Yam Tuber Storage Protein Reduces Plant Oxidants Using the Coupled Reactions as Carbonic Anhydrase and Dehydroascorbate Reductase

Investigating the impact of ultrasound on the structural, physicochemical, and emulsifying characteristics of Dioscorin: Insights from experimental data and molecular dynamics simulation

This study investigated the impact of ultrasound treatment on dioscorin, the primary storage protein found in yam tubers. Three key factors, namely ultrasound power, duration, and frequency, were focused on. The research revealed that ultrasound-induced cavitation effects disrupted non-covalent bonds, resulting in a reduction in α-helix and β-sheet contents, decreased thermal stability, and a decrease in the apparent hydrodynamic diameter (Dh) of dioscorin. Additionally, previously hidden amino acid groups within the molecule became exposed on its surface, resulting in increased surface hydrophobicity (Ho) and zeta-potential. Under specific ultrasound conditions (200 W, 25 kHz, 30 min), Dh decreased while Ho increased, facilitating the adsorption of dioscorin molecules onto the oil-water interface. Molecular dynamics (MD) simulations showed that at lower frequencies and pressures, the structural flexibility of dioscorin's main chain atoms increased, leading to more significant fluctuations between amino acid residues. This transformation improved dioscorin's emulsifying properties and its oil-water interface affinity.

Revealing the mechanism underlying the effects of γ-aminobutyric acid-dioscorin interactions on dioscorin structure and emulsifying properties by molecular dynamic simulations

Many studies have shown that γ-aminobutyric acid (GABA) exhibits various beneficial biological activities, including gut-modulating, neuro-stimulating, and cardio-protecting activities. Naturally, GABA exists in small amounts in yam, which is primarily synthesized by the decarboxylation of L-glutamic acid in the presence of glutamate decarboxylase. Dioscorin, the major tuber storage protein of yam, has been shown to have good solubility and emulsifying activity. However, how GABA interacts with dioscorin and affects their properties has yet to be clarified. In this research, the physicochemical and emulsifying properties of GABA-fortified dioscorin, which was dried by spray drying and freeze drying, were studied. As results, the freeze-dried (FD) dioscorin produced more stable emulsions, while the spray-dried (SD) dioscorin adsorbed more rapidly to oil/water (O/W) interface. The fluorescence spectroscopy, ultraviolet spectroscopy and circular dichroism spectroscopy showed that GABA changed the structure of dioscorin, by exposing its hydrophobic groups. The addition of GABA significantly promoted the adsorption of dioscorin to the O/W interface and prevented droplets coalescence. The results of molecular dynamics simulation (MD) showed that GABA destroyed the H-bond network between dioscorin and water, increased surface hydrophobicity and finally improved the emulsifying properties of dioscorin.

Effects of spray drying and freeze drying on the structure and emulsifying properties of yam soluble protein: A study by experiment and molecular dynamics simulation

This study focused on the effects of freeze drying (FD) and sprays drying (SD) on the structure and emulsifying properties of yam soluble protein (YSP). The results showed that the surface hydrophobicity (Ho) value, free sulfhydryl group (SH) content, turns content, denaturation temperature and enthalpy value of spray-dried YSP (SD-YSP) were higher than freeze-dried YSP (FD-YSP), but the apparent hydrodynamic diameter (Dh) value of SD-YSP was smaller. The smaller Dh, higher Ho and free SH led to higher percentage of adsorbed proteins and stronger binding between protein and oil droplet in emulsions. Thus, the emulsifying properties of SD-YSP were better, and the SD-YSP-stabilized emulsion had better dynamical rheological properties. Molecular dynamics (MD) simulations suggested that some intramolecular disulfide bonds and hydrogen bonds of dioscorin were broken, and some helices transformed into turns during the SD process. These structural changes resulted in better thermal stability and emulsification properties of SD-YSP.

