Investigation of the functional relevance of the catalytically important Glu(28) in family 51 arabinosidases |
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Authors: | Ferchichi Mounir Rémond Caroline Simo Roselyne O'Donohue Michael J |
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Institution: | Institut National de la Recherche Agronomique, UMR FARE, 8, rue Gabriel Voisin, P.O. Box 316, 51688 Cedex 2 Reims, France. |
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Abstract: | The alpha-L-arabinofuranosidase (AbfD3) from Thermobacillus xylanilyticus is a family 51 glycosyl hydrolase. According to classification hierarchy, family 51 belongs to clan GH-A. While the major GH-A motifs, the catalytic acid-base and nucleophile, are conserved in AbfD3, a third catalytically important residue (Glu(28)) does not appear to be analogous to any known GH-A motif. To evaluate the importance of Glu(28), bioinformatics analyses and site-saturation mutagenesis were performed. The results indicate that Glu(28) forms part of a family 51 arabinosidase motif which might be functionally homologous to a conserved N-terminal motif found in exo-acting enzymes from families 1 and 5. Importantly, the data reveal that Glu(28) is a key determinant of substrate recognition in the -1 subsite, where it may also play an important role in water-mediated deglycosylation of the glycosyl-enzyme covalent intermediate. |
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Keywords: | L-Arabinofuranosidase" target="_blank">α-L-Arabinofuranosidase Glycosyl hydrolase Family 51 Clan GH-A Transglycosylation |
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