Characterization of a purified α-amylase inhibitor from white kidney beans (Phaseolus vulgaris)

Purification and Characterization of Proteinaceous Thermostable α-Amylase Inhibitor from Sardinian Common Bean Nieddone Cultivar (Phaseolus vulgaris L.)

The increasing need for new treatments for obesity and diabetes has led to the development of new drugs and food supplements that could reduce carbohydrate absorption. Many starch blockers, based on common bean proteinaceous inhibitors against α-amylase (α-AI), are already present on the market. The extraction and purification of α-amylase inhibitor from a promising common bean cultivar from Sardinia (Nieddone) is described, highlighting the unique value of the Nieddone cultivar, particularly for its inhibitory activity on digestive enzymes and its complete lack of a hemagglutination effect on human red blood cells. The purification of α-AI involved two chromatographic steps (IEC and SEC) and was essential for revealing certain properties of the inhibitor. The purified inhibitor has a tetrameric structure (α2β2) and a molecular weight of approximately 42 kDa, as determined by SEC and SDS-PAGE, confirming it as a lectin-like inhibitor. The identification of the α-AI sequence was obtained by bottom-up high-resolution mass spectrometry, which allowed us to identify a unique peptide from the α chain and six unique peptides from the β chains. α-AI exhibited an optimum temperature of around 40 °C and two pH optima at 5 and 6.5, respectively. Its remarkable stability at high temperatures was measured (approximately 25% of activity retained even after 5 h at 100 °C), whereas the raw extract lost its activity entirely after just 10 min at 90 °C. Thus, the purification process significantly enhances the thermal stability of α-AI. The demonstrated effectiveness of the purified α-AI against the α-amylase enzyme in pigs, humans and insects underscores the protein's potential for treating obesity and diabetes, as well as for managing insect pests.

Common bean (Phaseolus vulgaris L.) α-amylase inhibitors as safe nutraceutical strategy against diabetes and obesity: An update review

Overweight and obesity are constantly increasing, not only in Western countries but also in low‐middle‐income ones. The decrease of both the intake of carbohydrates and their assimilation are among the main dietary strategies to counter these conditions. α‐Amylase, a key enzyme involved in the digestion of carbohydrates, is the target enzyme to reduce the absorption rate of carbohydrates. α‐Amylase inhibitors (α‐AIs) can be found in plants. The common bean, Phaseolus vulgaris is of particular interest due to the presence of protein‐based α‐AIs which, through a protein–protein interaction, reduce the activity of this enzyme. Here we describe the nature of the various types of common bean seed extracts, the type of protein inhibitors they contain, reviewing the recent Literature about their molecular structure and mechanism of action. We also explore the existing evidence (clinical trials conducted on both animals and humans) supporting the potential benefits of this protein inhibitors from P. vulgaris, also highlighting the urgent need of further studies to confirm the clinical efficacy of the commercial products. This work could contribute to summarize the knowledge and application of P. vulgaris extract as a nutraceutical strategy for controlling unwanted weight gains, also highlighting the current limitations.

Dietary Intervention With α-Amylase Inhibitor in White Kidney Beans Added Yogurt Modulated Gut Microbiota to Adjust Blood Glucose in Mice

White kidney beans contain α-amylase inhibitors that can be used in diet for weight reduction. In this study, we investigated the potential of white kidney bean (phaseolus vulgaris L.) extract enriched in α-amylase inhibitor as a food additive in yogurt to regulate blood glucose in hyperglycemic animals. Five groups of C57BL/6J mice were fed for 8 weeks with standard chow diets, high-fat diets (HFD), or high-fat diets with supplement of α-amylase inhibitor in white kidney beans (P. vulgaris extract, PVE), yogurt (Y), and PVE added yogurt (YPVE), respectively. The HFD weakened glucose tolerance and caused insulin resistance in mice, and changed the characteristics of intestinal flora. The intervention of Y, PVE, and YPVE decreased blood glucose, insulin, hyperlipidemia, and inflammatory cytokine levels in mice fed with HFD. Moreover, the YPVE could regulate the components of host intestinal microbiota toward a healthy pattern, significantly increased the metabolic-related flora Corynebacterium, Granulicatella, and Streptococcus, while it decreased Paraprevotella and Allobaculum. Thus, YPVE markedly increased functions of "Amino Acid Metabolism," "Energy Metabolism," "Nucleotide Metabolism," and declined functions of "Glycan Biosynthesis and Metabolism." Consequently, YPVE could be developed as a new functional food because of its beneficial prebiotic properties in the metabolic syndrome.

