Preparation of angiotensin I converting enzyme inhibitor from corn gluten

Enhancement of functional properties, digestive properties, and in vitro digestion product physiological activity of extruded corn gluten meal by enzymatic modification

BACKGROUND

Enzymatic modification is an effective means of improving the functional properties, digestive properties, and in vitro digestion product physiological activity of proteins, thus significantly expanding protein uses in various food applications.

RESULTS

In this study, the addition of chymotrypsin (CT) at pH 9.0 and 11.0 was found to significantly improve the functional properties (solubility, foaming properties, water holding capacity, oil holding capacity, etc.) and digestive properties of extruded corn gluten meal (ECGM). Similar changes were observed when treating ECGM with glutaminase, protein glutaminase, and papain. These changes were likely due to the increase in number of carboxyl groups and the multiple effects of change in protein net charge and conformation caused by enzymatic deamidation. Of note, ECGM deamidated by CT showed the highest degree of deamidation, solubility, and gastrointestinal digestibility at pH 11.0, up to 44.92%, 43.75%, and 82.22%, respectively. In addition, CT-ECGM digestion product exhibited strong antioxidant activity and potential to promote alcohol metabolism in both a static digestion model and dynamic digestion model, even comparable to commercial corn peptides (CCP), while being inexpensive and of low bitterness compared to CCP. Meanwhile, the physiological activity enhanced as the molecular weight of digestion product decreased with the digested component having strongest activity.

CONCLUSION

This study may promote the application of ECGM as a food component in the food industry or even as a substitute for CCP. © 2023 Society of Chemical Industry.

Ultrasound-Assisted Multi-Enzymatic System for the Preparation of ACE Inhibitory Peptides with Low Bitterness from Corn Gluten Meal

The promising angiotensin converting enzyme (ACE) inhibitory peptides derived from corn protein usually have strong bitterness and thus limit their use among consumers. To prepare ACE inhibitory peptides with low bitterness, two energy-efficient types of ultrasound pretreatment were introduced into the multi-enzymatic system of corn gluten meal. The results showed that Flavourzyme–Protamex sequential enzymolysis produced the peptides with high ACE inhibitory activity and the lowest bitterness compared with other enzymolysis conditions. During the optimized sequential enzymolysis, the divergent ultrasound pretreatment with a frequency of 40 kHz for 60 min exhibited higher ACE inhibitory activity (65.36%, accounting for 73.84% of the highest ACE inhibitory activity) and lower bitterness intensity of peptides, compared with an energy-gathered ultrasound. The results of the study showed that, on the one hand, divergent ultrasound pretreatment induced the highest intrinsic fluorescence of protein, with more hydrophobic amino acid residues exposed for cleavage by exopeptidases, which leads to a reduction in bitterness. On the other hand, the amino acid composition analysis proved that more Tyr, Ile, and Val moieties, instead of Leu (bitterest substance), and more peptide fractions with a molecular weight >1000 Da should be the structural features of high ACE inhibitory peptides.

Marine Organisms as Potential Sources of Bioactive Peptides that Inhibit the Activity of Angiotensin I-Converting Enzyme: A Review

Angiotensin I-converting enzyme (ACE) is a paramount therapeutic target to treat hypertension. ACE inhibitory peptides derived from food protein sources are regarded as safer alternatives to synthetic antihypertensive drugs for treating hypertension. Recently, marine organisms have started being pursued as sources of potential ACE inhibitory peptides. Marine organisms such as fish, shellfish, seaweed, microalgae, molluscs, crustaceans, and cephalopods are rich sources of bioactive compounds because of their high-value metabolites with specific activities and promising health benefits. This review aims to summarize the studies on peptides from different marine organisms and focus on the potential ability of these peptides to inhibit ACE activity.

Functions and Applications of Bioactive Peptides From Corn Gluten Meal

Corn protein has been identified as an important source of bioactive peptides. Such peptides can be released during hydrolysis induced by proteolytic enzymes or microbial fermentation. Corn peptides have been found to exhibit different functions in vitro and in vivo such as antihypertensive, hepatoprotective, anti-obesity, antimicrobial, antioxidative, mineral-binding and accelerating alcohol metabolism. To date, 22 sequences of bioactive corn peptides have already been identified. There is an increasing commercial interest in the production of corn peptides with the purpose of using them as active ingredients, which may find use in the treatment of liver injury, hypertension, dental carries, oxidative stress, mineral malabsorption and obesity. These bioactive peptides may be used in formulation of functional foods, nutraceuticals, and natural drugs because of their health benefit effects.

