Synthesis and application of a highly branched, mechanism-based 2-deoxy-2-fluoro-oligosaccharide inhibitor of endo-xyloglucanases.
Org Biomol Chem
; 16(45): 8732-8741, 2018 11 21.
Article
em En
| MEDLINE
| ID: mdl-30387796
ABSTRACT
Xyloglucan (XyG) is a complex polysaccharide that is ubiquitous and often abundant in the cell walls of terrestrial plants. XyG metabolism is therefore a key component of the global carbon cycle, and hence XyG enzymology is of significant fundamental and applied importance in biomass conversion. To facilitate structure-function analyses of XyG-specific endo-glucanases, we have synthesized a 2',4'-dinitrophenyl 2-deoxy-2-fluoro-ß-glycoside mechanism-based inhibitor based on the highly branched XyG repeating motif XXXG (Xyl3Glc4 ([α-d-Xylp-(1â6)]-ß-d-Glcp-(1â4)-[α-d-Xylp-(1â6)]-ß-d-Glcp-(1â4)-[α-d-Xylp-(1â6)]-ß-d-Glcp-(1â4)-d-Glcp. Key steps in the chemo-enzymatic synthesis included selective enzyme hydrolysis of XyG polysaccharide to produce the core heptasaccharide, per-O-acetylation, α-bromination, reductive glycal formation, electrophilic fluorination, SNAr glycosylation, and Zemplen deprotection. The resulting compound, XXXG(2F)-ß-DNP, specifically labelled the active sites of several endo-(xylo)glucanases by accumulation of a covalent glycosyl-enzyme intermediate, as revealed by intact protein mass spectrometry. Crystallography of a complex with a Cellvibrio japonicus Glycoside Hydrolase Family 5 (GH5) endo-xyloglucanase corroborated the covalent nature of the intermediate, and further revealed the anticipated specificity for the catalytic nucleophile of this anomeric-configuration-retaining glycosidase. This specificity complements that of an analogous XXXG N-bromoacetylglycosylamine inhibitor, which labelled the catalytic acid-base sidechain in the same enzyme [Attia, et al., Biotechnol. Biofuels, 2018, 11, 45]. We anticipate that these inhibitors may find continued use in mechanistic analyses of endo-(xylo)glucanases from diverse GH families.
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01-internacional
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MEDLINE
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En
Ano de publicação:
2018
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Article