3TOP

Crystral Structure of the C-terminal Subunit of Human Maltase-Glucoamylase in Complex with Acarbose

Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.88 Å
  • R-Value Free: 0.284 
  • R-Value Work: 0.218 
  • R-Value Observed: 0.222 

wwPDB Validation   3D Report Full Report


This is version 2.0 of the entry. See complete history. 


Literature

Structural 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

  • DOI: 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 ...

    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.



Macromolecules
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(by identity cutoff)  |  Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
Maltase-glucoamylase, intestinal A, B908Homo sapiensMutation(s): 0 
Gene Names: MGAM, MGA, MGAML
EC: 3.2.1.20 (PDB Primary Data), 3.2.1.3 (PDB Primary Data)
Find proteins for O43451 (Homo sapiens)
Explore O43451 
Go to UniProtKB:  O43451
NIH Common Fund Data Resources
PHAROS:  O43451
GTEx:  ENSG00000257335
Protein Feature View
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  • Reference Sequence
Oligosaccharides

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Entity ID: 2
MoleculeChainsChain Length2D Diagram Glycosylation3D Interactions
4,6-dideoxy-4-{[(1S,4R,5S,6S)-4,5,6-trihydroxy-3-(hydroxymethyl)cyclohex-2-en-1-yl]amino}-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose
C, D
3 N/A N/A Oligosaccharides Interaction
Small Molecules
External Ligand Annotations 
IDBinding Affinity (Sequence Identity %)
ACRIC50:  15200   nM  BindingDB
Biologically Interesting Molecules (External Reference) 1 Unique
Entity ID: 2
IDChainsNameType/Class2D Diagram3D Interactions
PRD_900007
Query on PRD_900007		C, Dalpha-acarboseOligosaccharide /  Inhibitor

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Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.88 Å
  • R-Value Free: 0.284 
  • R-Value Work: 0.218 
  • R-Value Observed: 0.222 
  • Space Group: P 43 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 105.501α = 90
b = 105.501β = 90
c = 516.561γ = 90
Software Package:
Software NamePurpose
HKL-2000data collection
PHASESphasing
PHENIXrefinement
HKL-2000data reduction
HKL-2000data scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2011-11-23
    Type: Initial release
  • Version 2.0: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Atomic model, Data collection, Database references, Derived calculations, Non-polymer description, Structure summary