Structural insight into substrate specificity of human intestinal maltase-glucoamylase.
10.1007/s13238-011-1105-3
- Author:
Limei REN
1
;
Xiaohong QIN
;
Xiaofang CAO
;
Lele WANG
;
Fang BAI
;
Gang BAI
;
Yuequan SHEN
Author Information
1. State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin 300071, China.
- Publication Type:Journal Article
- MeSH:
Acarbose;
chemistry;
Amino Acid Sequence;
Catalytic Domain;
Crystallography, X-Ray;
Glycoside Hydrolase Inhibitors;
Humans;
Hydrogen Bonding;
Intestines;
enzymology;
Kinetics;
Maltose;
chemistry;
Molecular Sequence Data;
Mutagenesis, Site-Directed;
Mutation, Missense;
Oligosaccharides;
chemistry;
Pichia;
Protein Binding;
Recombinant Proteins;
antagonists & inhibitors;
chemistry;
genetics;
Substrate Specificity;
Surface Properties;
alpha-Glucosidases;
chemistry;
genetics
- From:
Protein & Cell
2011;2(10):827-836
- CountryChina
- Language:English
-
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.
