Angiotensin I-converting enzyme inhibitory peptides isolated from tofuyo fermented soybean food

Angiotensin I-converting enzyme (ACE) inhibitory activity was observed in a tofuyo (fermented soybean food) extract with an IC(50) value of 1.77 mg/ml. Two ACE inhibitors were isolated to homogeneity from the extract by adsorption and gel filtration column chromatography, and by reverse-phase high-performance liquid chromatography (HPLC). The purified substances reacted with 2,4,6-trinitrobenzensulfonic acid sodium salt. The amino acid sequences of these inhibitors determined by Edman degradation were Ile-Phe-Leu (IC(50), 44.8 microM) and Trp-Leu (IC(50), 29.9 microM). The Ile-Phe-Leu sequence is found in the alpha- and beta-subunits of beta-conglycinin, while the Trp-Leu sequence is in the B-, B1A- and BX-subunits of glycinin from soybean. Both of the peptides are non-competitive inhibitors. The inhibitory activity of Trp-Leu was completely preserved after a treatment with pepsin, chymotrypsin or trypsin. Even after successive digestion by these gastrointestinal proteases, the activity remained at 29% of the original value.     

Isolation and characterization of a novel angiotensin I-converting enzyme inhibitory peptide derived from the edible mushroom Tricholoma giganteum

The fruiting body of Tricholoma giganteum has many pharmaceutical uses and has long been utilized as a home remedy in Asia. This study describes the extraction and characterization of the first angiotensin I-converting enzyme (ACE) inhibitory peptide from T. giganteum. The maximum ACE inhibitory activity (IC50: 0.31 mg) was obtained when the fruiting body of T. giganteum was extracted with distilled water at 30 degrees C for 3 h. After the purification of ACE inhibitory peptides with ultrafiltration, Sephadex G-25 column chromatography, and reverse-phase HPLC, an active fraction with an IC50 of 0.04 mg and a yield of 0.3% was obtained. The ACE inhibitory peptide was a novel tripeptide, showing very low similarity to other ACE inhibitory peptide sequences, and was sequenced as Gly-Glu-Pro. The purified ACE inhibitor from T. giganteum competitively inhibited ACE, and it maintained inhibitory activity even after incubation with proteases. ACE inhibitor from T. giganteum showed a clear antihypertensive effect in spontaneously hypertensive rats (SHR), at a dosage of 1 mg/kg.     

Purification and characterization of angiotensin I converting enzyme inhibitory peptides from the rotifer, Brachionus rotundiformis

Angiotensin I converting enzyme (ACE) inhibitory peptide was isolated from the marine rotifer, Brachionus rotundiformis. ACE inhibitory peptides were separated from rotifer hydrolysate prepared by Alcalase, α-chymotrypsin, Neutrase, papain, and trypsin. The Alcalase hydrolysate had the highest ACE inhibitory activity compared to the other hydrolysates. The IC₅₀ value of Alcalase hydrolysate for ACE inhibitory activity was 0.63 mg/ml. We attempted to isolate ACE inhibitory peptides from Alcalase prepared rotifer hydrolysate using gel filtration on a Sephadex G-25 column and high performance liquid chromatography on an ODS column. The IC₅₀ value of purified ACE inhibitory peptide was 9.64 μM, and Lineweaver–Burk plots suggest that the peptide purified from rotifer protein acts as a competitive inhibitor against ACE. Amino acid sequence of the peptide was identified as Asp-Asp-Thr-Gly-His-Asp-Phe-Glu-Asp-Thr-Gly-Glu-Ala-Met, with a molecular weight 1538 Da. The results of this study suggest that peptides derived from rotifers may be beneficial as anti-hypertension compounds in functional foods resource.     

Analysis of novel angiotensin-I-converting enzyme inhibitory peptides from protease-hydrolyzed marine shrimp Acetes chinensis.

