Causative Links between Protein Aggregation and Oxidative Stress: A Review.

Compelling evidence supports a tight link between oxidative stress and protein aggregation processes, which are noticeably involved in the development of proteinopathies, such as Alzheimer's disease, Parkinson's disease, and prion disease. The literature is tremendously rich in studies that establish a functional link between both processes, revealing that oxidative stress can be either causative, or consecutive, to protein aggregation. Because oxidative stress monitoring is highly challenging and may often lead to artefactual results, cutting-edge technical tools have been developed recently in the redox field, improving the ability to measure oxidative perturbations in biological systems. This review aims at providing an update of the previously known functional links between oxidative stress and protein aggregation, thereby revisiting the long-established relationship between both processes.

Transcriptional regulation of FeS biogenesis genes: A possible shield against arsenate toxicity activated by Yap1.

In the eukaryotic model yeast Saccharomyces cerevisiae, arsenic (As) detoxification is regulated by two transcriptional factors, Yap8 and Yap1. Yap8 specifically controls As extrusion from the cell, whether Yap1 avoids arsenic-induced oxidative damages. Accordingly, cells lacking both Yap1 and Yap8 are more sensitive to arsenate than cells lacking each regulator individually. Strikingly enough, the same sensitivity pattern was observed under anoxia, suggesting that Yap1 role in As detoxification might not be restricted to the regulation of the oxidative stress response. This finding prompted us to study the transcriptomic profile of wild-type and yap1 mutant cells exposed to arsenate. Interestingly, we found that, under such conditions, several genes involved in the biogenesis of FeS proteins were upregulated in a Yap1-dependent way. In line with this observation, arsenate treatment decreases the activity of the mitochondrial aconitase, Aco1, an FeS cluster-containing enzyme, this effect being even more pronounced in the yap1 mutant. Reinforcing the relevance of FeS cluster biogenesis in arsenate detoxification, the overexpression of several ISC and CIA machinery genes alleviates the deleterious effect of arsenate caused by the absence of Yap1 and Yap8. Altogether our data suggest that the upregulation of FeS biogenesis genes regulated by Yap1 might work as a cellular shield against arsenate toxicity.

Iron-sulfur protein odyssey: exploring their cluster functional versatility and challenging identification.

Iron-sulfur (Fe-S) clusters are an essential and ubiquitous class of protein-bound prosthetic centers that are involved in a broad range of biological processes (e.g. respiration, photosynthesis, DNA replication and repair and gene regulation) performing a wide range of functions including electron transfer, enzyme catalysis, and sensing. In a general manner, Fe-S clusters can gain or lose electrons through redox reactions, and are highly sensitive to oxidation, notably by small molecules such as oxygen and nitric oxide. The [2Fe-2S] and [4Fe-4S] clusters, the most common Fe-S cofactors, are typically coordinated by four amino acid side chains from the protein, usually cysteine thiolates, but other residues (e.g. histidine, aspartic acid) can also be found. While diversity in cluster coordination ensures the functional variety of the Fe-S clusters, the lack of conserved motifs makes new Fe-S protein identification challenging especially when the Fe-S cluster is also shared between two proteins as observed in several dimeric transcriptional regulators and in the mitoribosome. Thanks to the recent development of in cellulo, in vitro, and in silico approaches, new Fe-S proteins are still regularly identified, highlighting the functional diversity of this class of proteins. In this review, we will present three main functions of the Fe-S clusters and explain the difficulties encountered to identify Fe-S proteins and methods that have been employed to overcome these issues.

Regulations of mitoNEET by the key redox homeostasis molecule glutathione.

