Safety evaluation of the food enzyme subtilisin from the non-genetically modified Bacillus paralicheniformis strain AP-01.

The food enzyme subtilisin (EC 3.4.21.62) is produced with the non-genetically modified Bacillus paralicheniformis strain AP-01 by Nagase (Europa) GmbH. It was considered free from viable cells of the production organism. The food enzyme is intended to be used in five food manufacturing processes. Since residual amounts of food enzyme-total organic solids (TOS) are removed in one process, dietary exposure was calculated only for the remaining four food manufacturing processes. It was estimated to be up to 0.875 mg TOS/kg body weight per day in European populations. The production strain of the food enzyme has the capacity to produce bacitracin and thus failed to meet the requirements of the Qualified Presumption of Safety approach. Bacitracin was detected in the industrial fermentation medium but not in the food enzyme itself. However, the limit of detection of the analytical method used for bacitracin was not sufficient to exclude the possible presence of bacitracin at a level representing a risk for the development of antimicrobial resistant bacteria. A search for the similarity of the amino acid sequence of the food enzyme to known allergens was made and twenty-eight matches with respiratory allergens, one match with a contact allergen and two matches with food allergens (melon and pomegranate) were found. The Panel considered that the risk of allergic reactions upon dietary exposure to this food enzyme, particularly in individuals sensitised to melon or pomegranate, cannot be excluded, but would not exceed the risk of consuming melon or pomegranate. Based on the data provided, the Panel could not exclude the presence of bacitracin, a medically important antimicrobial, and consequently the safety of this food enzyme could not be established.

Safety evaluation 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. The food enzyme is intended to be used in eight food manufacturing processes. Since residual amounts of food enzyme-total organic solids (TOS) are removed in two food manufacturing processes, dietary exposure was calculated only for the remaining six processes. It was estimated to be up to 0.056 mg TOS/kg body weight 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. Consequently, in the absence of other concerns, the Panel considered that toxicological studies were not needed for the safety 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 two matches with respiratory allergens were found. The Panel considered that the risk of allergic reactions upon dietary exposure to this food enzyme cannot be excluded (except for the production of distilled alcohol), 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.

Taxonomic identity of the Bacillus licheniformis strains used to produce food enzymes evaluated in published EFSA opinions.

Bacillus paralicheniformis, a species known to produce the antimicrobial bacitracin, could be misidentified as Bacillus licheniformis, depending on the identification method used. For this reason, the European Commission requested EFSA to review the taxonomic identification of formerly assessed B. licheniformis production strains. Following this request, EFSA retrieved the raw data from 27 technical dossiers submitted and found that the taxonomic identification was established by 16S rRNA gene analyses for 15 strains and by whole genome sequence analysis for 12 strains. As a conclusion, only these 12 strains could be unambiguously identified as B. licheniformis.

Safety evaluation of the food enzyme preparation D-psicose 3-epimerase from the non-genetically modified Microbacterium foliorum strain SYG27B.

This assessment addresses a food enzyme preparation consisting of the immobilised non-viable cells of the non-genetically modified bacterium identified by the applicant (Samyang Corporation) as Microbacterium foliorum strain SYG27B. This strain produces the enzyme D-psicose 3-epimerase (EC 5.1.3.30). The food enzyme preparation is used for the isomerisation of fructose to produce the speciality carbohydrate D-allulose (synonym D-psicose). Since the hazard identification and characterisation could not be made and the identity of the production organism could not be established, the Panel was unable to complete the assessment of this food enzyme preparation containing D-psicose 3-epimerase.

Safety evaluation of the food enzyme microbial collagenase from the genetically modified Streptomyces violaceoruber strain pCol.

The food enzyme microbial collagenase (EC 3.4.24.3) is produced with the genetically modified Streptomyces violaceoruber strain pCol by Nagase (Europa) 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 two food manufacturing processes: the production of modified meat and fish products and the production of protein hydrolysates from meat and fish proteins. The dietary exposure to the food enzyme-total organic solids (TOS) was estimated to be up to 1.098 mg TOS/kg body weight (bw) per day in European populations. 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 940 mg TOS/kg bw per day, the highest dose tested, which, when compared with the estimated dietary exposure, resulted in a margin of exposure of at least 856. 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 the food enzyme mucorpepsin from the non-genetically modified Rhizomucor miehei strain M19-21.

The food enzyme mucorpepsin (EC 3.4.23.23) is produced with the non-genetically modified Rhizomucor miehei strain M19-21 by Meito Sangyo Co., Ltd. The enzyme is chemically modified to produce a thermolabile form. The food enzyme was considered free from viable cells of the production organism. It is intended to be used in the processing of dairy products for the production of cheese and fermented dairy products. Based on the maximum use levels, dietary exposure was estimated to be up to 0.108 mg TOS/kg body weight (bw) per day in European populations. 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 226 mg TOS/kg bw per day, the highest dose tested, which, when compared with the estimated dietary exposure, results in a margin of exposure of at least 2093. A search for the similarity of the amino acid sequence of the food enzyme to known allergens was made and four matches to respiratory allergens and one match to a food allergen (mustard) were found. The Panel considered that the risk of allergic reactions upon dietary exposure to this food enzyme, particularly in individuals sensitised to mustard proteins, cannot be excluded. 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 α-amylase from the non-genetically modified Bacillus amyloliquefaciens strain NZYM-WR.

