beta-Mannosidase from the mushroom Polyporus sulfureus

Area of Science:

• Biochemistry
• Enzymology
• Glycobiology

Background:

• Beta-D-mannosidase (EC 3.2.1.25) is crucial for analyzing complex carbohydrate structures.
• Enzymes with high specificity are valuable tools in biochemical research.
• Polyporus sulfureus is a novel source for enzyme isolation.

Purpose of the Study:

• To isolate and purify beta-D-mannosidase from Polyporus sulfureus.
• To characterize the enzyme's properties and substrate specificity.
• To evaluate its potential for structural studies of heterosaccharides.

Main Methods:

• Enzyme purification using ammonium sulfate fractionation, Sephadex G-100 filtration, DEAE-cellulose, and hydroxylapatite chromatography.
• Analysis of enzyme purity via disc gel electrophoresis.
• Determination of molecular weight using gel filtration.
• Enzyme activity assays on various natural and synthetic substrates.

Main Results:

• A highly purified beta-D-mannosidase preparation was obtained from Polyporus sulfureus, exhibiting minimal alpha-mannosidase activity.
• The enzyme preparation showed a single band on disc gel electrophoresis, indicating high purity.
• The purified enzyme successfully hydrolyzed beta-D-mannopyranosyl units from diverse substrates, including glycopeptides and oligosaccharides.
• Molecular weight was estimated at approximately 64,000 Da, with optimal activity between pH 2.4-3.4 and a Km of 1.6 mM for p-nitrophenyl-beta-D-mannopyranoside.

Conclusions:

• Polyporus sulfureus is a valuable and unique source of highly purified beta-D-mannosidase.
• This enzyme is suitable for structural analysis of complex carbohydrates due to its specificity.
• The characterized properties provide a foundation for its application in glycobiology research.