With combinative functionalities as well as the improved activity and stability, the novel hybrid enzymes (HEs) from the heterogeneous enzymes of a-aspartyl dipeptidase (PepE, monomer) and L-aspartase (L-AspA, tetramer) were constructed successfully by gene random deletion strategy. The wild-type hybrid enzyme (WHE) and the evolved hybrid enzyme (EHE) were selected, respectively, upon the phenotype and the enzyme activity. The relative activity of the WHE tested was about 110% of the wild-type PepE and 26% of the wild-type L-AspA, whilst the activity of EHE was about 340% of the PepE and 87% of the L-AspA. In comparison to its individual wild-type enzymes, the EHE exhibited an improved thermostability, when examined at the enzyme concentration of 10-7 mol/L, but the WHE showed a reduced thermostability. The activity of the EHE was about 3-fold compared to that of the WHE. The current results give a good example that the hybridization of enzymes could be attained between the monomer and multimer enzymes. In addition, they also indicate that construction hybrid enzyme from evolved enzymes is feasible. 2005 Elsevier Inc. All rights reserved.