Identification of angiotensin I-converting enzyme inhibitory peptides from enzymatic hydrolysates of pork loin

Figures & data

Figure 1. Flow chart for the isolation and identification of angiotensin I-converting enzyme (ACE) inhibitory peptides

Table 1. Degree of hydrolysis and ACE inhibitory activity of crude peptide extracts derived from pork loin injected with various enzymes

Treatment	Degree of hydrolysis (%)	ACE inhibitory activity (%)
Fresh	42 ± 2^b	49 ± 5^b
Control	35 ± 6^b	44 ± 11^b
E1	36 ± 3^b	52 ± 13^b
E2	97 ± 7^a	90 ± 7^a
E3	108 ± 12^a	93 ± 8^a

Fresh: un-injected pork, Control: pork injected with water, E1: pork injected with 100 ppm protease type XIII, E2: pork injected with 80 ppm thermolysin, E3: pork injected with a combination of 100 ppm protease type XIII and 80 ppm thermolysin.

^a,b Means ± SD in the same column with different superscript letters differ significantly (P < 0.05).

Figure 2. Absorbance at 220 nm and ACE inhibitory activity of gel-filtration fractions derived from thermolysin-injected pork loin (E2). The fractions were divided into four major groups (I–IV), and their ACE inhibitory activity was measured

Figure 3. (a) RP-HPLC profile and (b) ACE inhibitory activity of fraction E2-FIII. Peaks were divided into 17 groups (1–17), and their ACE inhibitory activity was measured

Figure 4. UPLC-QTOF-MS/MS analysis. Peptide with the sequence [(a) Leu-Val-Gly-Arg-Pro-Arg-His-Gly-Gln and (b) Val-Phe-Pro-Ser] of E2-FIII-P7

Table 2. ACE inhibitory activity (IC₅₀) of chemically synthesized peptides identified in thermolysin-injected pork loin

Peptide	Molecular weight	IC50 value^a
Leu-Val-Gly-Arg-Pro-Arg-His-Gly-Gln	1,019.6 Da^b	15.69 μM
Val-Phe-Pro-Ser	449.2 Da	3,606 mM
Captopril^c	217.29 Da	17.26 μM

^aThe IC₅₀ is the concentration of extract that inhibited 50% of the ACE activity.

^bDa: Dalton

^cCaptopril was used as positive control.