Acidic Subunit Research Articles

Osborne extractability and chromatographic separation of protein from quinoa (Chenopodium quinoa Willd.) wholemeal

The composition of quinoa proteins has hardly been studied. We here applied an Osborne type extraction procedure. High protein yield and little protein denaturation was obtained with extraction (2x) with water followed by extraction (2x) with 0.4 mol/l sodium chloride. Albumins, globulins, prolamins and glutelins accounted for 41–50, 7–11, 4–6 and 14–16% of the total protein of four quinoa cultivars, respectively. Protein extracts were separated by size exclusion high performance liquid chromatography (SE-HPLC) with a sodium dodecyl sulfate containing elution medium. Electrophoretic separation followed by mass spectrometry allowed identifying the proteins in the Osborne type extracts. Aqueous extracts contained different chloroplastic and cytoplasmic enzymes as well as legumin-like and vicilin-like proteins. Dilute salt extracts mainly contained legumin-like proteins. Aqueous alcohol extracts contained small proteins while dilute base extracts proteins were similar to those present in the aqueous and dilute salt extracts. In one cultivar, only the monomer of the 11S globulin seed storage protein 2-like was observed while the other cultivars studied also contained its acidic and basic subunits separately. This SE-HPLC method allows analyzing food processing induced changes in quinoa protein extractability and size distribution.

Rapid detection of an I38T amino acid substitution in influenza polymerase acidic subunit associated with reduced susceptibility to baloxavir marboxil.

BackgroundThe novel cap‐dependent endonuclease inhibitor baloxavir marboxil was approved in February 2018 for the treatment of influenza virus infection in Japan. In vitro studies have revealed that an I38T substitution in the polymerase acidic subunit (PA) is associated with reduced susceptibility of influenza viruses to baloxavir.ObjectivesDevelopment of a rapid and simple method for monitoring influenza A(H1N1)pdm09, A(H3N2), and B viruses possessing the I38T substitution in PA.MethodsThree assays were developed based on RNase H2‐dependent PCR (rhPCR) and named A/H1pdm PA_I38T rhPCR, A/H3 PA_I38T rhPCR, and B PA_I38T rhPCR. The assays were evaluated using cDNAs synthesized from in vitro‐transcribed PA gene RNA controls, RNAs purified from viruses isolated in the 2017/2018 and 2018/2019 influenza seasons, and RNAs purified from clinical specimens collected in the 2018/2019 influenza season.ResultsThe assays developed in this study accurately discriminated PA I38 and PA T38 with high sensitivity.ConclusionsOur assays should be considered a powerful tool for monitoring the emergence of baloxavir‐resistant influenza viruses.

Modification of soy protein isolates using combined pre-heat treatment and controlled enzymatic hydrolysis for improving foaming properties

The foaming properties of soy protein hydrolysates modified with a combination of pre-heat treatment and controlled enzymatic hydrolysis by pepsin were investigated. Degree of hydrolysis, soluble protein percentage, peptide profile, molar mass distribution, surface properties at air-water interface and interfacial rheological properties of hydrolysates were measured to gain insights into the relationships between molecular composition and foaming properties. It was found that pre-heat treatment of soy protein at 55 °C for 30 min promoted the hydrolysis of hydrophilic acidic subunits and increased the ratio of 7S/11S. As a result, it resulted in the best interfacial properties and foam capacity as well as stability amongst all treatments. Although pre-heat treatment above 65 °C before soy protein isolate hydrolysis increased degree of hydrolysis, higher proportion of large protein aggregates in the hydrolysates with increasing temperature deteriorated their foaming capacity and stability due to the lower storage modulus (G′) of the adsorbed layers and less surface excess concentration (Γ) compared to the hydrolysate with pre-heat treatment at 55 °C. Without pre-heat treatment, unfolded soy protein did not provide sufficient accessible sites for pepsin hydrolysis. As a result, foam capacity and stability of non-preheat treatment hydrolysate were inferior to those of 55 °C pre-heat treatment hydrolysate. This study provided the foundation for the application of soy protein isolate in aerated food products with desirable foaming properties.

