Inhibitory Activity of Angiotensin 1-Converting Enzyme of Phosphopeptides Obtained from Proteolytic Hydrolyzates of Oyster, Crassostrea gigas

In this investigation, the ACE inhibitory phosphopeptides of P-1 and C-2 were further purified by ultrafiltration and by Sephadex G-15 chromatography. ACE inhibitory activity was fractionated into three major phosphopeptides fractions of P-1-1, P-1-2 and P-1-3 in the pepsin hydrolyzates of the P-1, and into fractions of C-2-1, C-2-2 and C-2-3 in the pepsin hydrolyzates of the C-2 by gel filtration rechromatography on Sephadex G-15, respectively. The inhibition of ACE of the six kinds of phosphopeptides fractions (P-1-1, P-1-2, P-1-3, C-2-1, C-2-2 and C-2-3) was analyzed in vitro. The IC 50 values of P-1-1, P-1-2, P-1-3, C-2-1, C-2-2 and C-2-3 of phosphopeptides for ACE were 1.11, 0.04, 0.05, 1.04, 0.72 and 0.06 mg protein/ml, respectively. The P-1-2 fraction had the most inhibitory activity and showed 0.04 mg protein/ ml inhibition against ACE at IC 50 value. It has been demonstrated that the P-1-1, P-1-2, P-1-3, C-2-1, C-2-2 and C-2-3 contained about 23.2%, 4.4%, 28.1%, 2.0%, 3.8% and 1.6% as phosphonate-phosphorus of total phosphorus. The amino acid compositions of the phosphopeptides fractions (P-1-1, P-1-2, P-1-3, C-2-1, C-2-2 and C-2-3) were characterized by relatively high percentage for Glu, Asp, Gly, Ala, Val, Leu, Tyr, Phe, Lys and Arg. When the ACE inhibitory phosphopeptides were analyzed by thin layer chromatography, some ninhydrine-positive spots were observed. These results suggest that the phosphopeptides are a mixture of several phosphopeptides. The results above, the Sephadex G-15 gel filtration patterns of the active fraction obtained from the Sephadex G-50 column chromatography indicated that the