6LGA

Bombyx mori GH13 sucrose hydrolase

Summary for 6LGA

• Entry DOI: 10.2210/pdb6lga/pdb
• Descriptor: Sucrose hydrolase, MAGNESIUM ION, CALCIUM ION, ... (6 entities in total)
• Functional Keywords: sucrose, glycoside hydrolase, gh13, hydrolase
• Biological source: Bombyx mori (Silk moth)
• Total number of polymer chains: 2
• Total formula weight: 138242.12

Authors

Miyazaki, T. (deposition date: 2019-12-05, release date: 2020-05-20, Last modification date: 2023-11-22)

Primary citation

Miyazaki, T.,Park, E.Y.
Structure-function analysis of silkworm sucrose hydrolase uncovers the mechanism of substrate specificity in GH13 subfamily 17exo-alpha-glucosidases.
J.Biol.Chem., 295:8784-8797, 2020

PubMed Abstract: The domestic silkworm expresses two sucrose-hydrolyzing enzymes, BmSUH and BmSUC1, belonging to glycoside hydrolase family 13 subfamily 17 (GH13_17) and GH32, respectively. BmSUH has little activity on maltooligosaccharides, whereas other insect GH13_17 α-glucosidases are active on sucrose and maltooligosaccharides. Little is currently known about the structural mechanisms and substrate specificity of GH13_17 enzymes. In this study, we examined the crystal structures of BmSUH without ligands; in complexes with substrates, products, and inhibitors; and complexed with its covalent intermediate at 1.60-1.85 Å resolutions. These structures revealed that the conformations of amino acid residues around subsite -1 are notably different at each step of the hydrolytic reaction. Such changes have not been previously reported among GH13 enzymes, including - and -acting hydrolases, such as α-glucosidases and α-amylases. Amino acid residues at subsite +1 are not conserved in BmSUH and other GH13_17 α-glucosidases, but subsite -1 residues are absolutely conserved. Substitutions in three subsite +1 residues, Gln, Tyr, and Glu, decreased sucrose hydrolysis and increased maltase activity of BmSUH, indicating that these residues are key for determining its substrate specificity. These results provide detailed insights into structure-function relationships in GH13 enzymes and into the molecular evolution of insect GH13_17 α-glucosidases.

PubMed: 32381508
DOI: 10.1074/jbc.RA120.013595

Experimental method

X-RAY DIFFRACTION (1.85 Å)