Human mitoNEET (mNT) and CISD2 are two NEET proteins characterized by an atypical [2Fe-2S] cluster coordination involving three cysteines and one histidine. They act as redox switches with an active state linked to the oxidation of their cluster. In the present study, we show that reduced glutathione but also free thiol-containing molecules such as ß-mercaptoethanol can induce a loss of the mNT cluster under aerobic conditions, while CISD2 cluster appears more resistant. This disassembly occurs through a radical-based mechanism as previously observed with the bacterial SoxR. Interestingly, adding cysteine prevents glutathione-induced cluster loss. At low pH, glutathione can bind mNT in the vicinity of the cluster. These results suggest a potential new regulation mechanism of mNT activity by glutathione, an essential actor of the intracellular redox state.

Safety evaluation of the food enzyme rennet containing chymosin and pepsin A from the abomasum of suckling calves, goats, lambs and buffaloes.

The food enzyme containing chymosin (EC 3.4.23.4) and pepsin (EC 3.4.23.1) is prepared from the abomasum of suckling calves, goats, lambs and buffaloes by Caglificio Clerici S.p.A. It is intended to be used in the production of cheese. As no concerns arise from the source of the food enzyme, from its manufacture and based on the history of safe use and consumption, the Panel considered that toxicological data were not required and no exposure assessment was necessary. The similarity of the amino acid sequences of the two proteins (chymosin and pepsin A) to those of known allergens was searched and two matches were found with respiratory allergens. The Panel considered that the risk of allergic reactions by dietary exposure cannot be excluded, but the likelihood is low. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.

Safety evaluation of the food enzyme endo-1,4-ß-xylanase from the genetically modified Bacillus velezensis strain AR-112.

The food enzyme endo-1,4-ß-xylanase (4-ß-d-xylan xylanohydrolase, EC 3.2.1.8) is produced with the genetically modified Bacillus velezensis strain AR-112 by AB Enzymes GmbH. The genetic modifications do not give rise to safety concerns. The food enzyme is free from viable cells of the production organism and its DNA. It is intended to be used in baking processes. Dietary exposure to the food enzyme-total organic solids (TOS) was estimated to be up to 0.024 mg TOS/kg body weight (bw) per day in European populations. As the production strain B. velezensis strain AR-112 meets the requirements for the qualified presumption of safety (QPS) approach to safety assessment and no issue of concern arose from the production process, no toxicological data are required. A search for the similarity of the amino acid sequence of the food enzyme to known allergens was made and no match was found. The Panel considered that, under the intended conditions of use, the risk of allergic reactions upon dietary exposure cannot be excluded, but the likelihood is low. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.

Safety evaluation of the food enzyme glucan 1,4-α-maltohydrolase from the genetically modified Bacillus subtilis strain BABSC.

The food enzyme glucan 1,4-α-maltohydrolase (4-α-d-glucan α-maltohydrolase, EC 3.2.1.133) is produced with the genetically modified Bacillus subtilis strain BABSC by Advanced Enzyme Technologies Ltd. The requirements for the qualified presumption of safety (QPS) approach have not been met. The food enzyme is free from viable cells of the production organism and its DNA. It is intended to be used in baking processes and starch processing for the production of glucose syrups and other starch hydrolysates. Since residual amounts of total organic solids (TOS) are removed, dietary exposure was not calculated for starch processing for the production of glucose syrups and other starch hydrolysates. For baking processes, the dietary exposure was estimated to be up to 0.101 mg TOS/kg body weight per day in European populations. No toxicological studies were provided by the applicant. A search for the similarity of the amino acid sequence of the food enzyme to known allergens was made and one match with a respiratory allergen was found. The Panel considered that the risk of allergic reactions by dietary exposure cannot be excluded, but the likelihood is low. In the absence of appropriate data to fully characterise the production strain, the Panel was unable to conclude on the safety of the food enzyme under the intended conditions of use.

Safety evaluation of an extension of use of the food enzyme containing cellulase, endo-1,3(4)-ß-glucanase and endo-1,4-ß-xylanase from the non-genetically modified Trichoderma reesei strain AR-256.