Immunity-Enhancing Effect of Extracts Extracted from Leaves of Rubia hexaphylla, Cymbopogon citratus, and Dioscorea japonica for Sustainable Healthy Life

The COVID-19 era requires research and development into eco-friendly immune technologies in human life. However, such research is limited because of a lack of interest. Therefore, in this study, sub-critical extracts extracted from Rubia hexaphylla leaves, Cymbopogon citratus, and Dioscorea japonica with physiological effects were tested for their ability to enhance immunitye and antioxidant activity in the body. Cell viability experiments, cytokine secretion induction experiments, nitrogen oxide induction experiments, and cytokine content measurements in mouse serum and NK activation experiments were conducted to verify the effects of improving immunitye and antioxidant activity in the body. First, the cell survival rate of all samples was found to be over 95%. Second, it was confirmed that the contents of IL-6 and TNF-α in the macrophages of all samples were increased, especially for RCD 3, at concentrations of 1000 μg/mL. Third, the nitrogen oxide content of all samples was increased in the nitrogen oxide induction evaluation, especially for RCD 3, at the highest concentration of 1000 μg/mL. Fourth, for RCD 3, IL-2 and TNF-γ were the highest measured in the measurement of the cytokine content in the mouse serum. Fifth, in the NK activation experiments, the positive control group of the samples was all found to have higher activity than the negative control group, with more than 60% cell activity in RCD 3.

Thiol Redox Regulation of Plant β-Carbonic Anhydrase

β-carbonic anhydrases (βCA) accelerate the equilibrium formation between CO2 and carbonate. Two plant βCA isoforms are targeted to the chloroplast and represent abundant proteins in the range of >1% of chloroplast protein. While their function in gas exchange and photosynthesis is well-characterized in carbon concentrating mechanisms of cyanobacteria and plants with C4-photosynthesis, their function in plants with C3-photosynthesis is less clear. The presence of conserved and surface-exposed cysteinyl residues in the βCA-structure urged to the question whether βCA is subject to redox regulation. Activity measurements revealed reductive activation of βCA1, whereas oxidized βCA1 was inactive. Mutation of cysteinyl residues decreased βCA1 activity, in particular C280S, C167S, C230S, and C257S. High concentrations of dithiothreitol or low amounts of reduced thioredoxins (TRXs) activated oxidized βCA1. TRX-y1 and TRX-y2 most efficiently activated βCA1, followed by TRX-f1 and f2 and NADPH-dependent TRX reductase C (NTRC). High light irradiation did not enhance βCA activity in wildtype Arabidopsis, but surprisingly in βca1 knockout plants, indicating light-dependent regulation. The results assign a role of βCA within the thiol redox regulatory network of the chloroplast.

Physicochemical, enzymatic and molecular characterisation of the storage protein of aerial tuber, Dioscorea bulbifera Linn

BACKGROUND

The storage protein of the aerial tuber of Dioscorea bulbifera was purified and its physicochemical, enzymatic and molecular properties determined with a view to comparing its functionality and genetic relatedness with other storage proteins.

RESULTS

The purified protein had molecular weight of 21 kDa. The protein showed carbonic anhydrase, trypsin inhibitory, dehydroascorbate reductase and monodehydroascorbate reductase activities. Amplifications with polymerase chain reactions resulted in the detection of two genes encoding the storage protein. The deduced amino acid sequence of the shorter and larger genes had homologies with the storage proteins of members of the Dioscorea family.

CONCLUSION

The study concluded that the storage protein of the aerial tuber of D. bulbifera had similar properties with those of other Dioscorea species and may be suitable for development as functional food.

Solubility and emulsifying activity of yam soluble protein

Yam soluble protein (YSP) has been reported to have many physiological activities, such as scavenging free radicals, immune activation, and anti-hypertensive activities. Protein solubility and emulsifying activity are important protein-associated functional properties for the application of proteins in food systems. During this study, the factors of protein concentration, pH, temperature and salt concentration that influenced the solubility of YSP were investigated. As a result, the solubility was minimal near its isoelectric point (pH 3.5) and was highest at 45 °C in a temperature range of 40-60 °C. With an increase of protein concentration, the solubility decreased. According to the results of response surface methodology analysis, the interaction between pH and temperature on the solubility of YSP was significant, and the maximum solubility (87.5%) was obtained when the temperature was close to 40 °C, the pH was approximately 7 and the NaCl concentration approached 0.5 mol/L. As the protein concentration increased, the average particle size of the YSP emulsion decreased, and the particle size distribution gradually became balanced. Additionally, the microphotograph of the YSP emulsion reflected its distribution. The results of this study will provide data and a theoretical basis for the understanding of YSP's physicochemical properties and its application in the food industry.