Engineered protein containing crotoxin epitopes induces neutralizing antibodies in immunized rabbits

Crotoxin (Ctx) is the main lethal component of Crotalus durissus terrificus venom. It is a neurotoxin, composed of two subunits associated by noncovalent interactions, the non-toxic acid subunit (CA), named Crotapotin, and the basic subunit (CB), with phospholipase A2 (PLA2) activity. Employing the SPOT synthesis technique, we determined two epitopes located in the C-terminal of each Ctx subunit. In addition, 3 other epitopes were mapped in different regions of Ctx using subcutaneous spot implants surgically inserted in mice. All epitopes mapped here were expressed together as recombinant multi-epitopic protein (rMEPCtx), which was used to immunize New Zealand rabbits. Anti-rMEPCtx rabbit serum cross-reacted with Ctx and crude venoms from C. d. terrificus, Crotalus durissus ruruima, Peruvian C. durissus and Bothrops jararaca (with lower intensity). Furthermore, anti-rMEPCtx serum was able to neutralize Ctx lethal activity. As the recombinant multiepitopic protein is not toxic, it can be administered in larger doses without causing adverse effects on the immunized animals health. Therefore, our work evidences the identification of neutralizing epitopes of Ctx and support the use of recombinant multiepitopic proteins as an innovation to immunotherapeutics production.

The role of soy protein degradation caused by spoilage Bacillus amyloliquefaciens in texture deterioration of yuba, a soy product

Bacillus spp. are the dominant spoilage organisms in a rehydrated non-fermented soy product, Sichuan yuba in China. In this study, we used two spoilage Bacillus amyloliquefaciens strains DY1a and DY1b to evaluate their destructive capability on rehydrated Sichuan yuba at 25 °C. Compared with the uninoculated soy product, the texture profile of the inoculated samples showed that the hardness, springiness, chewiness, and cohesiveness decreased significantly. Scanning electron microscope (SEM) revealed that the surface of bacteria-inoculated soy product was scattered with deep holes and loose film network structure. The subsequent analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated that the α and α’ subunit of 7S globulin and the acid subunit of 11S glycinin were hydrolyzed by Bacillus during storage. In addition, disulfide bond contents in inoculated samples decreased by 38.7–27.5%. Protein secondary structure characterized using Fourier transform infrared spectroscopy (FTIR) revealed that spoilage Bacillus inoculation reduced the β-sheet by 13.02–14.11%, and increased the β-turn by 15.55–16.00%. Consequently, the texture deterioration of Sichuan yuba was associated with soy protein degradation caused by B. amyloliquefaciens.

Physicochemical properties of proteins extracted from four new Tennessee soybean lines

Physicochemical properties of soy proteins extracted from check soybean cultivar 5601T and four new Tennessee soybean lines TN03-349, TN04-5321, TN08-002, and TN08-015 were compared. The protein extracted from 5601T had the lowest content of total protein and the lowest denaturation temperature and enthalpy (P < 0.05). The lowest solubility was observed at pH 5.0 for 5601T, TN04-5321, and TN03-349, while it was at pH 6.0 for the other two, which agreed with zeta-potential data. TN04-5321 and TN08-002 extract powder had a higher content of total protein than the other three (P < 0.05). The TN04-5321 extract was absent in an acidic glycinin subunit which may be the cause of its best gelation properties. Despite difficulties in correlating structure and functionality, it was noted that the gel formed from TN04-5321 with CaCl2 at pH 7 was 6 times stronger than that of 5601T, which may be significant to bean curd products.

