7S Fractions Research Articles

Soymorphins, Novel μ Opioid Peptides Derived from Soy β-Conglycinin β-Subunit, Have Anxiolytic Activities

Based on the amino acid sequence YPFV found in the soy beta-conglycinin beta-subunit, which is common to an opioid peptide human beta-casomorphin-4, peptides YPFVV, YPFVVN, and YPFVVNA were synthesized according to their primary structure. On guinea pig ileum (GPI) assay, they showed opioid activity (IC50 = 6.0, 9.2 and 13 microM respectively) more potent than human beta-casomorphins, and were named soymorphins-5, -6, and -7, respectively. Their opioid activities on mouse vas deferens (MVD) assay were less potent than on GPI assay, suggesting that they are selective for the mu opioid receptor. Human beta-casomorphin-4 and soymorphin-5 were released from the soy 7S fraction (beta-conglycinin) by the action of gastrointestinal proteases. Soymorphins-5, -6, and -7 had anxiolytic activities after oral administration at doses of 10-30 mg/kg in the elevated plus-maze test in mice.

Assessing Glycinin (11S) and β‐Conglycinin (7S) Fractions of Soybean Storage Protein by Near‐Infrared Spectroscopy

AbstractSoybean breeding programs underway today are addressing the goal of improving the protein profile to benefit the human diet as well as that of livestock. Glycinin, a globulin storage protein of the meal and designated as the 11S size fraction by ultracentrifugation, is desirable because of its relative abundance of sulfur‐containing amino acids, such as methionine and cysteine. The current study examined the feasibility of near‐infrared (NIR) measurement of glycinin and the other prevalent protein fraction, β‐conglycinin (7S size fraction), as well as the electrophoretically separable sub fractions that comprise these two components. From a population of 101 F6‐derived recombinant inbred lines in a field replicated trial, single whole soybeans were scanned in transmittance (800–1,798 nm, 24 beans/sample × 197 samples total). Additional scanning of the ground meal was performed in reflectance (1,100–2,498 nm). Partial least squares (PLS) calibrations were developed, using the 24‐bean average log(1/T) spectrum for each sample, as well as the average spectrum from duplicate packs of log(1/R) spectra of the meal. The results indicate that NIR prediction of 11S and 7S, as well as the sub fractions thereof, is at best limited to screening purposes in soybean breeding programs for probable reasons of an inherent lack of spectral specificity of the protein fractions and a non‐constant proportion of soluble‐to‐total protein.

Replacement of dietary soy protein isolate with concentrates of soy 7S or 11S globulin has minimal or no effects on plasma lipoprotein profiles and biomarkers of coronary risk in monkeys

Effects of soy peptide fractions on risk factors for coronary heart disease are unknown. We compared the effects of a soy protein isolate, a soy 7S fraction concentrate and a soy 11S fraction concentrate on total plasma cholesterol, HDL cholesterol, LDL+VLDL cholesterol and triacylglycerol in adult male cynomolgus monkeys. Effects on biomarkers of coronary risk [soluble E-selectin, vascular cell-adhesion molecule-1 (VCAM-1), monocyte chemoattractant protein-1 (MCP-1), transforming growth factor β-1 (TGF-β-1) and plasminogen activator inhibitor-1 (PAI-1)] were also determined. Relative to a soy- and isoflavone-free diet (casein and lactalbumin as the source of protein), soy protein isolate had the predicted favorable effects on plasma lipoproteins, i.e., reductions in total and VLDL+LDL cholesterol (8 and 14%, respectively) (P's<0.05) and a 41% increase in HDL (P<0.05). Effects of 7S and 11S on these variables were less favorable. In fact, there was a 7% increase in total plasma cholesterol concentration (P<0.05) in monkeys fed 7S that was accounted for primarily by an increase in VLDL+LDL cholesterol. There was no effect of any protein source on cardiovascular biomarkers. Replacement of dietary soy protein isolate with concentrated 7S or 11S does not result in improvement of plasma lipoprotein profiles or cardiovascular biomarkers in monkeys.