Acetes chinensis is an underutilized shrimp species thriving in the Bo Hai Gulf of China. In a previous study, we had used the protease from Bacillus sp. SM98011 to digest this kind of shrimp and found that the oligopeptide-enriched hydrolysate possessed antioxidant activity and high angiotensin I-converting enzyme (ACE) inhibitory activity with an IC50 value of 0.97 mg/ml. In this paper, by ultrafiltration, gel permeation chromatography and reversed-phase high-performance liquid chromatography (RP-HPLC), five peptides with high ACE inhibitory activity were purified from the shrimp hydrolysates and their sequences were identified by amino acid composition analysis and molecular weight (MW) analysis. Three of them, FCVLRP (a), IFVPAF (f) and KPPETV (j), were novel ACE inhibitory peptides. Their IC50 values were 12.3 microM, 3.4 microM and 24.1 microM, respectively, and their recoveries were 30 mg/100 g (solid basis of shrimp), 19 mg/100 g and 33 mg/100 g, respectively. Lineweaver-Burk plots for the three novel peptides showed that they are all competitive inhibitors. To test the ACE inhibitory activity of peptide a, f, j after they were digested by digestive enzymes in vivo, 12 derived peptides from FCVLRP and IFVPAF were synthesized based on their amino acid sequences and the cleavage sites of digestive enzymes. No digestive enzyme cleavage site was found in KPPETV. The IC50 values of the derived peptides were determined and the result showed that except for VPAF, FC and FCVL, the ACE inhibitory activity of the other nine derived peptides did not significantly change when compared with their original peptides. Surprisingly, five peptides had lower IC50 values than their original peptides, particularly for RP (IC50 value = 0.39 microM), which is about 30 times lower than its original peptide and almost the lowest IC50 value for ACE inhibitory peptides reported. Therefore, the novel peptides identified from A. chinensis hydrolysates probably still maintain a high ACE inhibitory activity even if they are digested in vivo. This is the first report about novel ACE inhibitory peptides from hydrolysates of marine shrimp A. chinensis. The novel peptides from hydrolysate of A. chinensis and some of their derived peptides with high ACE inhibitory activity probably have potential in the treatment of hypertension or in clinical nutrition.     

Characterization of new antihypertensive angiotensin I-converting enzyme inhibitory peptides from Korean traditional rice wine

This study describes the characterization of a new angiotensin I-converting enzyme (ACE) inhibitory peptide from a Korean traditional rice wine. After purification of the ACE inhibitor peptides with ultrafiltration, Sephadex G-25 column chromatography, and successively C?? and SCX solid-phase extraction, reverse-phase HPLC, and size exculsion chromatography, two types of the purified ACE inhibitors with IC?? values of 0.34 mg/ml and 1.23 mg/ml were finally obtained. The two purified ACE inhibitors (F-1 and F-2) were found to have two kinds of novel oligopeptides, showing very little similarity to other ACE inhibitory peptide sequences. The amino acid sequences of the two purified oligopeptides were found to be Gln- Phe-Tyr-Ala-Val (F-1) and Ala-Gly-Pro-Val-Leu-Leu (F-2), and their molecular masses were estimated to be 468.7 Da (F-1) and 357.7 Da (F-2), respectively. They all showed a clear antihypertensive effect on spontaneously hypertensive rats at a dosage of 500 mg/kg.     

Production of novel angiotensin I-converting enzyme inhibitory peptides by fermentation of marine shrimp <Emphasis Type="Italic">Acetes chinensis</Emphasis> with <Emphasis Type="Italic">Lactobacillus fermentum</Emphasis> SM 605

Acetes chinensis is an underutilized shrimp species thriving in Bo Hai Gulf of China. Its hydrolysate digested with protease SM98011 has been previously shown to have high angiotensin I-converting enzyme (ACE) inhibitory activity (He et al., J Pept Sci 12:726-733, 2006). In this article, A. chinensis were fermented by Lactobacillus fermentum SM 605 and the fermented sauce presented high ACE inhibitory activity. The minimum IC(50) value (3.37 +/- 0.04 mg/mL) was achieved by response surface methodology with optimized process parameters such as fermentation time of 24.19 h, incubation temperature at 38.10 degrees C, and pH 6.12. Three ACE inhibitory peptides are purified by ultrafiltration, gel filtration, and reverse-phase high performance liquid chromatography. Identified by mass spectrometry, their amino acid sequences are Asp-Pro, Gly-Thr-Gly, and Ser-Thr, with IC(50) values of 2.15 +/- 0.02, 5.54 +/- 0.09, and 4.03 +/- 0.10 microM, respectively. Also, they are all novel ACE inhibitory peptides. Compared with protease digestion, fermentation is a simpler and cheaper method to produce ACE inhibitory peptides from shrimp A. chinensis.     

Latent production of angiotensin I-converting enzyme inhibitors from buckwheat protein.

