4a3h: Difference between revisions

The enzymatic hydrolysis of O-glycosidic linkages is one of the most, diverse and widespread reactions in nature and involves a classic, "textbook" enzyme mechanism. A multidisciplinary analysis of a, beta-glycoside hydrolase, the Cel5A from Bacillus agaradhaerens, is, presented in which the structures of each of the native, substrate, covalent-intermediate, and product complexes have been determined and, their interconversions analyzed kinetically, providing unprecedented, insights into the mechanism of this enzyme class. Substrate is bound in a, distorted 1S3 skew-boat conformation, thereby presenting the anomeric, carbon appropriately for nucleophilic attack as well as satisfying the, stereoelectronic requirements for an incipient oxocarbenium ion. Leaving, group departure results in the trapping of a covalent, alpha-glycosyl-enzyme intermediate in which the sugar adopts an, undistorted 4C1 conformation. Finally, hydrolysis of this intermediate, yields a product complex in which the sugar is bound in a partially, disordered mode, consistent with unfavorable interactions and low product, affinity.

4A3H is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bacillus_agaradhaerens Bacillus agaradhaerens] with DCB as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Cellulase Cellulase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.4 3.2.1.4] Structure known Active Sites: ACI and NUC. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=4A3H OCA].  

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