Global update on the susceptibilities of human influenza viruses to neuraminidase inhibitors and the cap-dependent endonuclease inhibitor baloxavir, 2017–2018

The global analysis of neuraminidase inhibitor (NAI) susceptibility of influenza viruses has been conducted since the 2012–13 period. In 2018 a novel cap-dependent endonuclease inhibitor, baloxavir, that targets polymerase acidic subunit (PA) was approved for the treatment of influenza virus infection in Japan and the United States. For this annual report, the susceptibilities of influenza viruses to NAIs and baloxavir were analyzed.A total of 15409 viruses, collected by World Health Organization (WHO) recognized National Influenza Centers and other laboratories between May 2017 and May 2018, were assessed for phenotypic NAI susceptibility by five WHO Collaborating Centers (CCs). The 50% inhibitory concentration (IC50) was determined for oseltamivir, zanamivir, peramivir and laninamivir. Reduced inhibition (RI) or highly reduced inhibition (HRI) by one or more NAIs was exhibited by 0.8% of viruses tested (n = 122). The frequency of viruses with RI or HRI has remained low since this global analysis began (2012–13: 0.6%; 2013–14: 1.9%; 2014–15: 0.5%; 2015–16: 0.8%; 2016–17: 0.2%). PA gene sequence data, available from public databases (n = 13523), were screened for amino acid substitutions associated with reduced susceptibility to baloxavir (PA E23G/K/R, PA A36V, PA A37T, PA I38F/M/T/L, PA E119D, PA E199G): 11 (0.08%) viruses possessed such substitutions. Five of them were included in phenotypic baloxavir susceptibility analysis by two WHO CCs and IC50 values were determined. The PA variant viruses showed 6–17-fold reduced susceptibility to baloxavir. Overall, in the 2017–18 period the frequency of circulating influenza viruses with reduced susceptibility to NAIs or baloxavir was low, but continued monitoring is important.

Potential Role of Endonuclease Inhibition and Other Targets in the Treatment of Influenza.

Influenza is a single-stranded RNA virus that is highly contagious and infects millions of people in the U.S. annually. Due to complications, approximately 959,000 people were hospitalized and another 79,400 people died during the 2017-2018 flu season. While the best methods of prevention continue to be vaccination and hygiene, antiviral treatments may help reduce symptoms for those who are infected. Until recently, the only antiviral drugs in use have been the neuraminidase inhibitors: oseltamivir, zanamivir, and peramivir. We reviewed novel drug targets that can be used in the treatment of influenza, particularly in the case of neuraminidase inhibitor-resistant strains that may emerge. More recently, a drug with a new mechanism of action has been approved. Baloxavir marboxil inhibits the influenza cap-dependent endonuclease that is needed for the virus to initiate replication within the host cell. This endonuclease target is within the polymerase acid (PA) subunit of RNA polymerase. Since the RNA-dependent RNA polymerase consists of two other subunits, polymerase basic 1 and 2, RNA polymerase has several targets that prevent viral replication. Other targets still under investigation include viral kinases, endocytosis, and viral fusion. Due to the possibility of viral mutations and resistance, it is important to have antivirals with different mechanisms available, especially in the case of a new pandemic strain. Several novel antivirals are within various stages of development and may represent new classes of treatments that can reduce symptoms and complications in those patients who may be at higher risk.

ATP gatekeeper of Plasmodium protein kinase may provide the opportunity to develop selective antimalarial drugs with multiple targets

Malaria is one of the most devastating infectious diseases that caused millions of clinical cases annually despite decades of prevention efforts. Recent cases of Plasmodium falciparum resistance against the only remaining class of effective antimalarial (artemisinin) in South East Asia may soon pose a significant threat. Hence, the identification of new antimalarial compounds with a novel mode of action is necessary to curb this problem. Protein kinase has been implicated as a valid target for drug development in diseases such as cancer and diabetes in humans. A similar approach is now recognized for the treatment of protozoan-related disease including malaria. Few Plasmodium protein kinases that are not only crucial for their survival but also have unique structural features have been identified as a potential target for drug development. In this review, studies on antimalarial drug development exploiting the size of Plasmodium protein kinase ATP gatekeeper over the past 15 years are mainly discussed. The ATP-binding site of Plasmodium protein kinases such as Pf CDPK1, Pf CDPK4, Pf PKG, Pf PK7, and Pf PI4K showed great potential for selective and multi-target inhibitions owing to their smaller or unique ATP-gatekeeper amino acid subunits compared to that of human protein kinase. Hence it is a feasible solution to identify a new class of active antimalarial agents with a novel mode of action and longer clinical life-span.