The latent production of angiotensin I-converting enzyme (ACE) Inhibitors from tartary buckwheat (BW) was investigated, and the peptides responsible for ACE inhibition characterized. Intact buckwheat was found to exhibit ACE inhibitory activity having an IC50 value of 3.0 mg/ml. The activity of the protein fraction (IC50: 0.36 mg protein/ml) was not enhanced by pepsin treatment. Pepsin, followed by chymotrypsin and trypsin hydrolysis, resulted in a significant increase in the ACE inhibitory activity (IC50: 0.14 mg protein/ml). The rutin contained in the buckwheat did not exhibit any ACE inhibition. A single oral administration of BW digest lowered the systolic blood pressure of a spontaneously hypertensive rat. Thus, BW proteins offer a potential resource for producing ACE inhibitory peptides during the digestion process. From the di-/tri-peptide fraction (DTPF) of the BW digest, inhibitory peptides were identified. The magnitude (%) of the total ACE inhibitory contribution of each identified peptide, relative to the overall inhibition of the DTPF, was about 41%.     

Antihypertensive effect and purification of an ACE inhibitory peptide from sea cucumber gelatin hydrolysate

Gelatin from the sea cucumber (Acaudina molpadioidea) was hydrolyzed sequentially with bromelain and alcalase. The hydrolysate was fractionated into three ranges of molecular weight (GH-I, <10 kDa; GH-II, <5 kDa; GH-III, <1 kDa) using an ultrafiltration membrane bioreactor system. The GH-III brought about a high angiotensin-I-converting enzyme (ACE) inhibitory activity, with IC₅₀ value of 0.35 mg/ml. An ACE inhibitory peptide was isolated from the GH-III, using the chromatographic methods including ion-exchange chromatography, gel filtration and reversed phase high-performance liquid chromatography. The purified ACE inhibitory peptide with a molecular weight of 840 Da consisted of five main amino acids (Glu, Asp, Pro, Gly and Ala), and its IC₅₀ value was 0.0142 mg/ml. This sea cucumber gelatin hydrolysate (GH-III) was used as drinks administered to renal hypertensive rats (RHR) for 1 month. The systolic blood pressure and diastolic blood pressure of the RHR were significantly reduced, which indicates an antihypertensive effect by oral administration.     

Production of angiotensin-I-converting-enzyme-inhibitory peptides in fermented milks started by Lactobacillus delbrueckii subsp. bulgaricus SS1 and Lactococcus lactis subsp. cremoris FT4

Two fermented milks containing angiotensin-I-converting-enzyme (ACE)-inhibitory peptides were produced by using selected Lactobacillus delbrueckii subsp. bulgaricus SS1 and L. lactis subsp. cremoris FT4. The pH 4.6-soluble nitrogen fraction of the two fermented milks was fractionated by reversed-phase fast-protein liquid chromatography. The fractions which showed the highest ACE-inhibitory indexes were further purified, and the related peptides were sequenced by tandem fast atom bombardment-mass spectrometry. The most inhibitory fractions of the milk fermented by L. delbrueckii subsp. bulgaricus SS1 contained the sequences of beta-casein (beta-CN) fragment 6-14 (f6-14), f7-14, f73-82, f74-82, and f75-82. Those from the milk fermented by L. lactis subsp. cremoris FT4 contained the sequences of beta-CN f7-14, f47-52, and f169-175 and kappa-CN f155-160 and f152-160. Most of these sequences had features in common with other ACE-inhibitory peptides reported in the literature. In particular, the beta-CN f47-52 sequence had high homology with that of angiotensin-II. Some of these peptides were chemically synthesized. The 50% inhibitory concentrations (IC(50)s) of the crude purified fractions containing the peptide mixture were very low (8.0 to 11.2 mg/liter). When the synthesized peptides were used individually, the ACE-inhibitory activity was confirmed but the IC(50)s increased considerably. A strengthened inhibitory effect of the peptide mixtures with respect to the activity of individual peptides was presumed. Once generated, the inhibitory peptides were resistant to further proteolysis either during dairy processing or by trypsin and chymotrypsin.     

