Structural insight into substrate specificity of human intestinal maltase-glucoamylase
Protein & Cell
;
(12): 827-836, 2011.
Article
in English
| WPRIM
| ID: wpr-757034
ABSTRACT
Human maltase-glucoamylase (MGAM) hydrolyzes linear alpha-1,4-linked oligosaccharide substrates, playing a crucial role in the production of glucose in the human lumen and acting as an efficient drug target for type 2 diabetes and obesity. The amino- and carboxyl-terminal portions of MGAM (MGAM-N and MGAM-C) carry out the same catalytic reaction but have different substrate specificities. In this study, we report crystal structures of MGAM-C alone at a resolution of 3.1 Å, and in complex with its inhibitor acarbose at a resolution of 2.9 Å. Structural studies, combined with biochemical analysis, revealed that a segment of 21 amino acids in the active site of MGAM-C forms additional sugar subsites (+ 2 and + 3 subsites), accounting for the preference for longer substrates of MAGM-C compared with that of MGAM-N. Moreover, we discovered that a single mutation of Trp1251 to tyrosine in MGAM-C imparts a novel catalytic ability to digest branched alpha-1,6-linked oligosaccharides. These results provide important information for understanding the substrate specificity of alpha-glucosidases during the process of terminal starch digestion, and for designing more efficient drugs to control type 2 diabetes or obesity.
Full text:
Available
Index:
WPRIM (Western Pacific)
Main subject:
Oligosaccharides
/
Pichia
/
Protein Binding
/
Substrate Specificity
/
Surface Properties
/
Recombinant Proteins
/
Molecular Sequence Data
/
Kinetics
/
Chemistry
/
Mutagenesis, Site-Directed
Limits:
Humans
Language:
English
Journal:
Protein & Cell
Year:
2011
Type:
Article
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