Recovery of Yam Soluble Protein from Yam Starch Processing Wastewater

Over the past two decades, many studies have shown that the yam storage protein dioscorin, which is abundant in the wastewater of starch processing, exhibits many biological activities both in vitro and in vivo. In the present study, the acid-precipitation method was optimized using Box-Behnken design (BBD) combined with response surface methodology (RSM) for the recovery of yam soluble protein (YSP) from wastewater. The experimental yield of YSP reached 57.7%. According to relative quantitative proteomics (LC-MS/MS), the crude YSP was mainly composed of 15 dioscorin isoforms, which was further verified by anion-exchange and size-exclusion chromatography. YSP was found to be rich in glutamic acid and aspartic acid, and the eight essential acids made up approximately 33.7% of the YSP. Moreover, the YSP demonstrated antioxidant activity, including scavenging DPPH, hydroxyl and superoxide anion radicals, and the possible structure-activity relationships were discussed. These results indicated that YSP produced by acid precipitation may be used as a protein source with antioxidant properties.

Yellow pigment formation, pigment composition, and quality of fresh-cut yam (Dioscorea opposita) slices

Fresh-cut yam (Dioscorea opposita) slices brown easily and can turn yellow under certain storage conditions. The formation conditions of yellow pigment, pigment composition, and quality of yellow fresh-cut yam slices were investigated in this study. The results showed that storage temperature, gas ratio of packaging, and slice thickness affected the formation of yellow pigmentation. The highest content of yellow pigment was found in 0.1 cm-thick yam slices stored at 25 °C for 18 h and packaged in 20% O₂ and 80% N₂. Yellow pigments were composed primarily of bisdemethoxycurcumin (73.7%) and two other unknown compounds that were not attributed to microorganisms. Yellow fresh-cut yam exhibited good quality, and the alcohol and ester extracts of yellow yams had higher oxygen radical adsorption capacity and 2,2-diphenyl-1-picrylhydrazyl radical scavenging ability compared to white fresh-cut yam.

Fresh-cut yam (Dioscorea opposita) slices brown easily and can turn yellow under certain storage conditions.

Functional properties of Chinese yam (Dioscorea opposita Thunb. cv. Baiyu) soluble protein

In this study, yam soluble protein (YSP) was extracted from Chinese yam (Dioscorea opposita Thunb. cv. Baiyu) and the functional properties were investigated under the influence of pH and ionic strength. As results, YSP was highly soluble and had better emulsifying activity over a wide range of pH. The solubility of YSP decreased in 0.5 and 1.0 M NaCl solution. An increment in NaCl concentration reduced the emulsion activity index and emulsion stability index of YSP. The oil absorption capacity of YSP was 3.2 ml/g protein. With the increase of pH, the foam capacity (FC) and stability (FS) decreased and then increased. FS of YSP increased as the salt concentration increased from 0 to 0.5 M, and then decreased. The minimal gelation concentration of YSP was 8% (w/v) and 10% YSP gel (w/v) had maximum gel strength in 0.1 M NaCl. These results suggested that YSP produced by acid precipitation may be used as a protein source with remarkable functional properties.

Expect the Unexpected Enrichment of "Hidden Proteome" of Seeds and Tubers by Depletion of Storage Proteins

Dynamic resolution of seed and tuber protein samples is highly limited due to the presence of high-abundance storage proteins (SPs). These proteins inevitably obscure the low-abundance proteins (LAPs) impeding their identification and characterization. To facilitate the detection of LAPs, several methods have been developed during the past decade, enriching the proteome with extreme proteins. Most of these methods, if not all, are based on the specific removal of SPs which ultimately magnify the proteome coverage. In this mini-review, we summarize the available methods that have been developed over the years for the enrichment of LAPs either from seeds or tubers. Incorporation of these methods during the protein extraction step will be helpful in understanding the seed/tuber biology in greater detail.