Casein fermentate of Lactobacillus animalis DPC6134 contains a range of novel propeptide angiotensin-converting enzyme inhibitors

This work evaluated the angiotensin-converting-enzyme (ACE)-inhibitory activities of a bovine sodium caseinate fermentate generated using the proteolytic capabilities of the porcine small intestinal isolate Lactobacillus animalis DPC6134 (NCIMB deposit 41355). The crude 10-kDa L. animalis DPC6134 fermentate exhibited ACE-inhibitory activity of 85.51% (+/-15%) and had a 50% inhibitory concentration (IC50) of 0.8 mg protein/ml compared to captopril, which had an IC50 value of 0.005 mg/ml. Fractionation of the crude L. animalis DPC6134 fermentate by membrane filtration and reversed-phase high-performance liquid chromatography (HPLC) generated three bioactive fractions from a total of 72 fractions. Fractions 10, 19, and 43 displayed ACE-inhibitory activity percentages of 67.53 (+/-15), 83.71 (+/-19), and 42.36 (+/-11), respectively, where ACE inhibition was determined with 80 microl of the fractions with protein concentrations of 0.5 mg/ml. HPLC and mass spectrometry analysis identified 25 distinct peptide sequences derived from alpha-, beta-, and kappa-caseins. In silico predictions, based on the C-terminal tetrapeptide sequences, suggested that peptide NIPPLTQTPVVVPPFIQ, corresponding to beta-casein f(73-89); peptide IGSENSEKTTMP, corresponding to alpha(s1)-casein f(201212); peptide SQSKVLPVPQ, corresponding to beta-casein f(166-175); peptide MPFPKYPVEP, corresponding to beta-casein f(124133); and peptide EPVLGPVRGPFP, corresponding to beta-casein f(210-221), contained ACE-inhibitory activities. These peptides were chosen for chemical synthesis to confirm the ACE-inhibitory activity of the fractions. Chemically synthesized peptides displayed IC50 values in the range of 92 microM to 790 microM. Additionally, a simulated gastrointestinal digestion confirmed that the ACE-inhibitory 10-kDa L. animalis DPC6134 fermentation was resistant to a cocktail of digestive enzymes found in the gastrointestinal tract.     

The antihypertensive activity of angiotensin-converting enzyme inhibitory peptide containing in bovine lactoferrin

Angiotensin I-converting enzyme (ACE) inhibitory peptide was isolated from the bovine lactoferrin hydrolysate using peptic hydrolysis by 2-step of reverse-phase high-performance liquid chromatography. This peptide was identified as Leu-Arg-Pro-Val-Ala-Ala and it produced a concentration-dependent inhibition of ACE activity in vitro with an IC50 value of about 4.14 microM. Also, this inhibition was identified as noncompetitive from the Lineweaver-Burk plot. Moreover, the antihypertensive activity of Leu-Arg-Pro-Val-Ala-Ala was investigated by the intravenous injection into spontaneously hypertensive rats (SHRs). A dose-dependent reduction of systolic blood pressure by this peptide was observed at 60 min after injection and it maximally decreased the blood pressure at a rate of 1 nmol/ml/kg. The blood pressure lowering activity of this peptide was calculated as 210% of captopril (10 pmol/ml/kg) that was used as positive control. Otherwise, identification of this peptide in the blood of SHRs was carried out chromatographically. Reduction of blood pressure coincides with the peak peptide concentration in the serum. Thus, we conclude that this peptide inhibits ACE activity in vitro and lowers systolic blood pressure in spontaneously hypertensive rat.     

Anticancer activity of hydrophobic peptides from soy proteins

An anticancer peptide from soy protein was purified and isolated. Defatted soy protein was hydrolyzed with thermoase and hydrophobic peptides were extracted with ethanol. The peptide extract was fractionated by XAD-2 hydrophobic, gel filtration chromatography, and different C18 HPLCs. Anticancer activity of each fraction was assayed by measuring in vitro cytotoxicity on P388D1, a mouse monocyte macrophage cell line. IC50 value of a peptide fraction from Sephadex G-25 chromatography was 0.16 mg/ml. This peptide fraction at 1 mg/ml significantly affected cell cycle progression by arresting P388D1 at G2/M phases. Finally purified peptide from analytical C18 HPLC was nonapeptide of which molecular weight was 1157 Da and the sequence was X-Met-Leu-Pro-Ser-Tye-Ser-Pro-Tyr.     