Regular intake of white kidney beans extract (Phaseolus vulgaris L.) induces weight loss compared to placebo in obese human subjects

Scope

Phaseolus vulgaris L. is rich in alpha-amylase inhibitor and has been used for reducing glycemia and calories absorption through preventing or delaying the digestion of complex carbohydrate. A randomized, double-blinded, placebo-controlled study was conducted on obese volunteers to evaluate the degree of significate weight loss by regular intake Phaseolus vulgaris cultivated from Southwestern region of China.

Method

The volunteers were divided into two groups, homogeneous for age, gender, and body weight. Phaseolus vulgaris extract or placebo was given 2,400 mg per day before each daily meal for 35 consecutive days. Each subject's body weight, fat mass, body mass index, blood biochemical parameters, skinfold fat thickness, and waist/hip circumferences were monitored and analyzed.

Result and conclusion

As a result, the average amount of weight lost by the Phaseolus vulgaris extract group was 2.24 kg (average of 0.448 kg per week), compared with a 0.29 kg weight loss (average of 0.058 kg per week) in placebo group after 35 days. The differences between groups were significant (p < .01). The body mass index decreased by an average of 0.79, and the body fat decreased by 1.53% on average compared to baseline (p < .05). The thickness of subcutaneous fat was significantly reduced at the four measurement points, and the decrease of waist circumference and hip circumference was significant as well. No adverse or side effects were observed during the trial period. The results indicate that Phaseolus vulgaris extract can significantly induce weight loss in a short time period.

Subchronic Study of a White Kidney Bean (Phaseolus vulgaris) Extract with α-Amylase Inhibitory Activity

Common bean extract as a dietary supplement has received increased attention globally owing to its α-amylase inhibitory activity. The objective of this study was to evaluate the toxicity of a white kidney bean (Phaseolus vulgaris) extract by a repeated-dose 90-day subchronic oral toxicity study in Sprague-Dawley rats. In the subchronic toxicity study, 80 rats were orally administrated with white kidney bean extract at doses of 4, 2, and 1 g/kg body weight daily for 90 days. The results showed that the white kidney bean extract at doses up to 4 g/kg/day did not induce significant changes in body weight, organ weight, food consumption, hematology, serum biochemistry, and histopathology in rats, as compared to the control. The no-observed-adverse-effect level (NOAEL) of white kidney bean extract was determined to be >4 g/kg/day for both male and female rats, under the experimental conditions of this study.

Suppressive Effect of the α-Amylase Inhibitor Albumin from Buckwheat (Fagopyrum esculentum Moench) on Postprandial Hyperglycaemia

Inhibiting starch hydrolysis into sugar could reduce postprandial blood glucose elevation and contribute to diabetes prevention. Here, both buckwheat and wheat albumin that inhibited mammalian α-amylase in vitro suppressed blood glucose level elevation after starch loading in vivo, but it had no effect after glucose loading. In contrast to the non-competitive inhibition of wheat α-amylase inhibitor, buckwheat albumin acted in a competitive manner. Although buckwheat α-amylase inhibitor was readily hydrolysed by digestive enzymes, the hydrolysate retained inhibitory activity. Together with its thermal stability, this suggests its potential use in functional foods that prevent diabetes.

