Isolation of angiotensin I-converting enzyme inhibitor from pepsin hydrolysate of porcine hemoglobin

Abstract

Angiotensin I-converting enzyme (ACE) inhibitors have been widely used as antihypertensive agents. However, most synthetic ACE inhibitors ineluctably have severe side effects. Researchers have focused on various ACE-inhibitory peptides derived from dietary food. In the present study, we reported peptides produced from porcine blood, an important food in Asian countries. Through enzymatic hydrolysis, we found that peptides from this animal compound have ACE-inhibitory effects. Porcine hemoglobin was hydrolyzed using ordinary proteases, including alcalase, trypsin, neutral, papain, protamex, and pepsin. Results showed that pepsin was the most efficient protease in producing active peptides, and the pepsin hydrolysate of porcine hemoglobin showed the highest activity (IC50 = 1.53 ± 0.03 mg/mL). Combining DA 201-C macroporous resin chromatography, Sephadex LH-20 gel chromatography, and reversed-phase high-performance liquid chromatography, the fraction 2-IV was purified from pepsin hydrolysis of porcine hemoglobin; this compound exhibited the highest ACE-inhibitory activity (IC50 = 0.02 ± 0.01 mg/mL). Through Edman degradation, we also found that the exact amino acid sequence of fraction 2-IV was Gln–Glu–Leu–Pro–Gly. The results indicated that porcine hemoglobin peptides possessed significant ACE-inhibitory effect in vitro, which is an important complement of the previous work.