The food enzyme containing cellulase (EC 3.2.1.4), endo-1,3(4)-ß-glucanase (EC 3.2.1.6) and endo-1,4-ß-xylanase (EC 3.2.1.8) is produced with the non-genetically modified Trichoderma reesei strain AR-256 by AB-Enzymes GmbH. A safety evaluation of this food enzyme was made previously, in which EFSA concluded that this food enzyme did not give rise to safety concerns when used in seven food manufacturing processes. Subsequently, the applicant requested to extend its use to include two additional processes. In this assessment, EFSA updated the safety evaluation of this food enzyme when used in a total of nine food manufacturing processes: processing of cereals and other grains for the production of 1) baked products, 2) cereal-based products other than baked, 3) brewed products, 4) starch and gluten fractions, 5) distilled alcohol; processing of fruits and vegetables for the production of 6) wine and wine vinegar, 7) juices, 8) fruit and vegetable products other than juices and 9) fruit-derived distilled alcoholic beverages other than from grape. As the food enzyme-total organic solids (TOS) is removed from or not carried into the final foods in three food manufacturing processes, the dietary exposure to the food enzyme-TOS was estimated only for the remaining six processes. It was up to 4.049 mg TOS/kg body weight (bw) per day in European populations. Using the no observed adverse effect level (NOAEL) reported in the previous opinion (939 mg TOS/kg bw per day), the Panel derived a revised margin of exposure of at least 232. Based on the revised exposure calculation and the outcome of the previous evaluation, the Panel concluded that this food enzyme does not give rise to safety concerns under the revised intended conditions of use.

Safety evaluation of the food enzyme phosphoinositide phospholipase C from the genetically modified Pseudomonas fluorescens strain PIC.

The food enzyme phosphoinositide phospholipase C (1-phosphatidyl-1D-myo-inositol-4,5-bisphosphate inositoltrisphosphohydrolase EC 3.1.4.11.) is produced with the genetically modified Pseudomonas fluorescens strain PIC by DSM Food specialties B.V. The genetic modifications do not give rise to safety concerns. The food enzyme is free from viable cells of the production organism and its DNA. It is intended to be used in the processing of fats and oils for the production of refined edible fats and oils by degumming. Since residual amounts of the total organic solids are removed by the washing and purification steps applied during degumming, dietary exposure estimation and toxicity testing were considered unnecessary. A search for the similarity of the amino acid sequence of the food enzyme to known allergens was made and no matches were found. The Panel considered that the risk of allergic reactions by dietary exposure cannot be excluded, but the likelihood for this to occur is low. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.

Safety evaluation of the food enzyme asparaginase from the genetically modified Aspergillus niger strain AGN.

The food enzyme asparaginase (l-asparagine amidohydrolase; EC 3.5.1.1) is produced with the genetically modified Aspergillus niger strain AGN by DSM Food Specialties B.V. The genetic modifications do not give rise to safety concerns. The food enzyme is free from viable cells of the production organism and its DNA. It is intended to be used to prevent acrylamide formation in food processing. The dietary exposure to the food enzyme-total organic solids (TOS) was estimated to be up to 1.434 mg TOS/kg body weight (bw) per day in European populations. The toxicity studies were carried out with an asparaginase from A. niger (strain ASP). The Panel considered this food enzyme as a suitable substitute for the asparaginase to be used in the toxicological studies, because the genetic differences between the production strains are not expected to result in a different toxigenic potential, and the raw materials and manufacturing processes of both food enzymes are comparable. Genotoxicity tests did not indicate a safety concern. The systemic toxicity was assessed by means of a repeated dose 90-day oral toxicity study in rats. The Panel identified a no observed adverse effect level of 1038 mg TOS/kg bw per day, which, when compared with the estimated dietary exposure, resulted in a margin of exposure of at least 724. A search for the similarity of the amino acid sequence of the food enzyme to known allergens was made and no match was found. The Panel considered that the risk of allergic reactions by dietary exposure cannot be excluded, but the likelihood is low. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.

Safety evaluation of an extension of use of the food enzyme α-l-rhamnosidase from the non-genetically modified Penicillium adametzii strain AE-HP.

