The objectives of this study were to obtain the combinatorial libraries in water and reverse micellar systems and to evaluate their catalytic activity applying the reverse micelles as microreactors under the restrictions of size and conformation. The amino acids, viz., Gly, Asp, His, Arg, and Leu were selected for polypeptide synthesis based on the reported bioinformatic approaches. The polypeptides were synthesized by carbodiimide method. The activity was defined as an increase in absorbance after 15 min of reaction with reference to control without amino acids using ABTS, catechol, and pyrogallol as the substrates for oxidase activity, ABTS/H2O2 as the substrates for peroxidase activity, and NIPAB as the substrate for hydrolase activity, with and without Zn2+, Cu2+, Mn2+ sulfates and hemin. The evidence of catalytic activity was observed in the synthesized combinatorial libraries. The presence of polypeptide chains was demonstrated by electrophoresis. © 2007 by Allerton Press, Inc.