New bioactive peptides with antihypertensive property from red blood corpuscle (RBC) and plasma (PL) hydrolysate fractions of porcine blood were identified. Three peptides with the highest Angiotensin-converting enzyme (ACE) inhibitory activity from RBC, including RBC7 (TPYPCV), RBC15 (VVYPWR) and RBC9 (FLCT), showed IC 50 values of 2.58 AE 0.87, 5.22 AE 2.56 and 6.53 AE 0.34 µM, respectively. By comparison, PL1 (YTFPFH), PL2 (WGHGNPHV) and PL7 (VPLW) from PL displayed higher IC 50 values at 24.12 AE 2.44, 15.33 AE 0.44 and 32.80 AE 38.96 µM, respectively. Molecular docking was employed to simulate the interactions of RBC7 and RBC15 with the catalytic site of the ACE receptor. RBC7 and RBC15 interacted with residues in the ACE receptor that normally coordinated with Zn(II), and RBC7 also interacted extensively with residues within S1, S2 and S'1 active sites. Taken together, these results illustrate that porcine blood is an excellent source of antihypertensive peptides and could be of great benefits to people with high blood pressure.

Dissolve Enzyme B in 2 ml of deionized water to prepare Enzyme B solution. Then add 1.5 ml of Enzyme B solution to Enzyme A to prepare Enzyme working solution.Note: Enzyme A and B vials are capped under vacuum pressure. Add deionized water or solution through the rubber septum with a syringe, and then remove the septum. Note: The Enzyme working solution is stable at −20 °C for 2 weeks or in a refrigerator for 3 days. Indicator working solution:Dissolve Enzyme C and Coenzyme in 3 ml of deionized water each. Add 2.8 ml of Enzyme C solution and 2.8 ml of Coenzyme solution to Indicator solution to prepare Indicator working solution.Note: Enzyme C and Coenzyme vials are capped under vacuum pressure. Add deionized water through the rubber septum with a syringe, and then remove the septum. Note: The Indicator working solution is stable at −20 °C for 2 weeks or in a refrigerator for 3 days.