Article: Regioselective degradation of [beta] 1,3 glucan by ferrous ion and hydrogen peroxide (Fenton oxidation)
Carbohydrate research. 2020 Nov., v. 497
2020
Abstract: Many species use Fe⁺² and H₂O₂ to oxidize a wide variety of compounds to simpler molecules. Both pathogen killing by leukocytes (neutrophils and lymphocytes) and degradation of cellulose by brown rot fungi rely on excretion of Fe⁺² ions and H₂O₂, the ... ...
| Abstract | Many species use Fe⁺² and H₂O₂ to oxidize a wide variety of compounds to simpler molecules. Both pathogen killing by leukocytes (neutrophils and lymphocytes) and degradation of cellulose by brown rot fungi rely on excretion of Fe⁺² ions and H₂O₂, the Fenton reagent. To elucidate the mechanism of Fenton oxidation of carbohydrates, β1,3 glucan (laminaran), a major fungal wall polysaccharide, was oxidized using a molar ratio of monomer/Fe⁺²/H₂O₂ of 10:1:1 (primarily). We labeled the reaction products and profiled them as fluorescent-labeled molecules in polyacrylamide gels and as hydrophobic-tagged molecules using reverse phase liquid chromatography/mass spectrometry (HPLC/MS).Sub-stoichiometric concentrations of Fe⁺² and H₂O₂ fragmented laminaran into smaller molecules containing carbonyl and carboxylic acid groups visible on fluorescent-labeled carbohydrate polyacrylamide gel electrophoresis. HPLC/MS analysis of glucan fragments showed masses consistent with six classes of molecules: aldoses, dialdoses, uronic acids, hexosuloses, aldonic acids, and hexulosonic acids.The results were consistent with published mechanisms where hydrogen radical (H•) abstraction from a C–H or O–H bond begins a cascade of reactions leading to 1) C–C bond cleavage to produce aldose/dialdose pairs; 2) oxo-group (O =) addition to produce uronic and aldonic acids; 3) hydroxyl group (HO-) addition to produce gluconolactone and hexosuloses; and 4) hexulosonic acids. Most products resulted from regioselective H• abstractions characteristic of oxidations by ferryl-oxo ion [(FeO)⁺²] or perferryl-oxo ion [(FeO)⁺³] in close contact with specific positions in the glycan. Therefore, oxidations initiated by regioselectively-bound Fe ions were the predominant initiators of polysaccharide degradations. |
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| Keywords | aldoses ; carboxylic acids ; cellulose ; cleavage (chemistry) ; excretion ; fluorescent labeling ; gluconolactone ; hydrogen ; hydrogen peroxide ; mass spectrometry ; neutrophils ; oxidation ; pathogens ; polyacrylamide ; polyacrylamide gel electrophoresis ; regioselectivity ; research ; reversed-phase liquid chromatography |
| Language | English |
| Dates of publication | 2020-11 |
| Publishing place | Elsevier Ltd |
| Document type | Article |
| Note | NAL-AP-2-clean |
| ZDB-ID | 1435-7 |
| ISSN | 1873-426X ; 0008-6215 |
| ISSN (online) | 1873-426X |
| ISSN | 0008-6215 |
| DOI | 10.1016/j.carres.2020.108124 |
| Database | NAL-Catalogue (AGRICOLA) |
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