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Crystal structure of endo‐xylogalacturonan hydrolase from Aspergillus tubingensis
Author(s) -
Rozeboom Henriëtte J.,
Beldman Gerrit,
Schols Henk A.,
Dijkstra Bauke W.
Publication year - 2013
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.12524
Subject(s) - hydrolase , chemistry , aspergillus , crystal structure , crystal (programming language) , crystallography , stereochemistry , enzyme , biochemistry , computer science , biology , microbiology and biotechnology , programming language
Endo‐xylogalacturonan hydrolase is a member of glycoside hydrolase family 28 ( GH 28) that hydrolyzes the glycosidic bond between two β‐xylose‐substituted galacturonic acid residues in pectin. Presented here is the X ‐ray crystal structure of the endo‐xylogalacturonan hydrolase from A spergillus tubingensis ( X gh A ) at 1.75 Å resolution. The high degree of structural conservation in the active site and catalytic apparatus compared with polygalacturonases indicates that cleavage of the substrate proceeds in essentially the same way as found for the other GH 28 enzymes. Molecular modeling of a xylosylated tri‐galacturonate in the active site identified the amino acid residues involved in substrate binding. They border a substrate‐binding cleft that is much wider than in other polygalacturonases, and can accommodate xylosylated substrates. The most extensive interactions appear to occur at subsite +2, in agreement with the enzyme kinetics results, which showed enhanced activity on substrates with a xylose attached to the galacturonic acid bound at subsite +2. Database Structural data are available in the Protein Data Bank database under accession number 4C2L .