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Structural insights into substrate specificity and function of glucodextranase
Masahiro Mizuno1, Takashi Tonozuka, Saori Suzuki
1Department of Applied Biological Science, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan.
The Journal of Biological Chemistry
|December 9, 2003
Summary
A novel glucodextranase (iGDase) from Arthrobacter globiformis hydrolyzes dextran linkages. Structural analysis reveals unique domains (B and C) and differences in substrate binding compared to glucoamylases.
Area of Science:
- Enzymology
- Structural Biology
- Biochemistry
Background:
- Glucodextranase (iGDase) from Arthrobacter globiformis I42 hydrolyzes alpha-1,6-glucosidic linkages in dextran.
- It produces beta-D-glucose through an inverting mechanism and belongs to glycoside hydrolase family 15 (GH15).
Purpose of the Study:
- To clone the iGDase gene.
- To determine the crystal structures of iGDase in its unliganded form and complexed with acarbose.
Main Methods:
- Gene cloning of iGDase.
- X-ray crystallography to determine structures at 2.42-A resolution.
- Structural comparison with bacterial glucoamylases (GAs).
Main Results:
- The iGDase structure comprises four domains: N, A, B, and C.
- Domains A and N are similar to bacterial GAs and involved in catalysis.
- Domains B and C are unique to iGDase; domain C shows homology to pullulanase and glycohydrolase domains.
Conclusions:
- iGDase possesses unique structural features (domains B and C) not found in bacterial GAs.
- Substrate binding pocket differences at subsite 3 suggest distinct substrate recognition mechanisms compared to GAs.