Structural and antioxidant analysis of Tartary buckwheat (Fagopyrum tartaricum Gaertn.) 13S globulin.

The main component of buckwheat seed storage proteins is 13S globulin. In this study, Tartary buckwheat 13S globulin was separated and its structural features were investigated using Edman sequencing and matrix-assisted laser desorption / ionization time of flight mass spectrometry (MALDI-TOF-MS). The protective effect of its enzymatic hydrolysates against oxidative stress induced by H2 O2 was also evaluated to elucidate the antioxidant mechanism. Results showed that the isolated Tartary buckwheat 13S globulin contained one acidic and one basic subunit, which were linked by a disulfide bond. Six Tartary buckwheat active peptides were obtained from the enzymatic hydrolysates of Tartary buckwheat 13S globulin acidic subunit with a molecular weight of 38 kDa, namely Pep-1, Pep-2, Pep-3, Pep-4, Pep-5, and Pep-6. Pre-treatment of cells with Tartary buckwheat active peptides maintained the redox state balance of HepG2 cells and protected the activity of antioxidant enzymes in HepG2 cells. The Tartary buckwheat active peptides improved oxidative stress in HepG2 cells via the PPAR-α/HO-1 pathway. These results provide an insight into the antioxidant mechanism of Tartary buckwheat 13S globulin and suggest that Tartary buckwheat active peptides can be used as a functional ingredient in the food industry. © 2019 Society of Chemical Industry.

Effects of arsenic exposure on D-serine metabolism in the hippocampus of offspring mice at different developmental stages.

The main purpose of this study was to verify the hypothesis that cognitive dysfunctions induced by arsenic exposure were related to the changes of D-serine metabolism in the hippocampus of offspring mice. Mother mice and their offsprings were exposed to 0, 15, 30 or 60mg/L sodium arsenite (NaAsO2) through drinking water from the first day of gestation until the end of lactation. D-serine levels in the hippocampus of mice of postnatal day (PND) 10, 20 and 40 were examined by high-performance liquid chromatography. Expressions of serine racemase (SR), D-amino acid oxidase (DAAO), alanine-serine-cysteine transporter-1 (asc-1) and subunits of N-methyl-D-aspartate receptors (NMDARs) in the hippocampus of mice were measured by Western blot and Real-time RT-PCR. Results showed that arsenic exposure significantly decreased D-serine levels of mice exposed to 60mg/L NaAsO2. Exposure to 60mg/L NaAsO2 could inhibit both mRNA and protein expression of SR, whereas increase in the protein expression of DAAO, only enhances the mRNA levels of DAAO of PND 20 mice. In addition, arsenic exposure could upregulate protein expression of asc-1. The mRNA and protein levels of NR1, NR2A and NR2B in the hippocampus of mice were down-regulated by arsenic. Findings from this study suggested that SR might play an important role in the reduction of D-serine levels caused by arsenic exposure, which might further influence the levels of NMDAR subunits especially on PND20, and then might disturb the function of NMDARs and cause the deficits of learning and memory ability of offspring mice.

Gram-Scale Solution-Phase Synthesis of Heptapeptide Side Chain of Teixobactin

We report herein a scalable synthesis of linear heptapeptide side chain of the depsipeptide natural product teixobactin through solution phase. The synthesis of heptapeptide was achieved through an efficient coupling of suitably protected tripeptide and tetrapeptide comprising of three d-amino acids and four usual l-amino acid subunits.

Potential of Molecular Weight and Structure of Tannins to Reduce Methane Emissions from Ruminants: A Review.

