Effects of Baicalein and Chrysin on the Structure and Functional Properties of β-Lactoglobulin

Two flavonoids with similar structures, baicalein (Bai) and chrysin (Chr), were selected to investigate the interactions with β-lactoglobulin (BLG) and the influences on the structure and functional properties of BLG by multispectral methods combined with molecular docking and dynamic (MD) simulation techniques. The results of fluorescence quenching suggested that both Bai and Chr interacted with BLG to form complexes with the binding constant of the magnitude of 105 L·mol−1. The binding affinity between BLG and Bai was stronger than that of Chr due to more hydrogen bond formation in Bai–BLG binding. The existence of Bai or Chr induced a looser conformation of BLG, but Chr had a greater effect on the secondary structure of BLG. The surface hydrophobicity and free sulfhydryl group content of BLG lessened due to the presence of the two flavonoids. Molecular docking was performed at the binding site of Bai or Chr located in the surface of BLG, and hydrophobic interaction and hydrogen bond actuated the formation of the Bai/Chr–BLG complex. Molecular dynamics simulation verified that the combination of Chr and BLG decreased the stability of BLG, while Bai had little effect on it. Moreover, the foaming properties of BLG got better in the presence of the two flavonoids compounds and Bai improved its emulsification stability of the protein, but Chr had the opposite effect. This work provides a new idea for the development of novel dietary supplements using functional proteins as flavonoid delivery vectors.

Influence of the Mixture of Carrageenan Oligosaccharides and Egg White Protein on the Gelation Properties of Culter alburnus Myofibrillar Protein under Repeated Freezing–Thawing Cycles

This study aims to investigate the influence of the mixture (CGO/EWP) of carrageenan oligosaccharide (CGO) and egg white protein (EWP) (CGO/EWP, CGO: EWP = 1:1, m/m) on the functional, structural, and gelling properties of Culter alburnus myofibrillar protein (MP) during repeated freezing–thawing cycles by treating MP samples separately with EWP, CGO, or CGO/EWP based on the wet weight (1%, m/m), using samples without any cryoprotectant as the blank group. After the second repeated freezing–thawing cycle, the sulfhydryl group content was found to be significantly (p < 0.05) higher in the CGO/EWP (30.57 nmol/mg) and CGO (36.14 nmol/mg) groups than in the EWP group (23.80 nmol/mg), indicating that CGO/EWP and CGO can more effectively delay the oxidative deterioration of functional groups. Additionally, the surface hydrophobicity was shown to be significantly lower in the CGO (25.74) and CGO/EWP (27.46) groups than in the EWP (34.66) and blank (39.32) groups. Moreover, the α-helix content was higher in the CGO (35.2%) and CGO/EWP (32.3%) groups than in the EWP (29.2%) and blank (25.0%) groups. These data indicated that CGO and CGO/EWP could more effectively increase the structural stability, thereby inhibiting the exposure of hydrophobic groups and curbing the decline of α-helix content. During the heat-induced gel-forming process, EWP and CGO/EWP could enhance the gel viscoelasticity and strength. After the second freezing–thawing cycle, when compared with the blank group, the CGO/EWP group showed significantly (p < 0.05) higher water-holding capacity (66.30% versus 53.93%) and shorter T22 relaxation time (413.56 versus 474.99 ms). The integrated results indicated that CGO/EWP could more effectively delay the decrease of protein–water molecular interaction forces in the MP gel. This study shed light on the mechanism of CGO/EWP as a cryoprotective mixture in improving the deterioration of MP gelation properties during repeated freezing–thawing cycles.

Influence of Angiotensin-Converting Enzyme Inhibitors (ACEi) on Angiogenesis Induced by Physical Exercise

