5AWP

Arthrobacter globiformis T6 isomalto-dextranase complexed with isomaltose

Summary for 5AWP

• Entry DOI: 10.2210/pdb5awp/pdb
• Related: 5AWO 5AWQ
• Descriptor: Isomaltodextranase, alpha-D-glucopyranose-(1-6)-beta-D-glucopyranose, PHOSPHATE ION, ... (4 entities in total)
• Functional Keywords: tim barrel, glycoside hydrolase, gh27, carbohydrate binding module, cbm35, hydrolase
• Biological source: Arthrobacter globiformis
• Total number of polymer chains: 1
• Total formula weight: 67672.67

Authors

Tonozuka, T. (deposition date: 2015-07-08, release date: 2015-09-09, Last modification date: 2023-11-08)

Primary citation

Okazawa, Y.,Miyazaki, T.,Yokoi, G.,Ishizaki, Y.,Nishikawa, A.,Tonozuka, T.
Crystal Structure and Mutational Analysis of Isomalto-dextranase, a Member of Glycoside Hydrolase Family 27
J.Biol.Chem., 290:26339-26349, 2015

PubMed Abstract: Arthrobacter globiformis T6 isomalto-dextranase (AgIMD) is an enzyme that liberates isomaltose from the non-reducing end of a polymer of glucose, dextran. AgIMD is classified as a member of the glycoside hydrolase family (GH) 27, which comprises mainly α-galactosidases and α-N-acetylgalactosaminidases, whereas AgIMD does not show α-galactosidase or α-N-acetylgalactosaminidase activities. Here, we determined the crystal structure of AgIMD. AgIMD consists of the following three domains: A, C, and D. Domains A and C are identified as a (β/α)8-barrel catalytic domain and an antiparallel β-structure, respectively, both of which are commonly found in GH27 enzymes. However, domain A of AgIMD has subdomain B, loop-1, and loop-2, all of which are not found in GH27 human α-galactosidase. AgIMD in a complex with trisaccharide panose shows that Asp-207, a residue in loop-1, is involved in subsite +1. Kinetic parameters of the wild-type and mutant enzymes for the small synthetic saccharide p-nitrophenyl α-isomaltoside and the polysaccharide dextran were compared, showing that Asp-207 is important for the catalysis of dextran. Domain D is classified as carbohydrate-binding module (CBM) 35, and an isomaltose molecule is seen in this domain in the AgIMD-isomaltose complex. Domain D is highly homologous to CBM35 domains found in GH31 and GH66 enzymes. The results here indicate that some features found in GH13, -31, and -66 enzymes, such as subdomain B, residues at the subsite +1, and the CBM35 domain, are also observed in the GH27 enzyme AgIMD and thus provide insights into the evolutionary relationships among GH13, -27, -31, -36, and -66 enzymes.

PubMed: 26330557
DOI: 10.1074/jbc.M115.680942

Experimental method

X-RAY DIFFRACTION (2 Å)