The Proteasome Regulates HIV-1 Transcription by Both Proteolytic and Nonproteolytic Mechanisms

Although the proteasome facilitates transcription from several yeast promoters, it is unclear if its role is proteolytic or which subunits are involved. We show that the proteasome regulates the HIV-1 promoter in both proteolytic and nonproteolytic modes. In the absence of transcription factor, Tat, proteasome was associated with promoter and coding regions, and its proteolytic activity regulated the level of basal transcription emanating from the promoter. Tat switched the proteasome to a nonproteolytic mode by recruiting a proteasome-associated protein, PAAF1, which favors proteasome dissociation into 19S and 20S particles. Gel filtration chromatography showed that expression of both Tat and PAAF1 enhanced the abundance of a 19S-like complex in nuclear extracts. 19S, but not 20S, subunits were strongly recruited to the promoter in the presence of Tat and PAAF1 and coactivated Tat-dependent transcription. 19S components facilitated transcriptional elongation and may be involved in clearance of paused transcriptional elongation complexes from the promoter.

In vitro glycation and antigenicity of soy proteins

Abstract Soy protein isolate (SPI) was glycated with fructose or fructooligosaccharides (FOS) through the Maillard reaction in powder and liquid systems. A reduction in primary free amino groups of SPI up to 85% and 96% was observed in the powder and liquid system, respectively. Following heating at 95 °C for 1 h under liquid conditions, the electrophoretic behavior of allergenic 7S (β-conglycinin) and 11S (glycinin) fractions of SPI was modified when glycated with FOS (molar ratio primary amino groups to FOS of 1:74) as shown by SDS-PAGE analysis. The antigenicity of this glycated protein was also largely reduced (up to ∼90%) compared with that of the unglycated form. Glycation reactions with fructose in a powder and liquid system also reduced the antigenicity of the glycated proteins.

Optimization of extraction and isolation for 11S and 7S globulins of soybean seed storage protein

A new method was developed for extraction and isolation of 7S and 11S fractions from soybean seed, based on methods of Nagano et al., Thanh and Shibasaki [Nagano, T., Hirotsuka, M., & Mori, H. (1992). Dynamic viscoelastic study on the gelation of 7S globulin from soybeans. Journal of Agricultural and food chemistry 40, 941–944 and Thanh, V. H., & Shibasaki, K. (1976). Major proteins of soybean seeds. A straightforward fraction and their characterization. Journal of Agricultural and Food Chemistry 24, 1117–1121]. Optimization of the extraction and isolation of 11S and 7S globulins from soybean seed was investigated under various conditions by the Kjeldahl method and SDS-PAGE. The optimal conditions were as follows: 0.03–0.06 M Tris–HCl buffer (pH 8.5) containing 0.01 M sodium bisulfite as extract solution, extraction twice at 45 °C for 1 h, and with a 1:15 ratio ( w/v) of flour:Tris–HCl. The 11S fraction was precipitated at pH 6.4, and the supernatant, after centrifugation, was adjusted to pH 5.5 to remove the insoluble intermediate fraction by further centrifugation. The supernatant obtained was then adjusted to pH 4.8 to afford the 7S fraction as a precipitate by centrifugation. With the improvements, the protein contents and purities of the isolated 11S and 7S fractions were significantly increased. The contents of all subunits of the isolated 11S and 7S fraction were markedly higher than those by Thanh and Shibasaki method, while the contents of α, β and B 3 were also significantly higher than those by Nagano et al. method.

Interactions between Whey Protein Isolate and Soy Protein Fractions at Oil–Water Interfaces: Effects of Heat and Concentration of Protein in the Aqueous Phase

ABSTRACT: The 2 main storage proteins of soy—glycinin (11S) and β‐conglycinin (7S)—exhibit unique behaviors during processing, such as gelling, emulsifying, or foaming. The objective of this work was to observe the interactions between soy protein isolates enriched in 7S or 11S and whey protein isolate (WPI) in oil–water emulsion systems. Soy oil emulsion droplets were stabilized by either soy proteins (7S or 11S rich fractions) or whey proteins, and then whey proteins or soy proteins were added to the aqueous phase. Although the emulsifying behavior of these proteins has been studied separately, the effect of the presence of mixed protein systems at interfaces on the bulk properties of the emulsions has yet to be characterized. The particle size distribution and viscosity of the emulsions were measured before and after heating at 80 and 90 °C for 10 min. In addition, SDS‐PAGE electrophoresis was carried out to determine if protein adsorption or exchanges at the interface occurred after heating. When WPI was added to soy protein emulsions, gelling occurred with heat treatment at WPI concentrations &gt;2.5%. In addition, whey proteins were found adsorbed at the oil–water interface together with 7S or 11S proteins. When 7S or 11S fractions were added to WPI‐stabilized emulsions, no gelation occurred at concentrations up to 2.5% soy protein. In this case also, 7S or 11S formed complexes at the interface with whey proteins during heating.

