Rapid purification and characterization of angiotensin I-converting enzyme from porcine lung.

Angiotensin I-converting enzyme (ACE) is a key target for screening hypertension medicines. However, traditional method for ACE preparation is time-consuming, and commercial ACE is expensive. In this study, a simple and effective method for ACE purification was proposed. ACE was purified to homogeneity from porcine lungs using acid precipitation, ammonium sulfate fractionation, and chromatography on a HiTrap Q HP column. 2D-PAGE showed that the molecular weight of ACE was 180 kDa, and the pI was 5.7, its sequence was verified by LC-MS/MS. The thermal denaturation temperature of ACE was 58.8 ± 0.4 °C and it is a glycoprotein as confirmed by PAS staining. Circular dichroism and endogenous fluorescence spectroscopy showed that the addition of zinc ions led to changes in the structure of ACE, thereby inhibiting its activity. Compared with commercial ACE, the enzyme prepared in the present study exhibited higher purity and 1.3-fold higher specific activity. As ACE is widely required for studies on anti-hypertensive functional foods, effective preparation of high-purity ACE will be valuable for the investigation of potential functional foods and especially its inhibitory peptides.