The food enzyme α-l-rhamnosidase (α-l-rhamnoside rhamnohydrolase; EC 3.2.1.40) is produced with Penicillium adametzii strain AE-HP by Amano Enzymes Inc. A safety evaluation of this food enzyme was made previously, in which EFSA concluded that this food enzyme did not give rise to safety concerns when used in two food manufacturing processes. Subsequently, the applicant has requested to extend its use to include two additional processes. In this assessment, EFSA updated the safety evaluation of this food enzyme when used in a total of four food manufacturing processes. Dietary exposure to the food enzyme-total organic solids (TOS) was calculated to be up to 0.022 mg TOS/kg body weight (bw) per day in European populations. Using the no observed adverse effect level reported in the previous opinion (300 mg TOS/kg bw per day, the highest dose tested), the Panel derived a margin of exposure of at least 13,636. Based on the data provided for the previous evaluation and the revised margin of exposure in the present evaluation, the Panel concluded that this food enzyme does not give rise to safety concerns under the revised intended conditions of use.

Safety evaluation of an extension of use of the food enzyme glutaminase from the non-genetically modified Bacillus amyloliquefaciens strain AE-GT.

The food enzyme glutaminase (l-glutamine amidohydrolase; EC 3.5.1.2) is produced with the non-genetically modified Bacillus amyloliquefaciens strain AE-GT by Amano Enzyme Inc. A safety evaluation of this food enzyme was made previously, in which EFSA concluded that this food enzyme did not give rise to safety concerns when used in five food manufacturing processes. Subsequently, the applicant requested to extend its use to thirteen additional processes and to revise the use levels. In this assessment, EFSA updated the safety evaluation of this food enzyme when used in a total of eighteen food manufacturing processes. As the food enzyme-total organic solids (TOS) are removed from the final foods in two food manufacturing processes, the dietary exposure to the food enzyme-TOS was estimated only for the remaining sixteen processes. Dietary exposure was calculated to be up to 0.678 mg TOS/kg body weight per day in European populations. Based on the data provided for the previous evaluation and the revised dietary exposure in the present evaluation, the Panel concluded that this food enzyme does not give rise to safety concerns under the revised intended conditions of use.

Safety evaluation of an extension of use of the food enzyme α-amylase from the non-genetically modified Bacillus licheniformis strain AE-TA.

The food enzyme α-amylase (4-α-d-glucan glucanohydrolase; EC 3.2.1.1) is produced with the non-genetically modified microorganism Bacillus licheniformis strain AE-TA by Amano Enzyme Inc. A safety evaluation of this food enzyme was made previously, in which EFSA concluded that this food enzyme did not give rise to safety concerns when used in eight food manufacturing processes. Subsequently, the applicant has requested to extend its use to include one additional process and to revise the use levels. In this assessment, EFSA updated the safety evaluation of this food enzyme when used in a total of nine food manufacturing processes. As the food enzyme-total organic solids (TOS) are removed from the final foods in two food manufacturing processes, the dietary exposure to the food enzyme-TOS was estimated only for the remaining seven processes. Dietary exposure was calculated to be up to 0.382 mg TOS/kg body weight per day in European populations. Based on the data provided for the previous evaluation and the revised dietary exposure in the present evaluation, the Panel concluded that this food enzyme does not give rise to safety concerns under the revised intended conditions of use.

Safety evaluation of an extension of use of the food enzyme bacillolysin from the non-genetically modified Bacillus amyloliquefaciens strain AE-NP.

The food enzyme bacillolysin (EC 3.4.24.28) is produced with the non-genetically modified Bacillus amyloliquefaciens strain AE-NP by Amano Enzyme Inc. A safety evaluation of this food enzyme was made previously, in which EFSA concluded that this food enzyme did not give rise to safety concerns when used in thirteen food manufacturing processes. Subsequently, the applicant requested to extend its use to two additional processes. In this assessment, EFSA updated the safety evaluation of this food enzyme when used in a total of fifteen food manufacturing processes. As the food enzyme-total organic solids (TOS) are removed in two food manufacturing processes, the dietary exposure to the food enzyme-TOS was estimated only for the remaining thirteen processes. Dietary exposure was calculated to be up to 35.251 mg TOS/kg body weight per day in European populations. Based on the data provided for the previous evaluation and the revised dietary exposure in the present evaluation, the Panel concluded that this food enzyme does not give rise to safety concerns under the revised intended conditions of use.

