Structure of a carbohydrate esterase from Bacillus anthracis

<p>Family 4 carbohydrate esterases (CEs)catalyse the N- or O-deacetylation of substrates such asacetylated xylan, chitin, and peptidoglycan. CEs are classified into 14 families by sequence homology (see http://afmb.cnrs-mrs.fr/CAZY1). Family 4 is by far the largest of the CE families, with over 1000 open reading frames. The structure of CE4 enzymes from a number of bacterial species have been solved, including the peptidoglycan deacetylases from Streptococcus pneumoniae and Bacillus subtilis,3 acetyl xylan esterases from Clostridium thermocellum and Streptomyces lividans,4 and an enzyme of unknown specificity from Pseudomonas aeruginosa (PDBcode 1Z7A). CE4 enzymes contain a conserved NodBhomology domain, and adopt a distorted (a/b)8 barrel fold.Most of the structures contain a divalent ion in the activesite that is necessary for enzyme activity2,4 and which iscoordinated by highly conserved histidine and aspartateresidues.</p>