3W38

Sugar beet alpha-glucosidase

Summary for 3W38

• Entry DOI: 10.2210/pdb3w38/pdb
• Related: 3W37 3WEL 3WEM 3WEN 3WEO
• 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, ... (5 entities in total)
• Functional Keywords: alpha-glucosidase, glycoside hydrolase family 31, (beta/alpha)8-barrel, hydrolase, carbohydrate
• Biological source: Beta vulgaris (beet)
• Total number of polymer chains: 1
• Total formula weight: 103496.09

Authors

Tagami, T.,Yamashita, K.,Okuyama, M.,Mori, H.,Yao, M.,Kimura, A. (deposition date: 2012-12-13, release date: 2013-05-29, Last modification date: 2024-10-09)

Primary citation

Tagami, T.,Yamashita, K.,Okuyama, M.,Mori, H.,Yao, M.,Kimura, A.
Molecular basis for the recognition of long-chain substrates by plant & alpha-glucosidase
J.Biol.Chem., 288:19296-19303, 2013

PubMed Abstract: Sugar beet α-glucosidase (SBG), a member of glycoside hydrolase family 31, shows exceptional long-chain specificity, exhibiting higher kcat/Km values for longer malto-oligosaccharides. However, its amino acid sequence is similar to those of other short chain-specific α-glucosidases. To gain structural insights into the long-chain substrate recognition of SBG, a crystal structure complex with the pseudotetrasaccharide acarbose was determined at 1.7 Å resolution. The active site pocket of SBG is formed by a (β/α)8 barrel domain and a long loop (N-loop) bulging from the N-terminal domain similar to other related enzymes. Two residues (Phe-236 and Asn-237) in the N-loop are important for the long-chain specificity. Kinetic analysis of an Asn-237 mutant enzyme and a previous study of a Phe-236 mutant enzyme demonstrated that these residues create subsites +2 and +3. The structure also indicates that Phe-236 and Asn-237 guide the reducing end of long substrates to subdomain b2, which is an additional element inserted into the (β/α)8 barrel domain. Subdomain b2 of SBG includes Ser-497, which was identified as the residue at subsite +4 by site-directed mutagenesis.

PubMed: 23687304
DOI: 10.1074/jbc.M113.465211

Experimental method

X-RAY DIFFRACTION (2.79 Å)