Isolation and Inhibitory Activity of Angiotensin 1-Converting Enzyme Inhibitor in Enzymatic Hydrolyzates of Extracts from Skin and Bone of Croaker Argyrosomus argentatus

Inhibitors which inhibit the angiotensin l-converting enzyme (ACE) were prepared from trypsin digests of croaker extracts. The inhibitory activity of ACE detected in the trypsin degests of croaker extracts was fractionated into two major phosphopeptides fractions of P-1 and P-2 by gel filtration chromatography on sephadex G-50. The inhibition of ACE of the two kinds of phosphopeptides fractions of P-1 and P-2 was investigated in vitro. The IC_ values of p-1 and p-2 of phosphopeptides for ACE were 0.18 and 10.2mg protein/ml, respectively. In addition, the ACE inhibitor of P-1 and P-2 were further purified by ultrafiltration and by sephadex G-15 and G-25 chromatography. ACE inhibitory activity was fractionated into three major phosphopeptides fractions of P-1-1,P-1-2 and P-1-3 from the trypsin digests of the P-1,and into three major fractions of P-2-1,P-2-2 and P-2-3 from the trypsin digests of the P-2 by gel filtration rechromatography on sephadex G-15 and G-25,respectively. The inhibition of ACE of the six kinds of phosphopeptides fractions (P-1-1,P-1-2,P-1-3,P-2-1,P-2-2 and P-2-3) was analyzed in vitro. The IC_ values of P-1-1,P-1-2,P-1-3,P-2-1,P-2-2 and P-2-3 of phosphopeptides for ACE were 1.12,1.84,0.15,0.70,4.80 and 1.98mg protein/ml, respectively. The P-1-3 fraction had most inhibition activity and showed 0.15mg protein/ml inhibition against ACE at IC_ value. The amino acid compositions of the phosphopeptides fractions (P-1-1,P-1-2,P-1-3,P-2-1,P-2-2 and P-2-3) were characterized by relatively high percentage for Glu, Asp, Gly, Ala, Val, Leu, Tyr, Lys and Arg