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Structural Basis of Chitin Oligosaccharide Deacetylation
Author(s) -
Andrés Eduardo,
AlbesaJové David,
Biarnés Xevi,
Moerschbacher Bruno M.,
Guerin Marcelo E.,
Planas Antoni
Publication year - 2014
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201400220
Subject(s) - chitin , chemistry , acetylation , chitobiose , oligosaccharide , stereochemistry , enzyme , active site , biochemistry , chitosan , gene
Cell signaling and other biological activities of chitooligosaccharides (COSs) seem to be dependent not only on the degree of polymerization, but markedly on the specific de‐N‐acetylation pattern. Chitin de‐N‐acetylases (CDAs) catalyze the hydrolysis of the acetamido group in GlcNAc residues of chitin, chitosan, and COS. A major challenge is to understand how CDAs specifically define the distribution of GlcNAc and GlcNH 2 moieties in the oligomeric chain. We report the crystal structure of the Vibrio cholerae CDA in four relevant states of its catalytic cycle. The two enzyme complexes with chitobiose and chitotriose represent the first 3D structures of a CDA with its natural substrates in a productive mode for catalysis, thereby unraveling an induced‐fit mechanism with a significant conformational change of a loop closing the active site. We propose that the deacetylation pattern exhibited by different CDAs is governed by critical loops that shape and differentially block accessible subsites in the binding cleft of CE4 enzymes.