Detection of 7S and 11S soy protein fractions by monoclonal antibody-based immunoassays in food

A panel of four monoclonal antibodies (MAbs) recognizing antigenic determinants on soy protein was produced and partially characterized. The protein fractions 7S and 11S were extracted and purified from the soy protein isolate and defatted flour of soy, respectively. To obtain hybridomas, popliteal lymph nodes of BALB/c immunized mice (10,0 µg protein/footpad) were excised and fused to SP2-0 myeloma cells. The hybridomas were screened by enzyme-linked immunosorbent assay (ELISA) using peroxidase-labelled rat anti-mouse IgG MAb and cloned under limiting dilution conditions. The specificity of these antibodies was evaluated by Western blotting. Three antibodies produced by stable clones (1H4, 2A8 and 1F9) recognized the subunits α, α′ and β of the 7S soy protein fraction and one monoclonal antibody (3F2) recognized the basic subunit of the 11S fraction. ELISA assays with the MAbs anti-7S (IgG2b) and 11S (IgG1) fractions were able to detect the presence of these fractions in soy-containing commercial products as yogurt, milk and juice. The present study showed that these MAbs specifically detect the subunits of the 7S fraction and the basic subunits of the 11S fraction of soy protein and may be used in immunoassays to detect these protein fractions in soy-based products.

Quantitative trait loci for β‐conglycinin (7S) and glycinin (11S) fractions of soybean storage protein

AbstractGlycinin (11S) and β‐conglycinin (7S) are important seed storage proteins in soybean [Glycine max (L.) Merr.]. A major limitation of soybean seed storage proteins is their low levels of the sulfur‐containing amino acids, methionine and cysteine, which are important nutritional components of protein mea. Glycinin contains significantly more S‐containing amino acids than does β‐conglycinin. Thus, detection of quantitative trait loci (QTL) that govern 11S may provide marker‐assisted selection (MAS) opportunities to improve soybean total S‐containing amino acids. The objective of this study was to detect and map QTL governing 7S and 11S fractions of soybean seed storage proteins. To achieve this objective, 101 F6‐derived recombinant inbred lines (RIL) developed from a cross of N87‐984‐16 ×TN93‐99 were used. Storage proteins were extracted from all RIL and separated in 10–20% linear gradient polyacrylamide gels. Dried gels were scanned for individual subunits of storage protein with a densitometer equipped with a He−Ne laser light source. Data were converted to concentration for each subunit component and analyzed using SAS software. A significant (P&lt;0.05) difference among genotypes was found for glycinin and β‐conglycinin. A total of 94 polymorphic simple sequence repeat molecular genetic markers were used in screening all RIL. Three QTL for glycinin (Satt461, Satt292, and Satt156) were distributed on linkage group (LG) D2, I, and L, respectively, whereas two QTL for conglycinin (Satt461 and Satt249) were distributed on LG D2 and J. Phenotypic variation explained by individual QTL ranged from 9.5 to 22%. These QTL may provide useful MAS opportunities for improvement of nutritional quality in soybean.

Relationship between structural changes and functional properties of soy protein isolates–carrageenan systems

