Production of functional peptides with inhibition ability against angiotensin I-Converting enzyme using P. pastoris expression system

To obtain the angiotension-I converting enzyme inhibitor (ACEI), a fusion ACEI polypeptide encoded with 8 DNA sequences of GPL, GPM, IKW, IVY, IRPVQ, IWHHT, IYPRY and IAPG, which were selected and designed and cloned into pGAPZαC and then transformed into Pichia pastoris SMD1168H. After 3 days induction, the fraction with highest ACEI activity was expressed and purified using a Ni Sepharose™ 6 Fast Flow. The IC(50) of recombinant ACEI polypeptide was 88.2 μM. A 128-fold increase of ACEI activity (0.69 μM) was obtained after pepsin digestion, which was equivalent to 0.022 μM of captopril. Reverse phase HPLC indicated all the 8 peptides contained in ACEI-hydrolysate after pepsin digestion.