Simple SummaryRegardless of the production system adopted, ruminant livestock contribute to greenhouse emissions that are associated with climate change. Among the greenhouse gases, enteric methane produced from the rumen is of the greatest concern because it is the largest single source of livestock emissions. Among the different dietary strategies examined to decrease methanogenesis in ruminants, the use of tannins shows promise, but has received only moderate attention. However, tannins are abundant in both tropical and temperate plants and so are widely available globally and may be an economical approach for livestock producers to mitigate enteric methane emissions. This review explores the challenges and opportunities of using dietary tannins to reduce enteric methane emissions from ruminants.There is a need to reduce enteric methane (CH4) to ensure the environmental sustainability of ruminant production systems. Tannins are naturally found in both tropical and temperate plants, and have been shown to consistently decrease urinary nitrogen (N) excretion when consumed by ruminants. However, the limited number of in vivo studies conducted indicates that the effects of tannins on intake, digestibility, rumen fermentation, CH4 production and animal performance vary depending on source, type, dose, and molecular weight (MW). There are two main types of tannin in terrestrial plants: condensed tannin (CT; high MW) and hydrolysable tannin (HT; low MW). Consumption of CT and HT by ruminants can reduce N excretion without negatively affecting animal performance. High MW tannins bind to dietary protein, while low MW tannins affect rumen microbes, and thus, irrespective of type of tannin, N excretion is affected. The structure of high MW tannin is more diverse compared with that of low MW tannin, which may partly explain the inconsistent effects of CT on CH4 production reported in in vivo studies. In contrast, the limited number of in vivo studies with low MW HT potentially shows a consistent decrease in CH4 production, possibly attributed to the gallic acid subunit. Further in vivo studies are needed to determine the effects of tannins, characterized by MW and structural composition, on reducing CH4 emissions and improving animal performance in ruminants.

Microbial Metabolic Capacity for Intestinal Folate Production and Modulation of Host Folate Receptors.

Microbial metabolites, including B complex vitamins contribute to diverse aspects of human health. Folate, or vitamin B9, refers to a broad category of biomolecules that include pterin, para-aminobenzoic acid (pABA), and glutamate subunits. Folates are required for DNA synthesis and epigenetic regulation. In addition to dietary nutrients, the gut microbiota has been recognized as a source of B complex vitamins, including folate. This study evaluated the predicted folate synthesis capabilities in the genomes of human commensal microbes identified in the Human Microbiome Project and folate production by representative strains of six human intestinal bacterial phyla. Bacterial folate synthesis genes were ubiquitous across 512 gastrointestinal reference genomes with 13% of the genomes containing all genes required for complete de novo folate synthesis. An additional 39% of the genomes had the genetic capacity to synthesize folates in the presence of pABA, an upstream intermediate that can be obtained through diet or from other intestinal microbes. Bacterial folate synthesis was assessed during exponential and stationary phase growth through the evaluation of expression of select folate synthesis genes, quantification of total folate production, and analysis of folate polyglutamylation. Increased expression of key folate synthesis genes was apparent in exponential phase, and increased folate polyglutamylation occurred during late stationary phase. Of the folate producers, we focused on the commensal Lactobacillus reuteri to examine host–microbe interactions in relation to folate and examined folate receptors in the physiologically relevant human enteroid model. RNAseq data revealed segment-specific folate receptor distribution. Treatment of human colonoid monolayers with conditioned media (CM) from wild-type L. reuteri did not influence the expression of key folate transporters proton-coupled folate transporter (PCFT) or reduced folate carrier (RFC). However, CM from L. reuteri containing a site-specific inactivation of the folC gene, which prevents the bacteria from synthesizing a polyglutamate tail on folate, significantly upregulated RFC expression. No effects were observed using L. reuteri with a site inactivation of folC2, which results in no folate production. This work sheds light on the contributions of microbial folate to overall folate status and mammalian host metabolism.

