ArticleApplied and environmental microbiology2022
Mechanistic Basis for Understanding the Dual Activities of the Bifunctional Azotobacter vinelandii Mannuronan C-5-Epimerase and Alginate Lyase AlgE7.
Article in Applied and environmental microbiology, 2022. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 3 papers.
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3 citing papers in PubMed, 16 citations in OpenAlex.
- Mode of Action of AlgE1: A Modular Mannuronate C-5 Epimerase.Biochemistry · 2025Article
- Diatom heterotrophy on brown algal polysaccharides emerged through horizontal gene transfer, gene duplication, and neofunctionalization.PLoS biology · 2025Article
- Computational modeling of the molecular basis for the calcium-dependence of the mannuronan C-5 epimerase AvAlgE6 fromComputational and structural biotechnology journal · 2023Article
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8 authors at 4 institutions in 2 countries.
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Abstract
The structure and functional properties of alginates are dictated by the monomer composition and molecular weight distribution. Mannuronan C-5-epimerases determine the monomer composition by catalyzing the epimerization of β-d-mannuronic acid (M) residues into α-l-guluronic acid (G) residues. The molecular weight is affected by alginate lyases, which catalyze a β-elimination mechanism that cleaves alginate chains. The reaction mechanisms for the epimerization and lyase reactions are similar, and some enzymes can perform both reactions. These dualistic enzymes share high sequence identity with mannuronan C-5-epimerases without lyase activity. The mechanism behind their activity and the amino acid residues responsible for it are still unknown. We investigate mechanistic determinants involved in the bifunctional epimerase and lyase activity of AlgE7 from Azotobacter vinelandii. Based on sequence analyses, a range of AlgE7 variants were constructed and subjected to activity assays and product characterization by nuclear magnetic resonance (NMR) spectroscopy. Our results show that calcium promotes lyase activity, whereas NaCl reduces the lyase activity of AlgE7. By using defined polymannuronan (polyM) and polyalternating alginate (polyMG) substrates, the preferred cleavage sites of AlgE7 were found to be M|XM and G|XM, where X can be either M or G. From the study of AlgE7 mutants, R148 was identified as an important residue for the lyase activity, and the point mutant R148G resulted in an enzyme with only epimerase activity. Based on the results obtained in the present study, we suggest a unified catalytic reaction mechanism for both epimerase and lyase activities where H154 functions as the catalytic base and Y149 functions as the catalytic acid.
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