Angiotensin-converting enzyme inhibitors (ACEi) are used to reduce blood pressure and vascular resistance by modulating the ACE activity responsible for the angiotensin II formation. However, different ACEi seem to influence exercise-induced angiogenesis. The objective of this review was to investigate the effects of different ACEi on vessel growth in skeletal muscle induced by exercise training. The present study is characterized by a narrative literature review design, the databases of Scielo, Google Scholar and PubMed were consulted. There are different groups of ACEi , sulfhydryl group such as captopril and a carboxyl group such as perindiporil and enalapril that can influence their effects on ACE activity. It is already known that exercise promotes the increase of vessels from vessels already existing in the skeletal musculature, a process known as angiogenesis and contributes to the blood pressure reduction (BP). Although these different responses are still scarce, vessel endothelial growth factor (VEFG) and nitric oxide (NO) may participate. Thus, the use of different ACEi can influences the angiogenesis responses induced by exercise, being one of the important mechanisms for BP reduction. The choice of ACEi group should be carefully analyzed for hypertensive individuals who practice physical exercise. Keywords: Physical Education and Training. Microcirculation. Hypertension. ResumoOs inibidores da enzima conversora de angiotensina (iECA) são utilizados para redução da pressão arterial e resistência vascular modulando a atividade da ECA responsável pela formação da angiotensina II. Entretanto, diferentes iECAs parecem influenciar a angiogênese induzida pelo exercício físico. Desta maneira objetivo desta revisão foi investigar os efeitos de diferentes iECA sobre o crescimento de vasos no musculo esquelético induzido pelo exercício físico. O presente estudo caracteriza-se um delineamento de revisão de literatura narrativa, foram consultadas as bases de dados do Scielo, Google acadêmico e PubMed. Existem grupos distintos dos iECAs, grupo sulfidrila como o captopril e o grupo carboxila como o perindiporil e grupo que pode influenciar seus efeitos sobre a atividade da ECA. Já é sabido que O exrcício promove o aumento de vasos a partir de vasos já existentes na musculatura esquelética, processo conhecido como angiogênese e colabora para redução da pressão arterial (PA). Entretanto os iECAs parecem influenciar esta resposta do aumento da densidade capilar no músculo esquelético. Embora ainda sejam escassos estas diferentes respostas podem ter as participações do fator de crescimento endotelial de vasos (VEFG) e o óxido nítrico (NO). Desta maneira o uso dos grupos do iECAs podem influenciar as resposta da angiogênese induzido pelo exercício sendo um dos mecanismos importantes pela redução da PA. A escolha do grupo de iECA deve ser analisada com cautela para indivíduoS hipertensos que praticam exercício físico. Palavras-chave: Educação Física e Treinamento. Microcirculação. Hipertensão

Effects of three treatments on protein structure and gel properties of Perccottus glenii myofibrillar protein

In order to improve Perccottus glenii myofibrillar protein (MP) gel properties, three treatments were evaluated: ultrasonic, transglutaminase (TGase) and combined ultrasonic-transglutaminase treatments. Combined ultrasonic-transglutaminase treatment altered protein structure and gel properties most dramatically. As compared with untreated control group protein, treated protein gels possessed decreased sulfhydryl group content and increases in water holding capacity, whiteness value and hydrophobic interactions that increased gel strength value by up to 3.79 times that of untreated protein gel. Protein structural and Differential scanning calorimetry (DSC) analyses revealed that combined ultrasonic-TGase treatment increased both protein thermal denaturation temperature and UV absorbance (as compared to control and other treatment groups) that supported formation of MP gels with desirable characteristics. These results provide a theoretical basis for development of superior MP gels to promote greater utilization of this fish protein resource by the food industry.

Carry-Over Effects of Desiccation Stress on the Oxidative Status of Fasting Anuran Juveniles

Amphibians are sensitive to deteriorating environmental conditions, especially during transition to a terrestrial environment which is full of uncertainties. Harsh conditions, such as desiccation during earlier stages, affect different larval traits with possible carry-over effects on juvenile and adult life histories. The first consequences of the effects can be seen in juveniles in the challenges to find food and the ability to survive without it in a terrestrial habitat. Body size and the internal energy reserves acquired during the larval phase play an important role in this period. Herein, we tested how different water regimes (low water availability, desiccation and constant high-water availability) during larval development reflect on the oxidative status and ability of yellow belly toad (Bombina variegata) juveniles to endure short-term fasting. The desiccation regime significantly reduced the body size of metamorphs. The same was observed after 2 weeks of fasting, while the feeding treatment reduced differences mostly in the body mass of individuals from different water regimes. This was the result of a greater gain in mass in juveniles pre-exposed to desiccation. Pre-exposure to desiccation also modified the parameters of the antioxidant system (AOS) under feeding conditions, leading to higher values of superoxide dismutase, glutathione reductase and glutathione S-transferase, glutathione and sulfhydryl group concentrations, and lower glutathione peroxidase in comparison to juveniles reared under constant water. The increase in the AOS of juveniles can be considered as a physiological carry-over effect of desiccation, probably as the result of compensatory growth and/or earlier exposure to chronic stress. However, water levels during larval development did not exert significant effects on the oxidative status of juveniles subjected to food unavailability. Fasting juveniles, both control and desiccated, were exposed to oxidative stress, significantly higher lipid peroxide concentrations, lower superoxide dismutase, glutathione peroxidase, glutathione S-transferase, glutathione and sulfhydryl group values in comparison to feeding individuals. The lack of food in juvenile anurans activated the AOS response in the same manner, regardless of body size and stress pre-exposure, suggesting that the generally accepted hypothesis about the influence of metamorphic body size on the fitness of the postmetamorphic stage should be tested further.