Allergenicity reduction and rheology property of Lactobacillus-fermented soymilk.

This study aimed to investigate the reduction in the potential allergenicity of soymilk, and its rheological properties, after fermentation with Lactobacillus. Soymilk (SM) was fermented with Lactobacillus brevis and Lactobacillus sp. The molecular weight of fermented soymilk (FSM) was characterized using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and the potential allergenicity of FSM was analyzed using enzyme-linked immunosorbent assay in vitro and the BALB/c mouse model to detect changes in histamine, mouse mast cell protease-1 (mMCP-1), allergen-specific IgG/IgE, and cytokine levels and histomorphology of jejunum in vivo. The SDS-PAGE and enzyme linked immunosorbent assay (ELISA) showed that allergens of soybean (β-conglycinin and acidic subunit of glycinin) were almost degraded, and their immunoreactivity was decreased. In the BALB/c mouse model, the FSM group did not show anaphylactic shock symptoms compared with the SM group. Moreover, a tendency toward decreased serum allergen-specific IgG/IgE levels, plasma histamine levels, and mMCP-1 concentrations was observed in the FSM group. Furthermore, Th2-related cytokines were decreased, while IFN-γ production increased in spleen cell cultures. The intestinal villus was slightly damaged after the challenge. All these findings indicated that the Th1/Th2 balance in the FSM group shifted toward a Th1 response, ultimately reducing the potential allergenicity of FSM. Rheological assessment suggested that FSM has good viscous and pseudoplastic properties. Fermentation might be a promising method for producing tasty, hypoallergenic soybean products. © 2019 Society of Chemical Industry.

Contraception counseling for women with premenstrual dysphoric disorder (PMDD): current perspectives.

Premenstrual Dysphoric Disorder (PMDD) is a severe form of premenstrual syndrome (PMS) affecting up to 7% of reproductive age women. Women with PMDD are of reproductive age; therefore, contraception and treatment of PMDD are important considerations. The disorder as described in the DSM-V is characterized by moderate to severe psychological, behavioral and physical symptoms beginning up to two weeks prior to menses, resolving soon after the onset of menstruation and significantly interfering with daily functioning. PMDD develops in predisposed individuals after they are exposed to progesterone at the time of ovulation. It has been hypothesized that PMDD is in part attributable to luteal phase abnormalities in serotonergic activity and to altered configuration of ℽ-aminobutyric acid subunit A (GABAA) receptors in the brain triggered by the exposure to the neuroactive steroid progesterone metabolite, allopregnanolone (Allo). A large body of evidence suggests that selective serotonin reuptake inhibitors (SSRIs) can be effective in the treatment of PMDD. Combined hormonal contraceptive (CHC) pills, specifically the 20 mcg ethinyl estradiol/3mg drospirenone in a 24/4 extended cycle regimen has been shown to significantly improve the emotional and physical symptoms of PMDD. Other combined monophasic, extended cycle hormonal contraceptive pills with less androgenic progestins may also be helpful, although not well studied. Copper intrauterine devices (IUDs) are recommended for those not seeking hormonal contraceptives. Progestin-only methods including the progestin-only pill (POP), levonorgestrel (LNG) IUD, etonorgestrel implant or depot medroxyprogesterone acetate (DMPA) have the potential to negatively affect mood symptoms for women with or without baseline mood disorders, including PMDD. Careful counseling and close follow-up is recommended for patients with PMDD seeking these contraceptive methods.

Palladium(II)-Mediated Assembly of a M2L2 Macrocycle and M3L6 Cage from a Cyclopeptide-Derived Ligand.

A cyclic tetrapeptide L comprising two l-proline and two 3-amino-5-(pyridin-4-yl)benzoic acid subunits assembles into a dimetallic metallamacrocycle Pd2L2 and a trimetallic coordination cage Pd3L6 in the presence of suitable palladium(II) precursors. Pd2L2 recognizes organic anions in aqueous media, forming a particularly stable complex with sodium 2,6-naphthalenedisulfonate, in which two dianionic guest molecules reside in the cavity surrounded by the cyclopeptide ligands.