The aim of this work was to study the change in the structural and functional properties of a native soy protein isolate (I) induced by the incorporation of carrageenan (C). Two types of samples were used: samples lyophilized from mixtures of I and C dispersions (IC ratio: 20:1 to 8:1), and samples prepared in situ with I and C powders (IC ratio: 5:1 to 1:1). In both kinds of I:C samples a new endotherm (DSC), which may be attributed to the IC-complex, and an increase in the thermal stability of 7S and 11S soy globulins was observed. In in situ samples, at a high ionic strength and C content, an increase in the temperature of this new endotherm was observed. 7S fraction was thought to be further involved in the formation of the complex; result confirmed through experiments carried out with 7S-C and 11S-C mixtures. The complex formation modified the pH-solubility profile of soy proteins. As the amount of C increased, a decrease in solubility—to a greater extent in the acidic zone—was observed. The loss of solubility was accompanied by a decrease in the surface hydrophobicity of soluble fractions. Electrostatic as well as hydrophobic interactions would be involved in the complex formation, depending on environmental conditions. Concerning the rheological behavior of such systems, the addition of C allowed the formation of gels of a greater gelation velocity and higher viscoelasticity compared to I dispersions. Results showed that lyophilized I:C mixtures can be employed as gelling agents with improved properties regarding independent ingredients. On the other hand, gelation of I dispersions of very low protein concentration can be performed through the addition of carrageenan in appropriate proportions.

Purification and identification of interacting components in a wheat starch–soy protein system

The objective of this research was to quantify the solubility, hydrophobicity and interaction characteristics of wheat–starch proteins (puroindoline, gliadin and glutenin) and protein-containing soy fractions (soy flour isolate [SFI], SFI 7S and 11S fractions, hexane-extracted textured soy flour [TVP] isolate, TVP 7S and 11S fractions, expelled, extruded soy flour [TSP] isolate, TSP 7S and11S fractions). Functional characteristics were assessed in aqueous sucrose solutions at pH 5.5 and 7.5 after heating to 25, 50, and 100 °C. Textured soy protein fractions were more soluble and had higher surface hydrophobicity profiles than their untextured counterparts. Sucrose addition decreased hydrophobicity in the textured proteins but increased it in untextured proteins. Characteristics of the isolate, as a whole, appear to be dictated by those of its 11S moiety. Dissociation constants ( K d values) for soy protein and starch-derived puroindoline were determined and indicated an extremely short association in all cases. The 11S fractions formed a complex with puroindoline in solution; however 7S fractions did not.

Physicochemical Modifications of High-Pressure-Treated Soybean Protein Isolates

Changes induced by high pressure (HP) treatment (200-600 MPa) on soybean protein isolates (SPI) at pH 3 (SPI3) and pH 8 (SPI8) were analyzed. Changes in protein solubility, surface hydrophobicity (Ho), and free sulfhydryl content (SH(F)) were determined. Protein aggregation and denaturation and changes in secondary structure were also studied. An increase in protein Ho and aggregation, a reduction of free SH, and a partial unfolding of 7S and 11S fractions were observed in HP-treated SPI8. Changes in secondary structure were also detected, which led to a more disordered structure. HP-treated SPI3 was partially denatured and presented insoluble aggregates. A major molecular unfolding, a decrease of thermal stability, and an increase of protein solubility and Ho were also detected. At 400 and 600 MPa, a decrease of the SH(F) and a total denaturation were observed.

Preparation and Characterization of Protein Isolate from Cowpea (Vigna unguiculata L. Walp.)

ABSTRACT: Protein isolate (PI) was prepared from 3 cowpea varieties and 2 soybean varieties in each of 2 y. The protein contents of cowpea PI (CPI) (91.4% to 91.8%) and soy PI (SPI) (93.0% to 93.5%) were significantly different (P &lt; 0.05). Electrophoretogram showed that CPI was concentrated at 60 and 40 kDa, whereas SPI showed bands at 95, 65, 60, 40, and 35 kDa. The CPI had higher lysine (49.3 to 51.8 mg/g) than SPI (41.9 to 43.4 mg/g). The CPI and SPI had surface hydrophobicities ranging from 387.8 to 572.9 and 640.6 to 643.1, respectively. Denaturation temperature (85.2 to 88.4 °C) and enthalpy (8.42 to 10.33 J/g) of CPI were similar to the 7S fraction of SPI (82.6 °C and 96.0 to 96.3 J/g). These characteristics of CPI might be useful to explain its functionalities for application in food systems.

Microarray assessment of IgE-binding proteins in lentils (Lens culinaris L.)

