The potent anti-hypertensive peptide, RPLKPW, has been designed based on the structure of ovokinin(2–7). The sequence encoding this peptide was introduced into three homologous sites in the gene for soybean β-conglycinin α′ subunit. The native α′ subunit as well as the modified, RPLKPW-containing α′ subunit were expressed in Escherichia coli, recovered from the soluble fraction and then purified by ion-exchange chromatography. The RPLKPW peptide was released from recombinant RPLKPW-containing α′ subunit after in vitro digestion by trypsin and chymotrypsin. Moreover, the undigested RPLKPW-containing α′ subunit given orally at a dose of 10 mg/kg exerted an anti-hypertensive effect in spontaneously hypertensive rats, unlike the native α′ subunit. These results provide evidence for the first time that a physiologically active peptide introduced into a food protein by site-directed mutagenesis could practically function in vivo even at a low dose.
