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Structural basis for glucose tolerance in GH1 β-glucosidases.
Priscila Oliveira de Giuseppe1, Tatiana de Arruda Campos Brasil Souza1, Flavio Henrique Moreira Souza2
1Brazilian Biosciences National Laboratory, National Center for Research in Energy and Materials, CP 6192, 13083-970 Campinas-SP, Brazil.
Summary
Glucose tolerance in beta-glucosidases (BGs) is key for biomass saccharification. Structural analysis reveals that specific amino acids and active site shape in GH1 BGs enhance glucose tolerance, making them ideal for industrial applications.
Area of Science:
- Biochemistry
- Enzymology
- Structural Biology
Background:
- Product inhibition by glucose limits beta-glucosidases (BGs) in biomass saccharification.
- Some GH1 family BGs show remarkable glucose tolerance or stimulation, unlike typical BGs.
Purpose of the Study:
- To elucidate the structural basis for glucose tolerance and stimulation in GH1 family BGs.
- To compare the structural features of GH1 and GH3 BGs concerning glucose tolerance.
Main Methods:
- X-ray crystallography of a fungal GH1 beta-glucosidase in native and glucose-complexed forms.
- Comparative structural analysis of GH1 and GH3 beta-glucosidases.
Main Results:
- The structure reveals that active site entrance shape and electrostatics, particularly the +2 subsite, dictate glucose tolerance.
- Conserved residues Trp168 and Leu173 in GH1 BGs limit glucose access to the -1 subsite, reducing inhibition.
- GH1 BGs exhibit 10-1000x greater glucose tolerance than GH3 BGs, correlating with their deep, narrow active site cavity.
Conclusions:
- The molecular basis for glucose tolerance in GH1 BGs is linked to active site architecture and specific amino acid residues.
- GH1 BGs are superior to GH3 BGs for biotechnological applications like plant cell-wall saccharification due to enhanced glucose tolerance.
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