Rationale Proteomic technology has been shown to have distinct advantages for allergen characterization and identification. Therefore, we have used 2-D electrophoresis and protein microarrays to characterize the profile of allergens and assess their level in lentils. Methods Lentil varieties were extracted and centrifuged to obtain 2S, 7S and 11S fractions. The profile of IgE-binding proteins in these fractions was assessed using lentil-allergic sera, by immunoblotting of 2-D electrophoretic separations. The level of IgE-binding was also assessed using protein microarrays. Arrays of covalently attached proteins were first incubated with lentil-allergic sera, followed by incubation with fluorescently-labeled anti-IgE detection antibody. Laser-induced fluorescence was used to detect IgE-binding. Results Immunoblotting of electrophoretic separations showed several regions of IgE-binding that were consistently observed for all varieties. Major IgE-binding was observed for isoforms of 31 and 48 kDa spots. These proteins are of particular interest because of their low abundance, but high IgE-binding. Comparatively less IgE-binding was found for 12 and 14 kDa spots. Microarray analysis showed that IgE-binding of the 11S fraction was significantly greater than all other fractions. Microarrays enabled quantitative assessment of IgE-binding. Conclusions The application of proteomic technologies resulted in characterization of IgE-binding protein profile and determination of their level in lentils. Microarrays represent a promising tool for allergen investigation, detection and diagnosis.

The effect of autoclaving on soluble protein composition and trypsin inhibitor activity of cracked soybeans

The effects of autoclaving conditions (heating for 5, 10 and 15 minutes at 0.5 bars over pressure) and oil-extracting temperatures (40?C, 60?C) on protein content, composition, and inhibitor activity of cracked soybeans were investigated. The results obtained indicated that oil-extracting method and heat treatment had significant influence on soluble protein content and composition. Raw soybean samples defatted at lower temperature had better solubility (535.42?2.10 mg/g) than those obtained by the Soxhlet procedure (345.53?2.80). The same results were obtained for nitrogen solubility index. Autoclaving combined with two oil-extraction methods decreased protein solubility to 180.32?1.50 -245.41?1.41 mg/g, while the dominant component of heat treated flours was 11S fraction. High content of glycinin fraction (44.59-41.10%) implies the possible use of treated samples in food industry. Residual activity of treated samples was 43.40-84.26%. Kunitz inhibitor (KTI) was responsible for residual inhibitor activity.

Immunodetection of legume proteins resistant to small intestinal digestion in weaned piglets

AbstractExperiments were conducted to investigate the biochemistry of digestion of the major storage proteins from soya bean, pea, faba bean, blue lupin, and chickpea seeds in the ileum of piglets. Hyperimmune plasmas against the crude protein extracts and the purified 11S and 7S globulin fractions of each legume seed and an anti‐pea albumin PA2 and lectin antibody were used. They served to probe immunoblots of feed protein extracts and ileal digesta samples. Globally, the recognition by plasmas of intact or partially digested proteins in ileal digesta was rather faint, in agreement with the fairly high in vivo digestibility data obtained with these legume seed proteins. Nevertheless, immunoreactive polypeptides found in digesta of piglets fed pea, faba bean and chickpea belonged mainly to proteins of the 7S family, and to other proteins including low‐molecular weight components such as PA2 albumin and lectin in the case of pea. In piglets fed lupin, nearly intact polypeptides from the 11S family were detected. To conclude, the present immunochemical study conducted on ileal digesta of piglets revealed a few dietary legume proteins of the vicilin and albumin families. Legumin proteins were demonstrated unequivocally in the case of lupin and white chickpea. Copyright © 2003 Society of Chemical Industry

Functional properties of soy protein fractions produced using a pilot plant‐scale process

AbstractSoy proteins fractionated by the modified Nagano process (Nagano method) and a simplified pilot‐plant process (CCUR method) were studied for their functional properties, including solubility, viscosity, emulsification, and foaming. The functional properties of the three fractions produced by the Nagano method—glycinin (11S), β‐conglycinin (7S), and an intermediate fraction (IM)—were studied under a selected range of pH, ionic strengths, and protein concentrations. The 11S fraction was more soluble than the 7S at pH 2–3, whereas the 7S was more soluble than 11S at pH 5–6. Adding NaCl changed the solubility of both fractions at pH 4–5 compared to a neutral pH. Other functional properties were related to solubility in the 7S and 11S fractions. The CCUR method yielded only two fractions, 11S and 7S, and the functionality of those fractions was tested at a neutral pH. The solubility of the CCUR samples was slightly higher at extreme pH levels compared to 11S and 7S fractions from the Nagano method at a neutral pH. The relationship between solubility and other functional properties was clearer in CCUR samples. These results indicate that the simplified pilot‐scale CCUR fractionation process can influence the functional properties of the protein fractions.