Effects of natural peptides from food proteins on angiotensin converting enzyme activity and hypertension

Cardiovascular diseases are the leading cause of death. The underlying pathophysiology is largely contributed by an overactivation of the renin-angiotensin-aldosterone-system (RAAS). Herein, angiotensin II (AngII) is a key mediator not only in blood pressure control and vascular tone regulation, but also involved in inflammation, endothelial dysfunction, atherosclerosis, hypertension and congestive heart failure. Since more than three decades suppression of AngII generation by inhibition of the angiotensin-converting enzyme (ACE) or blockade of the AngII-receptor has shown clinical benefit by reducing hypertension, atherosclerosis and other inflammation-associated cardiovascular diseases. Besides pharmaceutical ACE-inhibitors some natural peptides derived from food proteins reduce in vitro ACE activity. Several animal studies and a few human clinical trials have shown antihypertensive effects of such peptides, which might be attractive as food additives to prevent age-related RAAS activation. However, their inhibitory potency on in vitro ACE activity does not always correlate with an antihypertensive impact. While some peptides with high inhibitory activity on ACE-activity in vitro show no antihypertensive effect in vivo, other peptides with only a moderate ACE inhibitory activity in vitro cause such effects. The explanation for this conflicting phenomenon between inhibitory activity and antihypertensive effect remains unclear to date. This review shall critically address the effects of natural peptides derived from different food proteins on the cardiovascular system and the possible underlying mechanisms. A central aspect will be to point to conceptual gaps in the current understanding of the action of these peptides with respect to in vivo blood pressure lowering effects.

Mung-bean Protein Hydrolysates Obtained with Alcalase Exhibit Angiotensin I-converting Enzyme Inhibitory Activity

Mung-bean protein isolates were hydrolysed by two proteases alcalase and neutrase commercially available for food industry use, and the angiotensin I-converting enzyme (ACE) inhibitory activities of the enzymatic hydrolysates were measured at different hydrolysis times. The non-hydrolysed protein showed no inhibitory activity. Hydrolysates generated with neutrase displayed very low ACE inhibitory activity, while those obtained with alcalase exhibited high inhibitory activity. The highest ACE inhibitory activity with the IC50 value of 0.64 mg protein/mL was found in the hydrolysate obtained with alcalase at 2h of hydrolysis time. These results indicated that mung-bean protein is a good protein source of ACE inhibitory peptides when hydrolysed with the protease alcalase. The mung-bean protein hydrolysates prepared with alcalase might be utilised for physiologically functional foods with antihypertensive activity.

A pursuit of the functional nutritional and bioactive properties of canola proteins and peptides

This review focuses on updated information about canola proteins and peptides, their functional, nutritional, and bioactive properties, safety aspects, and potential application in foods. Attention is paid to gelation, emulsion, thermal, and water holding capacities of crude and pure proteins and peptides isolated from canola meal. Various factors affecting these properties are discussed. This paper provides an overview of use of canola meal as a protein source in animal diets and their digestibility in vivo. Their effects on a range of health outcomes including ACE inhibition, hypocholesterolemic effects, cancer prevention, anti-viral and anti-diabetic properties are reviewed on the basis of the available in vitro and in vivo animal and human data. The review also focuses on the safety aspects and selected food applications of canola proteins and peptides.

Development of a reversed-phase high-performance liquid chromatography analytical methodology for the determination of antihypertensive peptides in maize crops

The aim of this work was to estimate the content of three highly antihypertensive peptides (LQP, LSP, and LRP) in different maize crops. For that purpose, a method consisting of the extraction of the protein containing these peptides (α-zeins), releasing of peptides by thermolysin digestion, and separation and detection of peptides was designed. The rapid and efficient ultrasound assisted extraction of α-zeins proteins from whole maize kernels was achieved using 70% of ethanol followed by precipitation with acetone. A 10 mM Tris-HCl (pH 8.0) buffer containing 8M urea enabled to dissolve the precipitated α-zeins. This buffer was diluted to reach a 6 M urea concentration before digestion to keep active the enzyme. Other digestion parameters that were optimized were: enzyme to substrate ratio (5:100 was selected), digestion temperature (50°C) and digestion time (6 h). The RP-HPLC separation in a fused-core column was also optimized allowing the separation of the three peptides extracted from maize kernels in 6 min. The presence of the three antihypertensive peptides in the digested extract was confirmed using HPLC-Q-TOF-MS analysis and by comparison with peptide standards. Clear differences were observed in the content of the three antihypertensive peptides and, thus, in the antihypertensive activity of the analyzed crops. The content of LRP peptide was very low regardless of the maize variety while the content of LQP and LSP significantly varied among studied maize lines.

