alpha-Mannosidase activity from antibody raised against a glucal antigen

Area of Science:

• Biochemistry
• Immunology
• Enzymology

Background:

• Monoclonal antibodies are crucial tools in biological research.
• Enzyme-mimicking antibodies (abzymes) offer unique catalytic properties.

Purpose of the Study:

• To develop and characterize monoclonal antibodies with enzymatic activity.
• To investigate the catalytic mechanism of an abzyme with alpha-mannosidase activity.

Main Methods:

• Generation of 60 monoclonal antibody cell lines against a glucal hapten.
• Assay of alpha-mannosidase activity for selected antibodies.
• Chemical modification and pH profile studies of the antibody.

Main Results:

• Antibody Ab 405.4 displayed significant alpha-mannosidase activity (kcat = 0.19/day).
• The catalytic efficiency (kcat/kuncat) was determined to be 110,000.
• Studies indicated the involvement of carboxyl group(s) in the antigen-binding site during catalysis.

Conclusions:

• Monoclonal antibody Ab 405.4 functions as an effective alpha-mannosidase.
• The antigen-binding site's carboxyl groups are integral to the antibody's catalytic mechanism.
• This abzyme provides a model for understanding antibody-based catalysis.