1bgg
|
GLUCOSIDASE A FROM BACILLUS POLYMYXA COMPLEXED WITH GLUCONATE
OverviewOverview
Family 1 glycosyl hydrolases are a very relevant group of enzymes because, of the diversity of biological roles in which they are involved, and their, generalized occurrence in all sorts of living organisms. The biological, plasticity of these enzymes is a consequence of the variety of, beta-glycosidic substrates that they can hydrolyze: disaccharides such as, cellobiose and lactose, phosphorylated disaccharides, cyanogenic, glycosides, etc. The crystal structure of BglA, a member of the family, has been determined in the native state and complexed with gluconate, ligand, at 2.4 A and 2.3 A resolution, respectively. The subunits of the, octameric enzyme display the (alpha/beta)8 barrel structural fold, previously reported for other family 1 enzymes. However, significant, structural differences have been encountered in the loops surrounding the, active-center cavity. These differences make a wide and extended cavity in, BglA, which seems to be able to accommodate substrates longer than, cellobiose, its natural substrate. Furthermore, a third sub-site is, encountered, which might have some connection with the transglycosylating, activity associated to this enzyme and its certain activity against, beta-1,4 oligosaccharides composed of more than two units of glucose. The, particular geometry of the cavity which contains the active center of BglA, must therefore account for both, hydrolytic and transglycosylating, activities. A potent and well known inhibitor of different glycosidases, D-glucono-1,5-lactone, was used in an attempt to define interactions of, the substrate with specific protein residues. Although the lactone has, transformed into gluconate under crystallizing conditions, the open, species still binds the enzyme, the conformation of its chain mimicking, the true inhibitor. From the analysis of the enzyme-ligand hydrogen, bonding interactions, a detailed picture of the active center can be, drawn, for a family 1 enzyme. In this way, Gln20, His121, Tyr296, Glu405, and Trp406 are identified as determinant residues in the recognition of, the substrate. In particular, two bidentate hydrogen bonds made by Gln20, and Glu405, could conform the structural explanation for the ability of, most members of the family for displaying both, glucosidase and, galactosidase activity.
About this StructureAbout this Structure
1BGG is a Single protein structure of sequence from Paenibacillus polymyxa with GCO as ligand. Active as Beta-glucosidase, with EC number 3.2.1.21 Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure of beta-glucosidase A from Bacillus polymyxa: insights into the catalytic activity in family 1 glycosyl hydrolases., Sanz-Aparicio J, Hermoso JA, Martinez-Ripoll M, Lequerica JL, Polaina J, J Mol Biol. 1998 Jan 23;275(3):491-502. PMID:9466926
Page seeded by OCA on Tue Nov 20 11:38:09 2007