Peptides with angiotensin I-converting enzyme (ACE) inhibitory activity from defibrinated hydrolyzed bovine plasma

Defibrinated bovine plasma (DBP) was treated with the microbial protease Flavourzyme to obtain protein hydrolysates with various degrees of hydrolysis: (DH). The angiotensin I-converting,enzyme (ACE) inhibiting activity of the hydrolyzed protein was assessed with hippuryl-His-Leu as the substrate.. The amount of hippuric acid released, due to uninhibited-ACE activity, was determined by high-performance liquid chromatography. ACE inhibiting (ACEI) activity was found to increase with a. increasing DH; the 43% DH hydrolysate exhibited the highest activity and had an IC50 of 1.08 mg/mL. Peptide fractions with high ACEI activity were isolated using size exclusion chromatography. The fraction that possessed the highest ACEI activity contained peptides,with GYP, HL(I), HPY, HPGH, L(I)F, SPY; and YPH sequence motifs, as determined by reversed-phase liquid chromatography-tandem mass spectrometry using a novel immonium precursor-ion scanning technique. Some of these motifs correspond to,sequences found in bovine serum albumin, a potential source of ACEI peptides in bovine plasma.