An antibody that is produced (e.g., via monoclonal antibody techniques) in response to a carefully selected antigen (i.e., one of the molecules involved in the chemical reaction that you are trying to catalyze). Such an antibody is then made to be catalytic by “attaching” a (molecular) group that is known to catalyze the desired chemical reaction. This attaching is done either via chemical modification of the antibody, or via genetic engineering of the cell (DNA) that produces that antibody.