, and in response to biotic and abiotic stresses.

Studies on the structure and function cellulases and hemicellulases.

1993 ◽  
Vol 1993 ◽  
pp. 154-154 ◽  
Author(s):  
H.J. Gilbert ◽  
G.P. Hazlewood
Keyword(s):  
Cell Wall ◽  
Plant Cell ◽  
Plant Cell Wall ◽  
Recombinant Dna ◽  
Molecular Architecture ◽  
Large Molecular Weight ◽  
Integral Structures ◽  
And Function ◽  
Hydrolysis Of

Plant structural polysaccharides provide a major source of nutrient for ruminant livestock. These carbohydrates are not degraded by mammalian-derived enzymes, but are hydrolysed by rumen microbial plant cell wall hydrolases. In view of the pivotal role of microbial cellulases and xylanases in ruminant nutrition, there has been considerable interest in these enzymes. In this paper we wish to illustrate how recombinant DNA (rDNA) technology can be utilised to dissect the biochemistry and molecular architecture of these enzymes, and provides us with the opportunity of generating novel cellulases and xylanases with increased capacity to hydrolyse the plant cell wall.In general cellulases and xylanases from anaerobic microbes associate into large molecular weight complexes, whose integral structures are responsible for the efficient hydrolysis of plant structural polysaccharides. The feasibility of altering these complexes, or transferring them to other organisms represents a significant challenge.

scholarly journals Cellulose and lignin colocalization at the plant cell wall surface limits microbial hydrolysis of Populus biomass

2017 ◽  
Vol 19 (9) ◽  
pp. 2275-2285 ◽  
Author(s):  
Alexandru Dumitrache ◽  
Allison Tolbert ◽  
Jace Natzke ◽  
Steven D. Brown ◽  
Brian H. Davison ◽  
...  
Keyword(s):  
Cell Wall ◽  
Plant Cell ◽  
Plant Cell Wall ◽  
Wall Surface ◽  
Microbial Hydrolysis ◽  
Biological Conversion ◽  
Specialty Chemicals ◽  
Hydrolysis Of ◽  
Oligomeric Compounds

Biorefining of plant feedstocks into fuels and specialty chemicals, using biological conversion, requires the solubilization of lignocellulosics into simpler oligomeric compounds.

scholarly journals Fungi isolated from Miscanthus and sugarcane: biomass conversion, fungal enzymes, and hydrolysis of plant cell wall polymers

2015 ◽  
Vol 8 (1) ◽  
pp. 38 ◽  
Author(s):  
Prachand Shrestha ◽  
Ana B Ibáñez ◽  
Stefan Bauer ◽  
Sydney I Glassman ◽  
Timothy M Szaro ◽  
...  
Keyword(s):  
Cell Wall ◽  
Plant Cell ◽  
Plant Cell Wall ◽  
Biomass Conversion ◽  
Fungal Enzymes ◽  
Cell Wall Polymers ◽  
Hydrolysis Of

scholarly journals Characterisation of the Effect of the Spatial Organisation of Hemicellulases on the Hydrolysis of Plant Biomass Polymer

2020 ◽  
Vol 21 (12) ◽  
pp. 4360
Author(s):  
Thomas Enjalbert ◽  
Marion De La Mare ◽  
Pierre Roblin ◽  
Louise Badruna ◽  
Thierry Vernet ◽  
...  
Keyword(s):  
Cell Wall ◽  
Plant Cell ◽  
Plant Cell Wall ◽  
Plant Biomass ◽  
Reducing Sugar ◽  
Intrinsic Activity ◽  
X Rays ◽  
Spatial Organisation ◽  
The Impact ◽  
Hydrolysis Of

Synergism between enzymes is of crucial importance in cell metabolism. This synergism occurs often through a spatial organisation favouring proximity and substrate channelling. In this context, we developed a strategy for evaluating the impact of the geometry between two enzymes involved in nature in the recycling of the carbon derived from plant cell wall polymers. By using an innovative covalent association process using two protein fragments, Jo and In, we produced two bi-modular chimeric complexes connecting a xylanase and a xylosidase, involved in the deconstruction of xylose-based plant cell wall polymer. We first show that the intrinsic activity of the individual enzymes was preserved. Small Angle X-rays Scattering (SAXS) analysis of the complexes highlighted two different spatial organisations in solution, affecting both the distance between the enzymes (53 Å and 28 Å) and the distance between the catalytic pockets (94 Å and 75 Å). Reducing sugar and HPAEC-PAD analysis revealed different behaviour regarding the hydrolysis of Beechwood xylan. After 24 h of hydrolysis, one complex was able to release a higher amount of reducing sugar compare to the free enzymes (i.e., 15,640 and 14,549 µM of equivalent xylose, respectively). However, more interestingly, the two complexes were able to release variable percentages of xylooligosaccharides compared to the free enzymes. The structure of the complexes revealed some putative steric hindrance, which impacted both enzymatic efficiency and the product profile. This report shows that controlling the spatial geometry between two enzymes would help to better investigate synergism effect within complex multi-enzymatic machinery and control the final product.

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