Catalytic Mechanism and Mode of Action of the Periplasmic Alginate Epimerase AlgG

Wolfram, F.; Kitova, Elena N.; Robinson, Howard; Walvoort, Marthe T. C.; Codée, Jeroen D. C.; Klassen, John S.; Howell, P. Lynne

doi:10.1074/jbc.m113.533158

Cited by 42 publications

(63 citation statements)

References 85 publications

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“…It has further been shown that different R-modules have different binding strength, and that this property influences the degree of processivity displayed by a given epimerase ( Buchinger et al, 2014 ). The structure of P. syringae AlgG was recently published ( Wolfram et al, 2014 ) and AlgG was found to form a long right-handed parallel β-helix similar to that of AlgE4. AlgG was calculated to bind at least nine uronic acid residues.…”

Section: Mannuronan C-5 Epimerasesmentioning

confidence: 93%

“…The overall structure of both AlgG and the A-module of AlgE4 display structural similarities to some pectate- and pectin lyases of the PL1 family. While the negative charge in the Ca 2+ -dependent pectate lyases and AlgE4 is likely to be shielded by bound calcium, the calcium-independent pectin lyases, and AlgG use an arginine residue ( Vitali et al, 1998 ; Wolfram et al, 2014 ).…”

Section: Mannuronan C-5 Epimerasesmentioning

confidence: 99%

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Alginate-modifying enzymes: biological roles and biotechnological uses

Ertesvåg

2015

Front. Microbiol.

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Alginate denotes a group of industrially important 1-4-linked biopolymers composed of the C-5-epimers β-D-mannuronic acid (M) and α-L-guluronic acid (G). The polysaccharide is manufactured from brown algae where it constitutes the main structural cell wall polymer. The physical properties of a given alginate molecule, e.g., gel-strength, water-binding capacity, viscosity and biocompatibility, are determined by polymer length, the relative amount and distribution of G residues and the acetyl content, all of which are controlled by alginate modifying enzymes. Alginate has also been isolated from some bacteria belonging to the genera Pseudomonas and Azotobacter, and bacterially synthesized alginate may be O-acetylated at O-2 and/or O-3. Initially, alginate is synthesized as polymannuronic acid, and some M residues are subsequently epimerized to G residues. In bacteria a mannuronan C-5-epimerase (AlgG) and an alginate acetylase (AlgX) are integral parts of the protein complex necessary for alginate polymerization and export. All alginate-producing bacteria use periplasmic alginate lyases to remove alginate molecules aberrantly released to the periplasm. Alginate lyases are also produced by organisms that utilize alginate as carbon source. Most alginate-producing organisms encode more than one mannuronan C-5 epimerase, each introducing its specific pattern of G residues. Acetylation protects against further epimerization and from most alginate lyases. An enzyme from Pseudomonas syringae with alginate deacetylase activity has been reported. Functional and structural studies reveal that alginate lyases and epimerases have related enzyme mechanisms and catalytic sites. Alginate lyases are now utilized as tools for alginate characterization. Secreted epimerases have been shown to function well in vitro, and have been engineered further in order to obtain enzymes that can provide alginates with new and desired properties for use in medical and pharmaceutical applications.

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Section: Mannuronan C-5 Epimerasesmentioning

confidence: 93%

Section: Mannuronan C-5 Epimerasesmentioning

confidence: 99%

Alginate-modifying enzymes: biological roles and biotechnological uses

Ertesvåg

2015

Front. Microbiol.

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“…After crossing the IM, poly-M is transported through the periplasm, the space between the inner and outer membranes (OM), by a membrane spanning multi-protein machine (Alg44, X, G, K)141617 to the OM protein, AlgE, for secretion181920. In the periplasm, poly-M is modified by O-acetylation (AlgI, J, F and X)212223 and epimerization (AlgG)242526. These modifications add acetyl groups to the C-2 and/or C-3 positions of M residues2122 and convert M residues into G residues2426, respectively.…”

mentioning

confidence: 99%

“…In the periplasm, poly-M is modified by O-acetylation (AlgI, J, F and X)212223 and epimerization (AlgG)242526. These modifications add acetyl groups to the C-2 and/or C-3 positions of M residues2122 and convert M residues into G residues2426, respectively. Both modifications affect polymer composition and its barrier properties against therapeutic intervention and host immunity14272829.…”

mentioning

confidence: 99%

Biological function of a polysaccharide degrading enzyme in the periplasm

Wang

Moradali

Goudarztalejerdi

et al. 2016

Sci Rep

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Carbohydrate polymers are industrially and medically important. For instance, a polysaccharide, alginate (from seaweed), is widely used in food, textile and pharmaceutical industries. Certain bacteria also produce alginate through membrane spanning multi-protein complexes. Using Pseudomonas aeruginosa as a model organism, we investigated the biological function of an alginate degrading enzyme, AlgL, in alginate production and biofilm formation. We showed that AlgL negatively impacts alginate production through its enzymatic activity. We also demonstrated that deletion of AlgL does not interfere with polymer length control, epimerization degree or stability of the biosynthesis complex, arguing that AlgL is a free periplasmic protein dispensable for alginate production. This was further supported by our protein-stability and interaction experiments. Interestingly, over-production of AlgL interfered with polymer length control, suggesting that AlgL could be loosely associated with the biosynthesis complex. In addition, chromosomal expression of algL enhanced alginate O-acetylation; both attachment and dispersal stages of the bacterial biofilm lifecycle were sensitive to the level of O-acetylation. Since this modification also protects the pathogen against host defences and enhances other virulence factors, chromosomal expression of algL could be important for the pathogenicity of this organism. Overall, this work improves our understanding of bacterial alginate production and provides new knowledge for alginate production and disease control.

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“…As the polymer passages through the periplasm, 22–44% of β ‐1,4‐ d ‐mannuronic acid are converted to α ‐1,4‐ l ‐guluronic acid catalysed by C5‐epimerase AlgG encoded by algG gene to produce alternating d ‐mannuronate and l ‐guluronate blocks and stretches of polymannuronate at polymer level (Wolfram et al . ). Therefore, the algG mutants of P. aeruginosa were found to produce homopolymeric alginate containing only polymeric d ‐mannuronic acid residues (Gimmestad et al .…”

Section: Introductionmentioning

confidence: 97%