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Structural basis for broad substrate specificity in higher plant beta-D-glucan glucohydrolases
Maria Hrmova1, Ross De Gori, Brian J Smith
1Department of Plant Science, University of Adelaide, Waite Campus, Glen Osmond, South Australia 5064, Australia.
The Plant Cell
|May 30, 2002
Summary
Family 3 beta-D-glucan glucohydrolases in plants exhibit broad substrate specificity. Structural analysis reveals how their active site accommodates diverse beta-D-glucans, enabling varied developmental functions.
Area of Science:
- Plant Biochemistry
- Enzymology
- Structural Biology
Background:
- Family 3 beta-D-glucan glucohydrolases are crucial enzymes found widely in higher plants.
- These enzymes are responsible for hydrolyzing beta-D-glucans and beta-D-oligoglucosides.
Purpose of the Study:
- To elucidate the structural basis for the broad substrate specificity of plant Family 3 beta-D-glucan glucohydrolases.
- To understand how enzyme-substrate interactions facilitate diverse functions in plant development.
Main Methods:
- X-ray crystallography of barley beta-D-glucan glucohydrolase with substrate analogs.
- Molecular modeling of enzyme/substrate complexes.
Main Results:
- Detailed atomic interactions reveal a tightly bound glucosyl residue at subsite -1 via extensive hydrogen bonding.
- A more flexible binding at subsite +1, influenced by Trp residues, allows accommodation of varied substrate conformations.
- The active site architecture supports diverse spatial arrangements of adjacent beta-D-glucosyl residues.
Conclusions:
- The structural flexibility of the active site, particularly at subsite +1, explains the broad substrate specificity.
- This broad specificity enables Family 3 beta-D-glucan glucohydrolases to perform essential roles throughout plant development.