A bifunctional α-amylase/trypsin inhibitor from pigeonpea seeds: Purification, biochemical characterization and its bio-efficacy against Helicoverpa armigera

This paper evaluates α-amylase inhibitor (α-AI) mediated defense of pigeonpea against Helicoverpa armigera. A bifunctional α-amylase/trypsin inhibitor was purified from the seeds of pigeonpea by native liquid phase isoelectric focusing (N-LP-IEF), affinity chromatography and preparative electrophoresis. Its in-vivo and in-vitro interaction with midgut amylases of H. armigera was studied along with growth inhibitory activity. One and two dimensional (2D) zymographic analyses revealed that the purified inhibitor is dimeric glycoprotein (60.2kDa and 56kDa) exist in a multi-isomeric form with five pI variants (pI 5.5 to 6.3). It was found to be heat labile with complete inactivation up to 80°C and stable over a wide range of pH (4-11). The slow binding and competitive type of α-amylase inhibition was observed with 0.08μM of dissociation constant (Ki) for the enzyme-inhibitor complex (EI). The internal protein sequence of two subunits obtained by mass spectrometry matched with cereal-type α-AI, a conserved domain from AAI_LTSS superfamily and sialyltransferase-like protein respectively. In-vivo studies indicated up-regulation of total midgut α-amylase activity with negative effect on growth rate of H. armigera suggesting its suitability for pest control.

Susceptibility of sweet potato (Ipomoea batatas) peel proteins to digestive enzymes

Sweet potato proteins have been shown to possess antioxidant and antidiabetic properties in vivo. The ability of a protein to exhibit systemic effects is somewhat unusual as proteins are typically susceptible to digestive enzymes. This study was undertaken to better understand how digestive enzymes affect sweet potato proteins. Two fractions of industrially processed sweet potato peel, containing 6.8% and 8.5% protein and 80.5% and 83.3% carbohydrate, were used as a source of protein. Sweet potato proteins were incubated with pepsin, trypsin, and chymotrypsin and protein breakdown was visualized with SDS-PAGE. After pepsin digestion, samples were assayed for amylase inhibitory activity. Sporamin, the major storage protein in sweet potatoes, which functions as a trypsin inhibitor as well, exhibited resistance to pepsin, trypsin, and chymotrypsin. Sporamin from blanched peel of orange sweet potatoes was less resistant to pepsin digestion than sporamin from outer peel and from extract of the white-skinned Caiapo sweet potato. Trypsin inhibitory activity remained after simulated gastric digestion, with the Caiapo potato protein and peel samples exhibiting higher inhibitory activity compared to the blanched peel sample. Amylase and chymotrypsin inhibitory activity was not present in any of the samples after digestion.

Appetite control and gastrointestinal hormonal behavior (CCK, GLP-1, PYY 1-36) following low doses of a whey protein-rich nutraceutic

Whey proteins represent the most satiating nutrients. In particular, their effects are due to enterohormonal changes (CCK, GLP-1 and PYY 1–36) observed after their exclusive ingestion. Glucomannan has important satiety property due to volume increase following gelification. The aim of the study is the evaluation of subjective rate of hunger and enterohormone concentrations (CCK, GLP-1, PYY 1–36) following oral loading of a mixture containing WP (8 g) or casein (8 g) plus glucomannan (1 g) (Colordiet^®, Inpha DUEMILA Srl Lecco, Italy). The study was conducted as a double-blind crossover with five healthy volunteers (BMI 22–26 kg/m² aging 18–65 years) in acute and a wash-out period of 1 week between the first and the second evaluation. From the analysis of the data, we observe that the load with WP induces a significant decrease in the desire to eat after 90 min (P < 0.0446) when compared with casein. As far as plasma hormones are concerned, there was a significant increase only in GLP-1 at 90 min after WP (P < 0.00166) and 180 min after casein (T0 vs. T180 P = 0.000129). There is a significant correlation between the increase in GLP-1 and decrease of desire to eat (R = −0.93). There is a tendency to the increasing of CCK after 90 min, which is not significant (P = 0.091). These results could be due to (a) the low number of cases or (b) the low dose of protein used. The present study suggests that a mixture of WP plus glucomannan exerts a decrease in the desire to eat which is correlated to enterohormonal modification (GLP-1 increase) despite the low content of protein (8 g) and the presence of glucomannan, which could reduce the fast absorption of WP in relation to the net forming during the gelification of the gastric environment.

