Download MendeleyStructural insight into substrate specificity of human intestinal maltase-glucoamylase
Ren, L.M., Qin, X.H., Cao, X.F., Wang, L.L., Bai, F., Bai, G., Shen, Y.(2011) Protein Cell 2: 827-836
- PubMed: 22058037
- DOI: https://doi.org/10.1007/s13238-011-1105-3
- Primary Citation of Related Structures:
3TON, 3TOP - PubMed 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.
Organizational Affiliation:
State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin 300071, China.
