1ods: Difference between revisions

Esterases and deacetylases active on carbohydrate ligands have been, classified into 14 families based upon amino acid sequence similarities., Enzymes from carbohydrate esterase family seven (CE-7) are unusual in that, they display activity towards both acetylated xylooligosaccharides and the, antibiotic, cephalosporin C. The 1.9A structure of the multifunctional, CE-7 esterase (hereinafter CAH) from Bacillus subtilis 168 reveals a, classical alpha/beta hydrolase fold encased within a 32 hexamer. This is, the first example of a hexameric alpha/beta hydrolase and is further, evidence of the versatility of this particular fold, which is used in a, wide variety of biological contexts. A narrow entrance tunnel leads to the, centre of the molecule, where the six active-centre catalytic triads point, towards the tunnel interior and thus are sequestered away from cytoplasmic, contents. By analogy to self-compartmentalising proteases, the tunnel, entrance may function to hinder access of large substrates to the, poly-specific active centre. This would explain the observation that the, enzyme is active on a variety of small, acetylated molecules. The, structure of an active site mutant in complex with the reaction product, acetate, reveals details of the putative oxyanion binding site, and, suggests that substrates bind predominantly through non-specific contacts, with protein hydrophobic residues. Protein residues involved in catalysis, are tethered by interactions with protein excursions from the canonical, alpha/beta hydrolase fold. These excursions also mediate quaternary, structure maintenance, so it would appear that catalytic competence is, only achieved on protein multimerisation. We suggest that the acetyl xylan, esterase (EC 3.1.1.72) and cephalosporin C deacetylase (EC 3.1.1.41), enzymes of the CE-7 family represent a single class of proteins with a, multifunctional deacetylase activity against a range of small substrates.

1ODS is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bacillus_subtilis Bacillus subtilis] with CL and MG as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Cephalosporin-C_deacetylase Cephalosporin-C deacetylase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.1.1.41 3.1.1.41] Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1ODS OCA].  

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