Safety evaluation of an extension of use of the food enzyme 4-α-glucanotransferase from the non-genetically modified Aeribacillus pallidus strain AE-SAS.

The food enzyme 4-α-glucanotransferase (1,4-α-d-glucan:1,4-α-d-glucan 4-α-d-glycosyltransferase, EC 2.4.1.25) is produced with the non-genetically modified Aeribacillus pallidus strain AE-SAS by Amano Enzyme Inc. A safety evaluation of this food enzyme was made previously, in which EFSA concluded that this food enzyme did not give rise to safety concerns when used in two food manufacturing processes. Subsequently, the applicant requested to extend its use to two additional processes. In this assessment, EFSA updated the safety evaluation of this food enzyme for use in a total of four food manufacturing processes. As the food enzyme-total organic solids (TOS) is removed from the final foods in one food manufacturing process, the dietary exposure to the food enzyme-TOS was estimated only for the remaining three processes. Dietary exposure was up to 0.040 mg TOS/kg body weight (bw) per day in European populations. When combined with the no observed adverse effect level reported in the previous opinion (900 mg TOS/kg bw per day, the highest dose tested), the Panel derived a margin of exposure of at least 22,500. Based on the data provided for the previous evaluation and the revised margin of exposure, the Panel concluded that this food enzyme does not give rise to safety concerns under the revised intended conditions of use.

Safety evaluation of an extension of use of the food enzyme endo-polygalacturonase from the genetically modified Aspergillus oryzae strain AR-183.

The food enzyme endo-polygalacturonase ((1 → 4)-α-d-galacturonan glycanohydrolase EC 3.2.1.15) is produced with the genetically modified Aspergillus oryzae strain AR-183 by AB ENZYMES GmbH. A safety evaluation of this food enzyme was made previously, in which EFSA concluded that this food enzyme did not give rise to safety concerns when used in five food manufacturing processes. Subsequently, the applicant requested to extend its use to two additional processes. In this assessment, EFSA updated the safety evaluation of this food enzyme for use in a total of seven food manufacturing processes. As the food enzyme-total organic solids (TOS) is removed from the final foods in three food manufacturing processes, the dietary exposure to the food enzyme-TOS was estimated only for the remaining four processes. Dietary exposure was up to 0.087 mg TOS/kg body weight (bw) per day in European populations. When combined with the NOAEL reported in the previous opinion (1000 mg TOS/kg bw per day, the highest dose tested), the Panel derived a margin of exposure of at least 11,494. Based on the data provided for the previous evaluation and the revised margin of exposure, the Panel concluded that this food enzyme does not give rise to safety concerns under the revised intended conditions of use.

Safety evaluation of an extension of use of the food enzyme pectinesterase from the genetically modified Aspergillus oryzae strain AR-962.

The food enzyme pectinesterase (pectin pectylhydrolase; EC 3.1.1.11) is produced with the genetically modified Aspergillus oryzae strain AR-962 by AB Enzymes GmbH. A safety evaluation of this food enzyme was made previously, in which EFSA concluded that this food enzyme did not give rise to safety concerns when used in five food manufacturing processes. Subsequently, the applicant requested to extend its use to two additional processes. In this assessment, EFSA updated the safety evaluation of this food enzyme for uses in a total of seven food manufacturing processes. As the food enzyme-total organic solids (TOS) is removed from the final foods in three food manufacturing processes, the dietary exposure to the food enzyme-TOS was estimated only for the remaining four processes. Dietary exposure was up to 0.575 mg TOS/kg body weight (bw) per day in European populations. When combined with the NOAEL reported in the previous opinion (1000 mg TOS/kg bw per day, the highest dose tested), the Panel derived a margin of exposure of at least 1739. Based on the data provided for the previous evaluation and the revised margin of exposure, the Panel concluded that this food enzyme does not give rise to safety concerns under the revised intended conditions of use.