Spatiotemporal Protein Expression Profiles of QSOX1 in the Murine Uterus, Placenta, and Embryo during Pregnancy

Quiescin Q6 sulfhydryl oxidase 1 (QSOX1) catalyzes the oxidation of the sulfhydryl group to disulfide bond and is widely expressed in various tissues. This study focuses on investigating QSOX1′s spatiotemporal and cellular protein expression profile of the pregnant uterus, placenta, and developing embryo during mouse pregnancy. Immunohistochemical staining was used to reveal the localization of QSOX1 protein, and HistoQuest was applied to quantify protein levels. The expression level of QSOX1 in the decidua and muscle cells of the pregnant uterus fluctuated dramatically during pregnancy. QSOX1 was ubiquitously expressed in the labyrinth, junction zone, and chorionic plate in the placenta. The quantitative analysis found that this protein was highly expressed in the spinal cord, lens, midbrain, cerebellum, medulla oblongata, and tooth of mouse embryos, followed by the heart, intercostal muscle, diaphragm, intermediate zone, extrinsic ocular muscle, spine, pons, epidermis, tongue, ganglion, vomeronasal organ, thoracic vertebrae, and thymus. Interestingly, QSOX1 was also markedly expressed in olfactory system tissues. This comprehensive spatiotemporal study of QSOX1 protein expression will provide a basis for further investigations of the QSOX1 physiological function in the pregnant uterus, placenta, and developing embryo.

A Novel Glutathione S-Transferase Gtt2 Class (VpGSTT2) Is Found in the Genome of the AHPND/EMS Vibrio parahaemolyticus Shrimp Pathogen

Glutathione S-transferases are a family of detoxifying enzymes that catalyze the conjugation of reduced glutathione (GSH) with different xenobiotic compounds using either Ser, Tyr, or Cys as a primary catalytic residue. We identified a novel GST in the genome of the shrimp pathogen V. parahaemolyticus FIM- S1708+, a bacterial strain associated with Acute Hepatopancreatic Necrosis Disease (AHPND)/Early Mortality Syndrome (EMS) in cultured shrimp. This new GST class was named Gtt2. It has an atypical catalytic mechanism in which a water molecule instead of Ser, Tyr, or Cys activates the sulfhydryl group of GSH. The biochemical properties of Gtt2 from Vibrio parahaemolyticus (VpGSTT2) were characterized using kinetic and crystallographic methods. Recombinant VpGSTT2 was enzymatically active using GSH and CDNB as substrates, with a specific activity of 5.7 units/mg. Low affinity for substrates was demonstrated using both Michaelis–Menten kinetics and isothermal titration calorimetry. The crystal structure showed a canonical two-domain structure comprising a glutathione binding G-domain and a hydrophobic ligand H domain. A water molecule was hydrogen-bonded to residues Thr9 and Ser 11, as reported for the yeast Gtt2, suggesting a primary role in the reaction. Molecular docking showed that GSH could bind at the G-site in the vicinity of Ser11. G-site mutationsT9A and S11A were analyzed. S11A retained 30% activity, while T9A/S11A showed no detectable activity. VpGSTT2 was the first bacterial Gtt2 characterized, in which residues Ser11 and Thr9 coordinated a water molecule as part of a catalytic mechanism that was characteristic of yeast GTT2. The GTT2 family has been shown to provide protection against metal toxicity; in some cases, excess heavy metals appear in shrimp ponds presenting AHPND/EMS. Further studies may address whether GTT2 in V. parahaemolyticus pathogenic strains may provide a competitive advantage as a novel detoxification mechanism.

Antioxidant Mechanism of Yam Saponin, Hesperidin, Ginger Extract on Oxidative Chicken Myofibrillar Protein

The antioxidant mechanism of three plant extracts on the oxidative myofibrillar proteins oxidized by Fe3+/H2O2 at 0 °C for 12 h was analyzed. These plant extracts were added to myofibrillar proteins with the concentrations of 0.5 and 1 mg/mL Besides, the group without added extracts was adopted as controls. Total sulfhydryl content, carbonyls, surface hydrophobicity, and protein cross-linking, protein gel properties were analyzed. In the meantime, the oxidized suspensions were processed as protein gels. Then, the water-holding capacity and the hardness of gels were analyzed. The resulted showed that the suspensions of three plant extracts and the oxidized myofibrillar proteins led to a significant decrease in surface hydrophobicity, carbonyls and gel hardness of the sulfhydryl group, while three plant extracts promoted aggregation of the myofibrillar proteins and increased water-holding capacity of gels compared with that of the control. The scanning electron microscope showed that the gels structure of the three extracts were obviously better than that of the control group, and the ginger group was the best.Yam saponin exhibited the best antioxidant effect, followed by ginger extract and hesperidin.