Purification and identification of novel angiotensin-I converting enzyme (ACE) inhibitory peptides from cultured marine microalgae (Nannochloropsis oculata) protein hydrolysate

Isolation of bioactive compounds and commercialization of marine microalgae sources are interesting targets in future marine biotechnology. Cultured biomass of the marine microalga, Nannochloropsis oculata, was used to purify angiotensin-I converting enzyme (ACE) inhibitory peptides using proteases including pepsin, trypsin, α-chymotrypsin, papain, alcalase, and neutrase. The pepsin hydrolysate exhibited the highest ACE inhibitory activity, compared to the other hydrolysates and then was separated into three fractions (F1, F2, and F3) using Sephadex G-25 gel filtration column chromatography. First fraction (F1) showed the highest ACE inhibitory activity and it was further purified into two fractions (F1-1 and F1-2) using reverse-phase high-performance liquid chromatography. The IC₅₀ value of purified ACE inhibitory peptides were 123 and 173 μM and identified as novel peptides, Gly-Met-Asn-Asn-Leu-Thr-Pro (GMNNLTP; MW, 728 Da) and Leu-Glu-Gln (LEQ; MW, 369 Da), respectively. In addition, nitric oxide production level (%) was significantly increased by the purified peptide (Gly-Met-Asn-Asn-Leu-Thr-Pro) compared to the purified peptide (Leu-Glu-Gln) and other treated pepsin hydrolysate fractions on human umbilical vein endothelial cells (HUVECs). Cell viability assay showed no cytotoxicity on HUVECs with the treated purified peptides and fractions. These results suggest that the isolated peptides from cultured marine microalga, N. oculata protein sources may have potentiality to use commercially as ACE inhibitory agents in functional food industry.     

Novel angiotensin I-converting enzyme inhibitory peptides isolated from Alcalase hydrolysate of mung bean protein.

Mung bean protein isolates were hydrolyzed for 2 h by Alcalase. The generated hydrolysate showed angiotensin I-converting enzyme (ACE) inhibitory activity with the IC(50) value of 0.64 mg protein/ml. Three kinds of novel ACE inhibitory peptides were isolated from the hydrolysate by Sephadex G-15 and reverse-phase high performance liquid chromatography (RP-HPLC). These peptides were identified by amino acid composition analysis and matrix assisted-laser desorption/ionization time-of-flight tandem mass spectrometry (MALDI-TOF MS/MS), as Lys-Asp-Tyr-Arg-Leu, Val-Thr-Pro-Ala-Leu-Arg and Lys-Leu-Pro-Ala-Gly-Thr-Leu-Phe with the IC(50) values of 26.5 microM, 82.4 microM and 13.4 microM, respectively.     

A quantitative in silico analysis calculates the angiotensin I converting enzyme (ACE) inhibitory activity in pea and whey protein digests

Angiotensin I converting enzyme (ACE) inhibitory peptides can induce antihypertensive effects after oral administration. By means of an ACE inhibitory peptide database, containing about 500 reported sequences and their IC(50) values, the different proteins in pea and whey were quantitatively evaluated as precursors for ACE inhibitory peptides. This analysis was combined with experimental data from the evolution in ACE inhibitory activity and protein degradation during in vitro gastrointestinal digestion. Pea proteins produced similar in silico scores and were degraded early in the in vitro digestion. High ACE inhibitory activity was observed after the simulated stomach phase and augmented slightly in the simulated small intestine phase. The major whey protein beta-lactoglobulin obtained the highest in silico scores, which corresponded with the fact that degradation of this protein in vitro only occurred from the simulated small intestine phase on and resulted in a 10-fold increase in the ACE inhibitory activity. Whey protein obtained total in silico scores of about 124 ml/mg, compared to 46 ml/mg for pea protein, indicating that whey protein would be a richer source of ACE inhibitory peptides than pea protein. Although beta-lactoglobulin is only partially digested, a higher ACE inhibitory activity was indeed found in the whey (IC(50) = 0.048 mg/ml) compared to the pea digest (IC(50) = 0.076 mg/ml). In silico gastrointestinal digestion of the highest scoring proteins in pea and whey, vicilin and albumin PA2, and beta-lactoglobulin, respectively, directly released a number of potent ACE inhibitory peptides. Several other ACE inhibitory sequences resisted in silico digestion by gastrointestinal proteases. Briefly, the quantitative in silico analysis will facilitate the study of precursor proteins on a large scale and the specific release of bioactive peptides.     

Kenojeinin I, antimicrobial peptide isolated from the skin of the fermented skate, Raja kenojei

An antimicrobial peptide was purified from fermented skate skin extract using the solid-phase extraction and separation on HPLC reversed-phase chromatography. Amino acid sequence of the purified peptide (Peak A) having an antimicrobial activity revealed the presence of many cationic residues of the total 28 amino acids. Its molecular mass was found to be 3059 Da. This result was in excellent agreement with the theoretical molecular mass calculated from the amino acid sequence. The synthetic kenojeinin I had inhibitory effects on B. subtilis (MIC, 12 microg/ml), E. coli (28 microg/ml), and S. cerevisiae (12 microg/ml). These results indicate that fermented skate skin is potentially antimicrobial.     