Production of Fermentative Hydrolysate with Antioxidative Activity of Extruded Corn Gluten Meal by Bacillus natto

Fermentative hydrolysate of extruded corn gluten with higher solubility and antioxidative property by Bacillus natto was prepared. Extrusion of corn gluten was applied as pretreatment before fermentation. The best fermentative hydrolysis results can be obtained by fermenting at 34°C for cultivation time of 32 h, and flask rotation speed and initial pH of culture media were 200 r/min and 6.5-7.0 respectively. Soluble protein content and antioxidative activity of the fermentative hydrolysate reached 24.95 mg/ml and 259.21 U/ml respectively under the optimized culture condition. The molecular weight of the peptides in the optimal hydrolysate distributed mainly over 860-5300 Da determined by gel filtration chromatography. The hydrolysates displayed good solubility and antioxidative activity.

Effects of corn gluten hydrolyzates, branched chain amino acids, and leucine on body weight reduction in obese rats induced by a high fat diet

In this study, we compared corn gluten hydrolyzates, BCAAs, and leucine for their effects on body weight reduction in high fat-induced obese rats in order to determine the major active components in the corn gluten hydrolyzates. After obesity was induced for 13 weeks with high fat diet, the overweight-induced SD rats (n = 64) were stratified according to body weight, randomly blocked into eight treatments, and raised for 8 weeks. Four groups were changed to a normal diet and the other groups remained on the high fat diet. Each of the groups within both diets was fed either casein, corn gluten hydrolyzates, leucine, or branched chain amino acids, respectively. Daily food intake, body weight gain, and food efficiency ratio were significantly lower in the corn gluten hydrolyzate groups compared to the other groups, regardless of the high fat diet or normal fat diet. The rats fed the corn gluten hydrolyzates diet had the lowest perirenal fat pad weights whereas muscle weight was significantly increased in the corn gluten hydrolyzates groups. Plasma triglyceride, hepatic total lipid, and total cholesterol contents were significantly reduced in the corn gluten hydrolyzates groups. Other lipid profile measurements were not significantly changed. Plasma triglyceride and hepatic total lipid were also significantly reduced in the BCAA and leucine groups. Leptin levels were significantly lower and adiponectin was significantly higher in the corn gluten hydrolyzates groups. Fasting blood glucose, insulin, C-peptide, and HOMA-IR levels were also significantly reduced in the corn gluten hydrozylates groups, regardless of fat level.

Effect of corn gluten and its hydrolysate consumptions on weight reduction in rats fed a high-fat diet

This study examined the effects of corn gluten (CG) and its hydrolysate consumptions on weight reduction in rats fed a high-fat diet. Eight-month-old male Sprague-Dawley rats (n=40) were fed a high-fat diet (40% calorie as fat) for 4 weeks. They were then randomly divided into four groups and fed the isocaloric diets with different protein sources for 8 weeks. The protein sources were casein (control group), intact CG (CG group), CG hydrolysate A (CGHA group, 30% of protein as peptides and 70% as free amino acids) and CG hydrolysate P (CGHP group, 93% of protein as peptides and 7% as free amino acids). Body weight gain, adipose tissue weights, nitrogen balance, absorptions of energy, protein and fat, lipid profiles in plasma, liver and feces and hepatic activities of carnitine palmitoyl transferase (CPT), fatty acid synthase (FAS), malic enzyme (ME) and glucose-6-phosphate dehydrogenase (G6PDH) were assessed. The CGHA diet had the highest amount of BCAAs, especially leucine, and most of them existed as free amino acid forms. The CGHA group showed significant weight reduction and negative nitrogen balance. Protein absorption and apparent protein digestibility in the CGHA group were significantly lower than those in other groups. Adipose tissue weights were the lowest in the CGHA group. Activity of CPT tended to be higher in the CGHA group than in other groups and those of FAS, ME and G6PDH were significantly lower in the CGHA group than in other groups. In conclusion, the CGHA diet which had relatively high amounts of free amino acids and BCAAs, especially leucine, had a weight reduction effect by lowering adipose tissue weight and the activities of FAS, ME and G6PDH in experimental animals, but it seemed to be a negative result induced by lowering protein absorption, increasing urinary nitrogen excretion and protein catabolism.

