Aim: To prepare a recombinant insulin-degrading enzyme by means of prokarocytes expression, and analyze its activity. Methods: The experiment was carried out in the Research Room of Neurobiology, Beijing Institute of Geriatrics from May to November 2004. The cDNA encoding rat insulin degrading enzyme (rIDE) was subcloned into the plasmid pGEX-4T-1 and a glutathione S transferase (GST)-tagged rIDE was expressed with bacteria BL21. Recombinant rIDE was released from fusion protein by thrombin, and purified with glutathione sepharose 4B affinity column chromatography. The activity of the recombinant ride was detected with high-pressure liquid chromatography. Results: 1 The subcloning of rIDE cDNA coding region segment: The cDNA segment of recombinant plasmid cloning was 3 060 bp, coding was 1 019 amino acid. 2 The expression and purification of rIDE in prokarocytes: The recombinant rIDE was expressed in the soluble fraction of the bacteria proteins. The overall yield of the recombinant enzyme was approximately 0.5 mg/L from one liter of bacterial culture. The single band corresponded to a protein of 110 000 on SDS-PAGE, as expected from the predicted amino acid sequence. 3 The degradation of recombinant protein on insulin: The elusion peaks of beef insulin and recombinant protein occurred at 34.5 and 38.3 minutes respectively. After the purified recombinant protein and insulin were co-incubated at 37 °C, the insulin content was obviously decreased. The mass changed obviously in the first 20 minutes of incubation, the value of peak area decreased by about 50%, but the degradation at other times were not obvious. The protein had no degradation to the two subtypes of 14-3-3 protein. Conclusion: Recombinant rIDE has the activity of natural enzyme, but the activity is postponed after 20-minute incubation. The degradation product feed back of insulin inhibits the rIDE activity, which is correlated with the self-regulation of enzyme. The recombinant rIDE with biological activity was prepared in the study, which has laid a foundation for the further preparation of anti-insulin-degrading enzyme monoclonal antibody and the exploration of the correlation between insulin-degrading enzyme and type 2 diabetes mellitus.