Abzyme

An abzyme (from antibody and enzyme), also called catmab (from catalytic monoclonal antibody), is a monoclonal antibody with catalytic activity. Abzymes are usually artificial constructs, but are also found in normal humans (anti-vasoactive intestinal peptide autoantibodies) and in patients with the autoimmune disease systemic lupus erythematosus, where they can bind and hydrolyze DNA. Abzymes are potential tools in biotechnology, e.g., to perform specific actions on DNA.

Enzymes function by stabilizing an otherwise-less-favorable molecular intermediate between reactants and products. If an antibody is developed to a stable molecue that's similar to an unstable intermediate of another (potentially unrelated) reaction, the developed antibody will enzymatically favor the intermediate state, thus catalyzing the reaction.