Affordable Access

Publisher Website

Crystal structure of α-1,4-glucan lyase, a unique glycoside hydrolase family member with a novel catalytic mechanism.

Authors
Type
Published Article
Journal
Journal of Biological Chemistry
0021-9258
Publisher
American Society for Biochemistry and Molecular Biology
Publication Date
Volume
288
Issue
37
Pages
26764–26774
Identifiers
DOI: 10.1074/jbc.M113.485896
PMID: 23902768
Source
Medline
Keywords
  • 1-Deoxynojirimycin
  • Acarbose
  • Anhydrofructose Pathway
  • Carbohydrate Binding Site
  • Crystal Structure
  • Enzyme Mechanisms
  • Glycoside Hydrolases
  • Glycosylation Inhibitors
  • Glycosylenzyme Intermediate
  • X-Ray Crystallography

Abstract

α-1,4-Glucan lyase (EC 4.2.2.13) from the red seaweed Gracilariopsis lemaneiformis cleaves α-1,4-glucosidic linkages in glycogen, starch, and malto-oligosaccharides, yielding the keto-monosaccharide 1,5-anhydro-D-fructose. The enzyme belongs to glycoside hydrolase family 31 (GH31) but degrades starch via an elimination reaction instead of hydrolysis. The crystal structure shows that the enzyme, like GH31 hydrolases, contains a (β/α)8-barrel catalytic domain with B and B' subdomains, an N-terminal domain N, and the C-terminal domains C and D. The N-terminal domain N of the lyase was found to bind a trisaccharide. Complexes of the enzyme with acarbose and 1-dexoynojirimycin and two different covalent glycosyl-enzyme intermediates obtained with fluorinated sugar analogues show that, like GH31 hydrolases, the aspartic acid residues Asp(553) and Asp(665) are the catalytic nucleophile and acid, respectively. However, as a unique feature, the catalytic nucleophile is in a position to act also as a base that abstracts a proton from the C2 carbon atom of the covalently bound subsite -1 glucosyl residue, thus explaining the unique lyase activity of the enzyme. One Glu to Val mutation in the active site of the homologous α-glucosidase from Sulfolobus solfataricus resulted in a shift from hydrolytic to lyase activity, demonstrating that a subtle amino acid difference can promote lyase activity in a GH31 hydrolase.

There are no comments yet on this publication. Be the first to share your thoughts.

Statistics

Seen <100 times
0 Comments
F