Wheat drought-responsive grain proteome analysis by linear and nonlinear 2-DE and MALDI-TOF mass spectrometry

A comparative proteomic analysis of drought-responsive proteins during grain development of two wheat varieties Kauz (strong resistance to drought stress) and Janz (sensitive to drought stress) was performed by using linear and nonlinear 2-DE and MALDI-TOF mass spectrometry technologies. Results revealed that the nonlinear 2-DE had much higher resolution than the linear 2-DE. A total of 153 differentially expressed protein spots were detected by both 2-DE maps, of which 122 protein spots were identified by MALDI-TOF and MALDI-TOF/TOF mass spectrometry. The identified differential proteins were mainly involved in carbohydrate metabolism (26%), detoxification and defense (23%), and storage proteins (17%). Some key proteins demonstrated significantly different expression patterns between the two varieties. In particular, catalase isozyme 1, WD40 repeat protein, LEA and alpha-amylase inhibitors displayed an upregulated expression pattern in Kauz, whereas they were downregulated or unchanged in Janz. Small and large subunit ADP glucose pyrophosphorylase, ascorbate peroxidase and G beta-like protein were all downregulated under drought stress in Janz, but had no expression changes in Kauz. Sucrose synthase and triticin precursor showed an upregulated expression pattern under water deficits in both varieties, but their upregulation levels were much higher in Kauz than in Janz. These differentially expressed proteins could be related to the biochemical pathways for stronger drought resistance of Kauz.

The nutraceutical role of thePhaseolus vulgarisα-amylase inhibitor

The present review assesses the potential of thePhaseolus vulgarisα-amylase inhibitor isoform 1 (α-AI1) starch blockers as a widely used remedy against obesity and diabetes. Consumption of the α-amylase inhibitor causes marginal intraluminal α-amylase activity facilitated by the inhibitor's appropriate structural, physico-chemical and functional properties. As a result there is decreased postprandial plasma hyperglycaemia and insulin levels, increased resistance of starch to digestion and increased activity of colorectal bacteria. The efficacy and safety of the amylase inhibitor extracts, however, depend on the processing and extraction techniques used. The extracts are potential ingredients in foods for increased carbohydrate tolerance in diabetics, decreased energy intake for reducing obesity and for increased resistant starch. Research developments in the distribution and biosynthesis of the α-amylase inhibitor, relevant physico-chemical properties, the molecular starch-blocking mechanism, anti-obesity and anti-diabetes effects, safety of extracts and the need for research into their potential anti-colorectal cancer effect are discussed.

Nutritional significance of lectins and enzyme inhibitors from legumes

Legumes have natural components, such as lectins, amylase, and trypsin inhibitors, that may adversely affect their nutritional properties. Much information has already been obtained on their antinutritional significance and how to inactivate them by proper processing. Chronic ingestion of residual levels is unlikely to pose risks to human health. On the other hand, the ability of these molecules to inhibit some enzymes such as trypsin, chymotrypsin, disaccharidases, and alpha-amylases, to selectively bind to glycoconjugates, and to enter the circulatory system may be a useful tool in nutrition and pharmacology. Trypsin inhibitors have also been studied as cancer risk reducing factors. These components seem to act as plant defense substances. However, increased contents may represent an impairment of the nutritional quality of legumes because these glycoproteins and the sulfur-rich protease inhibitors have been shown to be poorly digested and to participate in chemical reactions during processing reducing protein digestibility, a still unsolved question.

Applications of mass spectrometry to food proteins and peptides

The application of mass spectrometry (MS) to large biomolecules has been revolutionized in the past decade with the development of electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) techniques. ESI and MALDI permit solvent evaporation and sublimation of large biomolecules into the gaseous phase, respectively. The coupling of ESI or MALDI to an appropriate mass spectrometer has allowed the determination of accurate molecular mass and the detection of chemical modification at high sensitivity (picomole to femtomole). The interface of mass spectrometry hardware with computers and new extended mass spectrometric methods has resulted in the use of MS for protein sequencing, post-translational modifications, protein conformations (native, denatured, folding intermediates), protein folding/unfolding, and protein-protein or protein-ligand interactions. In this review, applications of MS, particularly ESI-MS and MALDI time-of-flight MS, to food proteins and peptides are described.