Due to the unique structural features of heroin as well as the controlled interactions between functional monomers and the substrate homovanillic acid, a new type of catalytically active polymers was allowed to be well designed and prepared by molecular imprinting with hemin introduced as the catalytic center. Subsequent to a previous work on mimicking peroxidase by molecular imprinting techniques, this paper is focused on the regulating role of molecular recognition in substrate-binding and enzyme-like activity of the imprinted polymers, and a mechanistic elucidation was made on the catalytic reactions. The results demonstrated that the catalytic activity of the molecular imprinted polymers (MIP) was largely determined by substrate-binding sites and the molecular recognition process. Hemin was proven to not only serve as the catalytic center but also play an essential role in molecular recognition; the multiple-site interactions between the plural co-monomers and the substrate may overcome the interference of water molecules during molecular recognition and confer on the MIP an ideal substrate specificity toward template and catalytic activity even under aqueous conditions. (c) 2006 Elsevier B.V All rights reserved.