We have used the imprinting technique to create a polymer/organo-smectite nanocomposite catalyst. The aim was preparing a synthetic enzyme which shows high selectivity for paraoxon hydrolysis. Paraoxon imprinted polymer/organo-smectite composites (PIPO) and non-imprinted polymer/organo-smectite composites (NIPO) were prepared using methacryloylhistidine-Cu2+ (MAH-Cu(II)) and [2-methacryloyloxy)ethyl]dimethylhexadecylammonium bromide] (MOEDMAC(16)) modified smectite. These nanocomposites were applied as a catalyst in the hydrolysis of paraoxon which is an organophosphate ester and used as a pesticide. The catalytic activity of these composites was evaluated according to the enzyme kinetics model of Michaelis-Menten. PIPO showed better catalytic activity than NIPO. In addition, the paraoxon imprinted nanocomposite had greater catalytic activity (based on k(cat)/K-m values) for paraoxon hydrolysis by a factor of 391 compared to that of parathion hydrolysis. (C) 2009 Elsevier B.V. All rights reserved.