Purification and characterization of angiotensin I-converting enzyme inhibitory peptide from enzymatic hydrolysates of Styela clava flesh tissue

Angiotensin I-converting enzyme (ACE) inhibitory peptide was isolated from the Styela clava flesh tissue. Nine proteases (Protamex, Kojizyme, Neutrase, Flavourzyme, Alcalase, pepsin, trypsin, α-chymotrypsin and papain) were used, and their respective enzymatic hydrolysates and an aqueous extract were screened to evaluate their potential ACE inhibitory activity. Among all of the test samples, Protamex hydrolysate possessed the highest ACE inhibitory activity, and the Protamex hydrolysate of flesh tissue showed relatively higher ACE inhibitory activity compared with the Protamex hydrolysate of tunic tissue. We attempted to isolate ACE inhibitory peptide from the Protamex hydrolysate of S. clava flesh tissue using ultrafiltration, gel filtration on a Sephadex G-25 column and high performance liquid chromatography (HPLC) on an ODS column. The purified ACE inhibitory peptide exhibited an IC₅₀ value of 37.1 μM and was identified as non-competitive inhibitor of ACE. Amino acid sequence of the peptide was identified as Ala-His-Ile-Ile-Ile, with a molecular weight 565.3 Da. The results of this study suggested that the peptides derived from enzymes-assisted extracts of S. clava would be useful new antihypertension compounds in functional food resource.     

Purification and identification of adipogenesis inhibitory peptide from black soybean protein hydrolysate

Adipogenesis inhibitory peptide was isolated and identified from black soybean (Rhynchosia volubilis Lour.) hydrolysate. An adipogenesis inhibitor was purified using consecutive methods including: ultrafiltration (MWCO; 3 and 10kDa), gel filtration chromatography (Superdex Peptide 10/300 GL column), and reverse-phase high-performance liquid chromatography (microBondapak C(18) column). Also, the adipogenesis inhibition effect of the purified peptide was measured by observation of droplet of 3T3-L1 adipocyte by Oil Red O staining in the highest active fraction in each step. The peptide was shown to inhibit the differentiation of the 3T3-L1 pre-adipocyte, which was confirmed by morphological study. The adipogenesis inhibitory peptide was purified 71.43-fold from black soybean hydrolysate throughout a five-step purification procedure. The adipogenesis inhibitor was identified to be a tripeptide, Ile-Gln-Asn, having an IC(50) value of 0.014 mg protein/ml. Furthermore, the synthetic tripeptide (Ile-Gln-Asn) exhibited the similar adipogenesis effects to the purified peptide. Thus, these results showed the potential anti-obesity effect of the purified peptide through control of adiposity.     

High throughput and rapid screening of marine protein hydrolysates enriched in peptides with angiotensin-I-converting enzyme inhibitory activity by capillary electrophoresis

Twelve kinds of marine protein materials, including fish, shrimp, seashell, algae and seafood wastes were selected for the hydrolysis using four different proteases. The IC(50) values for angiotensin-converting enzyme (ACE) inhibitory activity of 48 hydrolysates were rapidly determined by capillary electrophoresis (CE). The values ranged from 0.17 to 501.7mg/ml, and were affected by both the marine protein resources and the selected proteases. Hydrolysates of the lowest IC(50) values were from shrimp (Acetes chinensis), shark meat, mackerel bone, Polysiphonia urceolata and Spirulina platensis, indicating these five kinds of marine food proteins contained beneficial materials for the production of ACE inhibitory peptides by proteolysis. The hydrolysates obtained using proteases Protamex and SM98011 had lower IC(50) values, showing these two proteases were superior to others. The CE method achieved the same sensitivity as the high performance liquid chromatography (HPLC) method. However, the CE method was faster and, as a result, more economical. Therefore, CE had potential for rapid screening of marine protein hydrolysates enriched in ACE inhibitory peptides.     

Angiotensin converting enzyme inhibitory pentapeptide isolated from supernatant of pig plasma treated by trichloroacetic acid

Summary Angiotensin converting enzyme (ACE) inhibitory peptide was isolated from supernatant of trichloroacetic acid treated pig plasma using gel filtration chromatography and reverse phase high pressure liquid chromatography. Protein sequencing showed that the peptide is a pentapeptide of Gly-Val-His-Gly-Val with 2 M as IC₅₀ value.