Functional properties of the acidic and basic subunits of the glycinin (11S) soy protein fraction

AbstractThe functional properties of low‐ and high‐M.W. (LMW and HMW, respectively) acidic subunits and the basic subunit separated from the 11S soy protein fraction were studied and compared with the functional properties of the 11S fraction. Among the functional properties investigated were solubility, emulsification, and viscosity. The results showed that the LMW acidic subunit had higher solubility than the HMW acidic subunit. Among all the samples, the LMW subunit separated by using β‐mercaptoethanol (ME) was the most soluble, with a solubility of 98–100% at a pH of 6–12. The solubility profile of the HMW subunit followed a pattern similar to the solubility of 11S. The lowest solubility was observed around pH values in the range close to the isoelectric point for both the LMW and HMW subunit. The basic subunit was not soluble in the pH range 3–10; however, the solubility increased more than 50% at pH 13 compared to the solubility at pH 10. The emulsification capacity of all subunits was higher than 11S in the following descending order: LMW, basic, HMW, 11S. Emulsification activity and stability of the subunits were greater than those of the 11S samples at room temperature and 95°C. With the exception of the LMW subunit separated with ME, the subunits had a higher viscosity than 11S. The basic subunit separated with sodium bisulfite had the highest viscosity of all the samples tested.

Improvement of emulsifying properties of lupin proteins by high pressure induced aggregation

Aggregation of lupin ( Lupinus albus) proteins induced by high-pressure treatment has been investigated in relation with their interfacial and emulsifying properties. Proteins were extracted from lupin meal in Tris–HCl buffer at pH 7.0 and pressurised at 15 g/l prior to emulsion preparation. High-pressure conditions were 200, 400 and 600 MPa for 10 min at 10 °C. Oil-in-water emulsions (30% oil fraction) were prepared with valve homogeniser at 20 MPa. Interfacial and emulsifying properties (oil droplets size, emulsion stability, interfacial protein concentration and rheological behaviour) were evaluated. Size chromatography exclusion studies on lupin proteins indicated that 11S (α-conglutin) fraction was extensively aggregated after a pressure treatment higher than 400 MPa. A decrease of protein solubility was concurrently revealed, indicating a partial dissociation of monomers. High pressure (400 MPa) treated lupin proteins gave emulsions with lower values of droplet size, an increase of interfacial protein concentration (mg/m 2) and a decrease of creaming and flocculation index as compared to control proteins. Therefore the sodium dodecyl sulfate (SDS)-electrophoresis patterns of adsorbed and non-adsorbed proteins in the interfacial film showed that proteins could be selectively adsorbed according to pressure treatment. This study has shown the improvement of emulsifying properties of lupin proteins from high-pressure treatment at 400 MPa.

Characterization of storage proteins in different soybean varieties and their relationship to tofu yield and texture

The contribution of the total soybean proteins, the storage proteins [glycinin (11S) and β-conglycinin (7S) fractions] and their respective subunits to tofu yield and texture was studied. Protein contents were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) coupled with densitometry and reversed phase-high performance liquid chromatography (RP-HPLC), for seven soybean varieties, and correlated to tofu yield and texture. Results from SDS-PAGE, coupled with densitometry, showed that the 11S fraction proteins ( r=0.863, P<0.01), the α′ polypeptide of 7S ( r=0.917, P<0.01) and the basic polypeptide of 11S ( r=0.775, P<0.01) appeared to each affect tofu yield; however, no relationship between storage protein fractions and tofu firmness was observed. On the other hand, the RP-HPLC profiles of the total soybean proteins and the 11S and 7S fractions indicated relationships between tofu firmness and the 11S fraction, the 7S fraction, and their ratio. The inverse correlation ( r=−0.832, P<0.01) between peak 7 of the 7S fraction and tofu firmness seems to point toward its important role in defining tofu quality.