Safety evaluation of the food enzyme subtilisin from the genetically modified Bacillus licheniformis strain NZYM-CB.

The food enzyme subtilisin (EC 3.4.21.62) is produced with the genetically modified Bacillus licheniformis strain NZYM-CB by Novozymes A/S. The genetic modifications do not give rise to safety concerns. The food enzyme is considered free from viable cells of the production organism and its DNA. It is intended to be used in six food manufacturing processes. The dietary exposure to the food enzyme-TOS was estimated to be up to 0.722 mg TOS/kg body weight (bw) per day in European populations. The production strain of the food enzyme fulfils the requirements for the qualified presumption of safety approach to safety assessment. As no other concerns arising from the manufacturing process were identified, the Panel considered that toxicological tests were not required for the assessment of this food enzyme. A search for the similarity of the amino acid sequence of the food enzyme to known allergens was made and 20 matches were found, including two food allergens (melon and pomegranate). The Panel considered that the risk of allergic reactions by dietary exposure cannot be excluded, particularly in individuals sensitised to melon and pomegranate, but would not exceed the risk from consumption of melon or pomegranate. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.

Safety evaluation of an extension of use of the food enzyme glucan 1,4-α-glucosidase from the non-genetically modified Rhizopus arrhizus strain AE-G.

The food enzyme glucan 1,4-α-glucosidase (4-α-d-glucan glucohydrolase; EC 3.2.1.3) is produced with the non-genetically modified Rhizopus arrhizus strain AE-G by Amano Enzyme Inc. A safety evaluation of this food enzyme was made previously, in which EFSA concluded that this food enzyme did not give rise to safety concerns when used in one food manufacturing process. Subsequently, the applicant requested to extend its use to nine additional processes and revised the use levels. In this assessment, EFSA updated the safety evaluation of this food enzyme for uses in a total of 10 food manufacturing processes. As the food enzyme-total organic solids (TOS) is removed from the final foods in two food manufacturing processes, the dietary exposure to the food enzyme-TOS was estimated only for the remaining eight processes. Dietary exposure was up to 0.424 mg TOS/kg body weight (bw) per day in European populations. When combined with the no observed adverse effect level previously reported (1868 mg TOS/kg bw per day, the highest dose tested), the Panel derived a margin of exposure of at least 4406. Based on the data provided for the previous evaluation and the margin of exposure revised in the present evaluation, the Panel concluded that this food enzyme does not give rise to safety concerns under the revised intended conditions of use.

Safety evaluation of an extension of use of the food enzyme ß-amylase from the non-genetically modified Bacillus flexus strain AE-BAF.

The food enzyme ß-amylase (4-α-d-glucan maltohydrolase, EC 3.2.1.2) is produced with the non-genetically modified Bacillus flexus strain AE-BAF by Amano Enzyme Inc. A safety evaluation of this food enzyme was made previously, in which EFSA concluded that this food enzyme did not give rise to safety concerns when used in three food manufacturing processes. Subsequently, the applicant requested to extend its use to four additional processes and revised the use levels. In this assessment, EFSA updated the safety evaluation of this food enzyme for use in a total of seven food manufacturing processes. As the food enzyme-total organic solids (TOS) are removed from the final foods in one food manufacturing process, the dietary exposure to the food enzyme-TOS was estimated only for the remaining six processes. The dietary exposure was estimated to be up to 0.247 mg TOS/kg body weight per day in European populations. Based on the data provided for the previous evaluation and the dietary exposure revised in the present evaluation, the Panel concluded that this food enzyme does not give rise to safety concerns under the revised intended conditions of use.