Structural and Functional Analysis of Various Globulin Proteins from Soy Seed

Storage proteins of soybean mostly consist of globulins, which are classified according to their sedimentation coefficient. Among 4 major types: 2S, 7S, 11S, and 15S of globulins, 7S and 11S constitute major fraction. The 11S fraction consists only of glycinin and 7S fraction majorly consists of β-conglycinin, small amounts of γ-conglycinin and basic 7S globulin (Bg7S). Glycinin exist as a hexamer while β-conglycinin as a trimer and Bg7S as a tetramer. Glycinin subunits are coded by 5 genes of a family, whereas about 15 genes are present for β-conglycinin subunits. Bg7S gene is present in four copies in soybean genome. Synthesis of all proteins takes place as a single polypeptide chain, which is cleaved after folding to yield different chains or subunits. Glycinin and β-Conglycinin are made for storage purpose. However, Bg7S has potential xylanase inhibition activity and protein kinase activity. Primary structure of Bg7S reveals 12 conserved cysteine residues involved in forming 6 disulfide bonds, which provides appreciable stability to protein. Secondary structure is predominately rich in β-sheets with few alpha helices. Bg7S shares structural similarity with various aspartic-proteases. In this review, our aim is to discuss sequence, structure, and function of various globulins present in Glycine max.     

Functional properties of 8S globulin fractions from 15 mung bean (Vigna radiata (L.) Wilczek) cultivars

The functional properties including solubility, water absorption capacity, oil absorption capacity, foaming properties and emulsifying properties of 8S globulin fractions from 15 mung bean cultivars were investigated in this study. In addition, the effects of pH on solubility, foaming properties and emulsifying properties were studied. The functional properties of the 8S globulin fractions varied significantly among the different mung bean varieties and exhibited better performance in solubility and emulsion stability compared with soya bean 7S protein. A negative correlation was found between water absorption capacity and oil absorption capacity. Remarkable differences in polypeptides constituents were observed in 8S globulin fractions, and the ratio of 11S/8S globulins has a positive effect on water absorption capacity while a negative effect on oil absorption capacity. As a function of pH, the emulsifying activity indexes of the 8S globulin fractions were found to be distinctly dependent on the solubility, while no significant correlation was found between the emulsifying stability and solubility, nor between the foaming properties and solubility. The foaming capacity showed a strong correlation with foam stability.     

Oligopeptide patterns produced from Theobroma cacao L of various genetic origins

Acetone dry powder (AcDP) was prepared for six cocoa genotypes, namely Forastero (Amelonado type), Criollo, Trinitario, SCA 12, UIT1 and PBC 140. Hydrophobic oligopeptides were produced when autolysis of AcDP was carried out at pH 3.5. Comparative HPLC analysis showed that autolysis of AcDP from various genotypes revealed a similar pattern of oligopeptides. Most of the hydrophobic oligopeptides were not generated during autolysis of AcDP in the presence of protease inhibitor (Pepstatin A), indicating that the generation of these oligopeptides was due to the action of cocoa cotyledon aspartic endoprotease. This finding implies that the splitting action of aspartic endoprotease on vicilin (7S)‐class globulin (VCG) from various genotypes was the same. The information from the study provides additional evidence that there are no obvious differences in VCG composition between various genotypes. © 2002 Society of Chemical Industry     

罗望子种仁球蛋白-EGCG共价复合物的制备及其在乳化香肠中的应用

通过碱处理法制备罗望子种仁球蛋白（tamarind seed globulin,TSG）-表没食子儿茶素没食子酸酯（(-)-epigallocatechin-3-gallate,EGCG）共价化合物,采用紫外-可见光谱分析TSG-EGCG共价复合物结合率并优化结合条件。采用色差计、质构分析仪和扫描电子显微镜研究TSG-EGCG共价复合物添加量对乳化香肠蒸煮损失、保水性和质构的影响。结果表明：当TSG与EGCG质量比1∶0.1、反应pH 9.5、反应温度30℃时,复合物的结合率达到最大值。与添加TSG的乳化香肠相比,添加TSG-EGCG复合物的乳化香肠微观结构更加紧密,立体凝胶网络更加均匀清晰,同时蒸煮损失率、保水性及质构特性得到明显改善。综上,TSG-EGCG复合物可以改良乳化香肠的感官品质,且当添加量为2%时,乳化香肠的品质得到明显改善。     

Crystal structure of a major seed storage protein, 11S proglobulin, from Amaranthus hypochondriacus: insight into its physico-chemical properties

Amaranth is a crop known for its high quality proteins. 11S Globulin is one of the most abundant and important storage proteins of the amaranth grain. Here, we report the crystal structure of amaranth 11S proglobulin at a final resolution of 2.28 Å. It belonged to the space group P6₃ with cell dimensions a = b = 96.6, c = 75.0 Å. It contains one asymmetric unit consisting of 372 residues and 100 water molecules. Disordered regions in the model approximately correspond to the variable regions of the 11S globulins. The structure has an extended α-helix and β-barrel domains at both N-terminal and C-terminal regions, which are characteristic of the 11S and 7S globulins. The three dimensional structure suggests that its high thermal stability is due to the cumulative effects of many factors and its good emulsifying property depended on the balance between its surface hydrophobicity and hydrophilicity.     