Interaction between plant phenolics and rice protein improved oxidative stabilities of emulsion

The interaction between rice protein isolate (RPI) and ferulic acid (FA) was systematically investigated. The results showed that fluorescence intensity of the RPI decreased gradually upon increasing the concentration of ferulic acid, and the maximum emission shifted from 352.0 to 359.2 nm. It was proposed that a static quenching of RPI-FA complex occurred, due to the hydrophobic interactions. Moreover, CD spectra and FT-IR spectroscopy data suggested that the concentration of β-turn and α-helix decreased while those of random coil and β-sheet increased in RPI-FA complex. The decrease of intensity of the amide I band and amide II band in the RPI-FA complex implied a significant reduction of protein α-helical structure and the presence of non-polar hydrophobic interactions. In addition, SDS-PAGE results demonstrated that ferulic acid reacted with glutelin acidic subunits (34–37 KDa) as well as globulin (26 KDa), and ferulic acid might bind with aromatic amino acid residues of RPI. Furthermore, the RPI-FA complex exhibited high DPPH• scavenging ability, ABTS+• scavenging ability and ORAC value. Finally, emulsion stabilized by RPI-FA complex could decrease the concentration of hydroperoxide, TBARS, and hexanal, thereby effectively restraining fat oxidation degradation.

Expression of recombinant transglutaminase gene in Pichia pastoris and its uses in restructured meat products

Transglutaminase is an effective enzyme that catalyzes the crosslinking of various meats, improves meat product quality, and is widely used in the meat industry. In this study, microbial transglutaminase (MTG) was expressed successfully in Pichia pastoris strain GS115, and the enzyme activity was approximately 0.70 U/ml. The recombinant MTG expressed in P. pastoris was used in the investigation of restructured pork and crosslinking of soy protein isolate (SPI) and chicken myofibrillar protein (MP). Results showed that the hardness, chewiness, and F1 of the restructured pork increased, and the adhesiveness decreased after MTG treatment, However, high temperature had greater effect on the texture of restructured pork after MTG treatment than that of the control. MTG can crosslink SPI component acidic subunits, subunits of β-conglycinin and MP component myosin heavy chain, and actin. MTG, as a food additive, can be successfully heterologously expressed, and the recombinant MTG has potential application in restructured meat products.

Molecular changes of phenolic-protein interactions in isolated proteins from flaxseed and soybean using Native-PAGE, SDS-PAGE, RP-HPLC, and ESI-MS analysis.

The effects of protein-phenolic interactions on the molecular characteristics of soybean and flaxseed proteins were investigated. Proteins were isolated from soybean and flaxseed using isoelectric precipitation, followed by extraction of free and bound phenolics. The effects of elimination of the phenolic compounds on molecular characteristics of the protein isolates were studied using reversed phase-high performance liquid chromatography (RP-HPLC), Native and sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) and electron spray ionization-mass spectrometry (ESI-MS). The Native-PAGE fractions from isolated proteins from full-fat flaxseed and soybean revealed that protein migration was affected by removal of bound phenolics. SDS-PAGE from full-fat and defatted protein isolates of flaxseed and soybean revealed that the removal of bound phenolics affected the molecular characteristics of protein subunits. Soybean protein isolates had protein-phenolic interactions through acidic and basic subunits. RP-HPLC and ESI-MS showed that the removal of bound and free phenolics had only minor effects on the molecular characteristics of isolated proteins from defatted and full-fat soybean. With respect to isolated proteins from flaxseed, the removal of bound phenolics showed little effect on the electrophoretic behavior of the proteins or the protein subunits. PRACTICAL APPLICATIONS: Phenolic-protein and phenolic-lipid-protein interactions may affect the nutritional, physicochemical, and functional properties of isolated proteins from food in flaxseed and soybean.