Physicochemical and bitterness properties of enzymatic pea protein hydrolysates

The effects of different proteolytic treatments on the physiochemical and bitterness properties of pea protein hydrolysates were investigated. A commercial pea protein isolate was digested using each of 5 different proteases to produce protein hydrolysates with varying properties. After 4 h of enzyme digestion, samples were clarified by centrifugation followed by desalting of the supernatant with a 1000 Da membrane; the retentates were then freeze-dried. Alcalase and Flavourzymetrade mark produced protein hydrolysates with significantly higher (P < 0.05) degree of hydrolysis when compared to the other proteases. Flavourzyme, papain, and alcalase produced hydrolysates that contained the highest levels of aromatic amino acids, while trypsin hydrolysate had the highest levels of lysine and arginine. Papain hydrolysate contained high molecular weight peptides (10 to 178 kDa) while hydrolysates from the other 4 proteases contained predominantly low molecular weight peptides ( Collapse

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MESH Headings

• Angiotensin-Converting Enzyme Inhibitors/metabolism
• Biphenyl Compounds
• Endopeptidases/metabolism
• Food Handling/methods
• Food, Organic
• Free Radical Scavengers/metabolism
• Humans
• Hydrazines
• Molecular Weight
• Nutritive Value
• Papain/metabolism
• Pisum sativum/chemistry
• Peptide Hydrolases/metabolism
• Picrates
• Protein Hydrolysates/analysis
• Subtilisins/metabolism
• Taste
• Trypsin/metabolism

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Affiliation(s)

L M Humiski Dept. of Human Nutritional Sciences, Univ. of Manitoba, Winnipeg, Manitoba, R3T 2N2, Canada
R E Aluko

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Production of hydrolysate with antioxidative activity by enzymatic hydrolysis of extruded corn gluten

Hydrolysate of extruded corn gluten with higher solubility and antioxidative property was prepared. Extrusion and starch removal of corn gluten were applied as pretreatment before enzymatic hydrolysis by Alcalase. The amylase hydrolysis of starch at 70 degrees C for 3 h resulted in the removal of the starch from the extruded corn gluten. The best hydrolysis results can be obtained by conducting the hydrolysis at 60 degrees C with water addition 20 g/g protein, enzyme addition 0.048 Ansen units/g protein, pH 8.5, and 120 min. Degree of hydrolysis of extruded and nonextruded corn gluten reached 39.54 and 31.16%, respectively, under the optimal condition. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of the optimal hydrolysate revealed that proteolysis of extruded corn gluten was more extensive than proteolysis of its counterpart which was not subjected to extrusion. The molecular weight of the peptides in the optimal hydrolysate was mainly over 3,710-660 Da as determined by gel filtration chromatography. The hydrolysates displayed good solubility and antioxidative activity. The separation profile of the hydrolysate on an ion exchange chromatography of Q-Sepharose Fast Flow showed that many kinds of peptides had antioxidative effect. A new peptide with antioxidative activity was purified, and its amino acid sequence was Phe-Pro-Leu-Glu-Met-Met-Pro-Phe, which was identified by Q-TOF2 mass spectrometry.

Direct spectrophotometric measurement of angiotensin I-converting enzyme inhibitory activity for screening bioactive peptides

A direct, extraction-free spectrophotometric assay was developed for determination of angiotensin I-converting enzyme activity (ACE) in the presence of ACE inhibitors using hippuryl-l-histidyl-l-leucine (HHL) as the ACE-specific substrate. This method relies on previously published spectrophotometric determination of hippuric acid (HA) content in the urine, the method of which was based on the specific colorimetric reaction of HA with benzene sulfonyl chloride (BSC) in the presence of quinoline. The proposed ACE inhibition assay was applied to the measurement of the ACE inhibitory activity of Captopril. IC(50) value of Captopril corresponded well with literature data. Furthermore, Alcalase hydrolysates of mung bean and rice protein isolates were assessed for ACE inhibitory activity by this method. These two hydrolysates showed high ACE inhibitory activity. This method proposed here was shown to be direct, sensitive, accurate, reproducible, and less expensive without separation of HA from ACE reaction mixture, and can be used for the screening of ACE inhibitory peptides derived from food proteins.