Caerulomycin and collismycin antibiotics share a trans-acting flavoprotein-dependent assembly line for 2,2’-bipyridine formation

Linear nonribosomal peptide synthetases (NRPSs) and polyketide synthases (PKSs) template the modular biosynthesis of numerous nonribosomal peptides, polyketides and their hybrids through assembly line chemistry. This chemistry can be complex and highly varied, and thus challenges our understanding in NRPS and PKS-programmed, diverse biosynthetic processes using amino acid and carboxylate building blocks. Here, we report that caerulomycin and collismycin peptide-polyketide hybrid antibiotics share an assembly line that involves unusual NRPS activity to engage a trans-acting flavoprotein in C-C bond formation and heterocyclization during 2,2’-bipyridine formation. Simultaneously, this assembly line provides dethiolated and thiolated 2,2’-bipyridine intermediates through differential treatment of the sulfhydryl group arising from l-cysteine incorporation. Subsequent l-leucine extension, which does not contribute any atoms to either caerulomycins or collismycins, plays a key role in sulfur fate determination by selectively advancing one of the two 2,2’-bipyridine intermediates down a path to the final products with or without sulfur decoration. These findings further the appreciation of assembly line chemistry and will facilitate the development of related molecules using synthetic biology approaches.

A Case of Autoimmune Hypoglycemia (Insulin Autoimmune Syndrome)

Introduction: Insulin Autoimmune Syndrome (IAS) is a condition caused by Insulin Autoantibody (IAA). IAS was initially reported in 1970 by Yukimasa Hirata from Japan. From 1970 to 2009, 380 cases were reported worldwide. We report a case of IAS in an African-American man who had recurrent episodes of syncope secondary to hypoglycemia. Case Report: A 50-year-old African American man with hypertension presented to emergency room after syncope. His initial blood glucose (BG) was 27 mg/dl. After Dextrose and glucagon injection, BG became 270 and he regained consciousness without any deficit. Vital signs and physical examination were unremarkable. He was not on any medication, and had no access to insulin or oral hypoglycemic agents. No family history of endocrine disorders, malignancy or autoimmune diseases were reported. He had been hospitalized two times for syncope secondary to hypoglycemia. During hospitalization, fasting insulin level was &gt;1000 IU/ml with high C-peptide (3.5ng/ml). Hypoglycemic agents assay was negative. During outpatient follow-ups, fasting labs showed C-peptide 1.59 ng/ml, Insulin antibody 37.6 U/ml while venous BG was 65 mg/dl. Random BG at different occasions were 65, 68 and 55 mg/dl. HbA1C was normal. BMI was gradually increased from 32.4 to 34.8 in 6 months. During the third hospitalization, fasting venous BG were 45 and 57 on two different days, Insulin was 2111 IU/ml and C-Peptide was 1.78 ng/ml. Other labs including cortisol and TSH were normal. CT abdomen was unremarkable. Discussion: In IAS, Insulin secreted after meal is bound by IAA. It causes hyperglycemia unchecked which triggers further insulin secretion. When the bound insulin dissociates from antibodies, it causes significant hyperinsulinemia and subsequent hypoglycemia. IAS can occur regardless of previous insulin exposure, as a solitary autoimmune manifestation or in association with other autoimmune disorders. It can be induced by drugs that contain sulfhydryl group. Etiology of IAS is still not fully understood but there are theories that genetic predisposition such as class II Human Leukocyte Antigen (HLA) and environmental triggers such as medications, viruses, hematological diseases etc. might play a role. In our patient, failure to test IAA in past admissions and lack of continuity of care delayed the diagnosis. Conclusion: IAS should be considered especially in those who have no clear etiology of hypoglycemia in order to avoid unnecessary diagnostic and therapeutic procedures. Gold standard test for definitive diagnosis is IAA. As IAS is frequently self-remitting, supportive management is usually recommended. In severe cases, pharmacotherapies that reduce insulin secretion and immunosuppressants are occasionally necessary. But there is still no study that compares different treatment measures.