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beta-Xylosidase from Aspergillus niger 15: purification and properties
Journal of Applied Biochemistry
|August 1, 1983
Summary
This study isolated a homogeneous beta-xylosidase enzyme from Aspergillus niger, demonstrating broad substrate specificity and transglycosylase activity. The purified enzyme exhibits optimal activity at 70°C and pH 3.8-4.0, with notable stability.
Area of Science:
- Enzymology
- Microbiology
- Biochemistry
Background:
- Hemicellulase preparations from microorganisms are sources of valuable enzymes.
- Aspergillus niger is a well-known fungus with diverse enzymatic capabilities.
- Characterizing specific enzymes like beta-xylosidase is crucial for understanding their industrial and biological roles.
Purpose of the Study:
- To isolate and characterize a homogeneous beta-xylosidase from Aspergillus niger.
- To determine the enzyme's substrate specificity, kinetic properties, and stability.
- To investigate potential applications based on its enzymatic activities.
Main Methods:
- Enzyme isolation using ethanol fractionation and multiple chromatography techniques (Sephadex G-50, DE-52, SP C-50, G-200).
- Enzyme characterization through gel filtration, ultracentrifugation, SDS-PAGE, isoelectric focusing, and amino acid analysis.
- Enzyme activity assays using p-nitrophenyl-beta-D-xylopyranoside (p-NPX) and kinetic analysis with D-xylose.
Main Results:
- A homogeneous beta-xylosidase was purified with a 199-fold increase in specific activity (35.2 units/mg protein).
- The enzyme exhibited broad activity including beta-D-glucosidase, beta-D-galactosidase, and alpha-L-arabinosidase.
- Determined molecular weight (253,000 Da by gel filtration, 122,000 Da by SDS-PAGE), isoelectric point (pI 4.9), and optimal conditions (70°C, pH 3.8-4.0).
- The enzyme showed stability over a broad pH range (3-8) and moderate thermal stability (up to 50°C for 1 hour).
- D-Xylose acted as a competitive inhibitor (Ki = 2.9 mM), and transglycosylase activity was observed.
Conclusions:
- The purified Aspergillus niger beta-xylosidase is a robust enzyme with significant specific activity and broad substrate range.
- Its physicochemical properties and stability suggest potential utility in industrial applications, such as biomass processing.
- Further research into its transglycosylase activity could reveal novel biochemical pathways or applications.