Expression of milk-derived antihypertensive peptide in Escherichia coli

Many angiotensin converting enzyme inhibitory peptides (ACEIP) have been identified in recent years. Among all the literatures available thus far, almost all the ACEIP were obtained by means of enzymatic hydrolysis. However, little information was available on antihypertensive peptides obtained by DNA recombination technology. In the present paper, our aims were 1) to establish a new method to produce antihypertensive peptides (AHP), and 2) to study the expression profiles of different host strains (Escherichia coli JM109 and DH5alpha). To achieve these objectives, a DNA fragment encoding the published ACEIP, identified as FFVAPFPEVFGK (known as CEI12) was synthesized, ligated with the expression vector, pQE16, and transformed into E. coli JM109 and DH5alpha. SDS-PAGE analysis and Western-blotting detection demonstrated that the peptide CEI12 (fused with dihydrofolate reductase [DHFR]) was specifically expressed only in E. coli JM109 with IPTG induction. The expression profiles of the AHP CEI12 at different IPTG concentrations and different inducing times demonstrated no significant differences by SDS-PAGE analysis. The expression level of CEI12 (fused with DHFR) was about 500 microg/L culture.