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A gene encoding an exo-beta-glucosidase from Cellvibrio mixtus
H Sakellaris1, J M Manners, J M Pemberton
1Department of Microbiology, University of Queensland, Brisbane, 4072, Australia.
Current Microbiology
|October 1, 1997
Summary
Cellvibrio mixtus beta-glucan degradation involves the Lam2 exohydrolase, an enzyme that breaks down soluble beta-glucans. This research identifies and characterizes the lam2 gene, crucial for further polysaccharide breakdown.
Area of Science:
- Microbiology
- Enzymology
- Biochemistry
Background:
- Cellvibrio mixtus degrades soil beta-glycan polysaccharides using endohydrolytic enzymes.
- Further degradation of soluble oligosaccharides for cellular uptake in C. mixtus remains poorly understood.
Purpose of the Study:
- To clone and characterize the lam2 gene encoding an exohydrolase involved in beta-glucan degradation in C. mixtus.
- To elucidate the role of the Lam2 enzyme in the later stages of beta-glucan breakdown.
Main Methods:
- Gene cloning of lam2 from C. mixtus.
- In vivo transcription/translation and deletion analyses to determine protein size.
- Enzyme substrate specificity and product analysis (laminarin hydrolysis).
- Southern analysis to determine gene copy number.
Main Results:
- The lam2 gene was cloned, encoding a ~91 kDa protein.
- Lam2 exhibits broad substrate specificity for various beta-glucans (beta-1,3-, beta-1,4-, beta-1,6-, beta-1,3-1,4-linked).
- Lam2 functions as an exohydrolase, releasing terminal glucose residues, classifying it as a beta-glucosidase (EC3.2.1.21).
- A single copy of the lam2 gene is present on the C. mixtus chromosome.
Conclusions:
- The Lam2 enzyme plays a significant role in the catabolism of soluble beta-glucans in Cellvibrio mixtus.
- Lam2's exohydrolase activity and substrate specificity contribute to the complete degradation of beta-glucans.