Endo-beta-Glucanase from Acetobacter xylinum: Purification andCharacterization

Area of Science:

• Biochemistry
• Enzymology
• Microbiology

Background:

• Acetobacter xylinum KU-1 is known for cellulose production.
• Extracellular enzymes secreted by bacteria play crucial roles in various biological processes.
• Endo-beta-glucanases are enzymes that degrade beta-glucans, important components in plant cell walls and microbial structures.

Purpose of the Study:

• To purify and characterize the extracellular endo-beta-glucanase produced by Acetobacter xylinum KU-1.
• To investigate the enzyme's properties, including optimal activity, stability, and substrate specificity.
• To determine the enzyme's molecular weight and kinetic parameters.

Main Methods:

• Purification using ion-exchange chromatography (DEAE- and CM- Toyopearl 650M), hydrophobic chromatography (Butyl-Toyopearl 650M), and gel filtration (Toyopearl HW-50).
• Enzyme activity assays at various pH and temperature conditions.
• Determination of molecular weight using SDS-PAGE and gel filtration.
• Kinetic analysis including Km and Vmax determination for carboxymethylcellulose hydrolysis.
• Substrate specificity analysis using cello-oligosaccharides.

Main Results:

• The enzyme was purified to homogeneity.
• Optimal activity was observed at pH 5 and 50°C, with stability up to 50°C.
• The enzyme is monomeric with an estimated molecular weight of approximately 39,000-41,000 Da.
• It exhibits competitive inhibition by Hg2+ (Ki = 7 μM) and activation by Co2+.
• Hydrolyzed carboxymethylcellulose (Km = 30 mg/ml, Vmax = 1.2 μM/min) and cellohexaose/cellopentaose, but not smaller cello-oligosaccharides.

Conclusions:

• Acetobacter xylinum KU-1 secretes a monomeric endo-beta-glucanase with specific biochemical properties.
• The enzyme demonstrates significant activity against carboxymethylcellulose and larger cello-oligosaccharides.
• These findings highlight the potential of this enzyme in biotechnological applications involving cellulose degradation.