Structure–physicochemical function relationships of 7S globulins (vicilins) from red bean (Phaseolus angularis) with different polypeptide constituents

Red bean 7S globulins (vicilins) with different polypeptide constituents or heterogeneity were fractionated using acidic extraction (at 0.5 M NaCl) and anion-exchange column chromatography. The physicochemical and conformational properties, including amino acid composition, net charge and/or surface hydrophobicity (H₀), protein solubility (PS), thermal and emulsifying properties, as well as secondary, tertiary and/or quaternary conformations, were evaluated. There were distinct differences in zeta potential, H₀, DSC characteristics, emulsifying activities and tertiary and/or quaternary conformations among the vicilins with different polypeptide constituents, but the PS and secondary conformation were slightly different. The PS as a function of pH and thermal stability were closely related to their surface charge and/or hydrophobicity. The emulsifying ability and the emulsion stability were closely dependent on the PS and H₀, and even the flexibility in tertiary and/or quaternary conformations. These results suggested good relationships between the physicochemical functions and conformational features of red bean vicilins, which could be of great help for further utilization of legume proteins as a potential functional ingredient.     

Binding of aroma compounds with legumin. III. Thermodynamics of competitive binding of aroma compounds with 11S globulin depending on the structure of aroma compounds

This paper considers the prominent features in competitive binding of aroma esters from their mixtures to 11S globulin of broad beans (legumin) in aqueous medium at pH 7.2 and ionic strength of 0.05 mol dm⁻³. Series of alkyl acetates (C₄–C₈) and methyl esters of carbonic acids (C₅–C₉), differing in the length of hydrocarbon chain, have been under our studying. To accomplish the ends of the study, a combination of ultrafiltration and gas–liquid chromatography (GC) has been used. An increase in the length of hydrocarbon chain of the aroma esters brought about greater binding affinity for the protein, the occurrence of some structural restrictions in the interior of the protein molecule, preventing binding, and the change in the binding mechanism of the aroma compounds at the specific critical length of hydrocarbon chain. Differential scanning microcalorimetry data suggested that the revealed changes in the binding mechanism of the studied aroma compounds were attributable to the conformational modification of the protein globule as a result of binding with the aroma compounds. A distinguishing feature in binding of methyl esters of carbonic acids with legumin was their greater binding affinity for the protein as compared with alkyl acetates. The mutual effect of aroma compounds on binding from their equimolar mixtures to the protein made itself evident, firstly, as a drastic increase in the binding extent of aroma esters, having rather long hydrocarbon chain and, secondly, as a dramatic change in the binding mechanism of the aroma esters with relatively short hydrocarbon chain.     

Enzymatic preparation of immunomodulatory hydrolysates from defatted wheat germ (Triticum Vulgare) globulin

Defatted wheat germ globulin (DWGG) was hydrolysed using the enzymes alcalase, neutrase, papain, pepsin or trypsin to improve the immunomodulatory effects of the protein. The degree of hydrolysis (DH), molecular weight distribution, hydrophobicity, secondary structures and immunomodulatory activities were determined. The DH of hydrolysate using alcalase or neutrase was higher (P < 0.05) than that of hydrolysate prepared by other proteases. Alcalase hydrolysate (AH) had the strongest (P < 0.05) immunomodulatory activity with respect to lymphocyte proliferation, phagocytosis of neutral red and secretion of pro‐inflammatory cytokines. The molecular weight of AH ranged between 300 and 1450 Da and was composed of α‐helix and β‐turns. AH also showed the highest hydrophobic value (P < 0.05). The DH and hydrophobicity appear to be related to immunomodulatory activities. The hydrolysate prepared by the alcalase treatment on DWGG may be used as an immune supplement by the food industry.     

大豆球蛋白和清蛋白水法提取工艺研究

采用水法从低温豆粕和高温豆粕中提取球蛋白和清蛋白,通过单因素实验和正交实验对提取工艺进行优化,并研究了pH对蛋白质提取率的影响。结果表明:低温豆粕和高温豆粕清蛋白水法提取的最佳工艺条件为料液比1∶12、提取时间2.0 h、提取温度45℃,此时清蛋白提取率分别为66.41%、24.89%;低温豆粕球蛋白水法提取的最佳工艺条件为料液比1∶8、提取时间3.0 h、提取温度50℃、Na Cl溶液质量分数4%,此时球蛋白提取率为21.86%;高温豆粕球蛋白水法提取的最佳工艺条件为料液比1∶14、提取时间2.0 h、提取温度50℃、Na Cl溶液质量分数4%,此时球蛋白提取率为16.98%。在最佳工艺条件下,pH在7~11时低温豆粕清蛋白提取率分别提高了0.65、4.99、10.59、8.91、10.99个百分点,pH在8~11时高温豆粕清蛋白提取率分别提高了2.46、10.29、26.24、37.86个百分点,pH在4~6时低温豆粕和高温豆粕球蛋白提取率分别提高了7.74、13.30、2.94个百分点和4.45、5.13、3.27个百分点。