3WEO

Sugar beet alpha-glucosidase with acarviosyl-maltohexaose

Summary for 3WEO

• Entry DOI: 10.2210/pdb3weo/pdb
• Related: 3W37 3W38 3WEL 3WEM 3WEN
• Descriptor: Alpha-glucosidase, alpha-L-fucopyranose-(1-3)-[2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)]2-acetamido-2-deoxy-beta-D-glucopyranose, 2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose, ... (8 entities in total)
• Functional Keywords: alpha-glucosidase, glycoside hydrolase family 31, (beta/alpha)8-barrel, acarbose derivative, hydrolase
• Biological source: Beta vulgaris (Sugar beet)
• Total number of polymer chains: 1
• Total formula weight: 105210.69

Authors

Tagami, T.,Yamashita, K.,Okuyama, M.,Mori, H.,Yao, M.,Kimura, A. (deposition date: 2013-07-09, release date: 2014-07-16, Last modification date: 2024-10-16)

Primary citation

Tagami, T.,Yamashita, K.,Okuyama, M.,Mori, H.,Yao, M.,Kimura, A.
Structural advantage of sugar beet alpha-glucosidase to stabilize the Michaelis complex with long-chain substrate
J.Biol.Chem., 290:1796-1803, 2014

PubMed Abstract: The α-glucosidase from sugar beet (SBG) is an exo-type glycosidase. The enzyme has a pocket-shaped active site, but efficiently hydrolyzes longer maltooligosaccharides and soluble starch due to lower Km and higher kcat/Km for such substrates. To obtain structural insights into the mechanism governing its unique substrate specificity, a series of acarviosyl-maltooligosaccharides was employed for steady-state kinetic and structural analyses. The acarviosyl-maltooligosaccharides have a longer maltooligosaccharide moiety compared with the maltose moiety of acarbose, which is known to be the transition state analog of α-glycosidases. The clear correlation obtained between log Ki of the acarviosyl-maltooligosaccharides and log(Km/kcat) for hydrolysis of maltooligosaccharides suggests that the acarviosyl-maltooligosaccharides are transition state mimics. The crystal structure of the enzyme bound with acarviosyl-maltohexaose reveals that substrate binding at a distance from the active site is maintained largely by van der Waals interactions, with the four glucose residues at the reducing terminus of acarviosyl-maltohexaose retaining a left-handed single-helical conformation, as also observed in cycloamyloses and single helical V-amyloses. The kinetic behavior and structural features suggest that the subsite structure suitable for the stable conformation of amylose lowers the Km for long-chain substrates, which in turn is responsible for higher specificity of the longer substrates.

PubMed: 25451917
DOI: 10.1074/jbc.M114.606939

Experimental method

X-RAY DIFFRACTION (1.45 Å)