title: Dextranase from Penicillium minioluteum: reaction course, crystal structure, and product complex.
abstract: Dextranase catalyzes the hydrolysis of the alpha-1,6-glycosidic linkage in dextran polymers. The structure of dextranase, Dex49A, from Penicillium minioluteum was solved in the apo-enzyme and product-bound forms. The main domain of the enzyme is a right-handed parallel beta helix, which is connected to a beta sandwich domain at the N terminus. In the structure of the product complex, isomaltose was found to bind in a crevice on the surface of the enzyme. The glycosidic oxygen of the glucose unit in subsite +1 forms a hydrogen bond to the suggested catalytic acid, Asp395. By NMR spectroscopy the reaction course was shown to occur with net inversion at the anomeric carbon, implying a single displacement mechanism. Both Asp376 and Asp396 are suitably positioned to activate the water molecule that performs the nucleophilic attack. A new clan that links glycoside hydrolase families 28 and 49 is suggested.
authors.affiliation: Department of Cell and Molecular Biology, Biomedical Centre, University of Uppsala, Box 596, SE-751 24 Uppsala, Sweden.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Larsson
authors.forename: Rolf
authors.initials: R
authors.lastname: Andersson
authors.forename: Jerry
authors.initials: J
authors.lastname: Ståhlberg
authors.forename: Lennart
authors.initials: L
authors.lastname: Kenne
authors.forename: T Alwyn
authors.initials: TA
authors.lastname: Jones
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D003910:Dextranase / Q000737:chemistry* / Q000378:metabolism; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010407:Penicillium / Q000201:enzymology*; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary
chemical_list: D003910:Dextranase