The food enzyme α-amylase (4-α-d-glucan glucanohydrolase; EC 3.2.1.1) is produced with the non-genetically modified Bacillus amyloliquefaciens strain NZYM-WR by Novozymes A/S. The production strain met the requirements for the qualified presumption of safety (QPS) approach. The food enzyme is intended to be used in nine food manufacturing processes: processing of cereals and other grains for the production of baked products, cereal-based products other than baked, glucose syrups and other starch hydrolysates, distilled alcohol and brewed products; production of refined and unrefined sugar, production of plant-based analogues of milk and milk products; processing of fruits and vegetables for the production of juices and fruit and vegetable products other than juices. Since residual amounts of total organic solids (TOS) are removed during two processes, a dietary exposure was calculated only for the remaining seven food manufacturing processes. Exposure was estimated to be up to 0.450 mg TOS/kg body weight per day in European populations. As the production strain qualified for the QPS approach and no issues of concern arose from the production process of the food enzyme, the Panel considered that toxicological studies were unnecessary. 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 upon dietary exposure to this food enzyme cannot be excluded (except for distilled alcohol production), 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 subtilisin from the non-genetically modified Bacillus licheniformis strain NZYM-CX.

The food enzyme subtilisin (EC 3.4.21.62) is produced with the non-genetically modified Bacillus licheniformis strain NZYM-CX by Novozymes A/S. The production strain met the requirements for the qualified presumption of safety (QPS) approach. The food enzyme is intended to be used in eight food manufacturing processes: processing of cereals and other grains for the production of brewed products; processing of dairy products for the production of modified milk proteins and flavouring preparations; processing of plant- and fungal-derived products for the production of plant-based analogues of milk and milk products, protein hydrolysates and edible oils from algae; processing of meat and fish products for the production of protein hydrolysates; processing of yeast and yeast products. Since residual amounts of total organic solids (TOS) are removed in the production of edible oils from algae, dietary exposure was calculated only for the remaining seven food manufacturing processes. Exposure was estimated to be up to 2.393 mg TOS/kg body weight (bw) per day in European populations. As the production strain qualified for the QPS approach and no issues of concern arose from the production process of the food enzyme, the Panel considered that toxicological studies were unnecessary. A search for the similarity of the amino acid sequence of the food enzyme to known allergens was performed, and a total of 20 matches were found, 17 to respiratory allergens, two to food allergens (found in muskmelon and pomegranate) and one to a contact allergen. The Panel considered that the risk of allergic reactions upon dietary exposure to this food enzyme cannot be excluded, especially in individuals sensitised to muskmelon or pomegranate, but would not exceed the risk of consuming these foods. 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 MAMDSM.

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 MAMDSM by DSM Food Specialties. 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 cereals and other grains for the production of baked and brewed products. Dietary exposure to the food enzyme-total organic solids (TOS) was estimated to be up to 0.204 mg TOS/kg body weight (bw) per day in European populations. The production strain meets the requirements for the QPS approach. As no concerns arising from the manufacturing process have been identified, the Panel considered that toxicological tests were not needed 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 four matches were 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 the food enzyme α-amylase from the non-genetically modified Bacillus amyloliquefaciens strain LMG-S 32676.

The food enzyme α-amylase (4-α-d-glucan glucanohydrolase; EC 3.2.1.1) is produced with the non-genetically modified microorganism Bacillus amyloliquefaciens strain LMG-S 32676 by Enmex SA de CV, a Kerry Company. The food enzyme under assessment is intended to be used in six food manufacturing processes: baking processes, brewing processes, distilled alcohol production, starch processing for the production of glucose syrups and other starch hydrolysates, refined and unrefined sugar production and yeast processing. Since residual amounts of total organic solids (TOS) are removed in distilled alcohol production and starch processing for glucose syrups production and other starch hydrolysates, the dietary exposure estimation was made only for the remaining four food processes. It was estimated to be up to 2.998 mg TOS/kg body weight per day in European populations. The production strain meets the requirements for the QPS approach. As no concerns arising from the manufacturing process were identified, the Panel considered that toxicological tests were not needed 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 two matches with respiratory allergens were found. The Panel considered that a risk of allergic reactions upon dietary exposure to this food enzyme cannot be excluded (except for distilled alcohol production), 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 α-amylase from the non-genetically modified Bacillus licheniformis strain T74.

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 T74 by Novozymes A/S. The production strain met the qualifications of the qualified presumption of safety (QPS) approach. The food enzyme is intended to be used in eight food manufacturing processes: starch processing for the production of glucose syrups and other starch hydrolysates, distilled alcohol production, refined and unrefined sugar production, brewing processes, cereal-based processes, fruit and vegetable processing for juice production, fruit and vegetable processing for products other than juices and the production of dairy analogues. Since residual amounts of total organic solids (TOS) are removed during two food processes (starch processing for the production of glucose syrups and other starch hydrolysates, distilled alcohol production), dietary exposure was calculated only for the remaining six food manufacturing processes. It was estimated to be up to 0.291 mg TOS/kg body weight per day in European populations. Since the production strain meets the requirements for the QPS approach and no issues of concern arose from the production process of the food enzyme, the Panel considered that toxicological studies were unnecessary. 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 to this food enzyme cannot be excluded (except for distilled alcohol production), 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 subtilisin from the non-genetically modified Bacillus paralicheniformis strain DP-Dzx96.

The food enzyme subtilisin (serine endopeptidase, EC 3.4.21.62) is produced with the non-genetically modified Bacillus paralicheniformis strain DP-Dzx96 by Genencor International B.V. The food enzyme was considered free from viable cells of the production organism. The food enzyme is intended to be used in five food manufacturing processes: production of protein hydrolysates from plants and fungi, production of protein hydrolysates from meat and fish proteins, production of cooked rice, production of modified meat and fish products, and yeast processing. The production strain of the food enzyme contains known antimicrobial resistance genes. Bacitracin, a medically important antimicrobial, was detected in the food enzyme. The presence of bacitracin represents a risk for the development of antimicrobial resistant bacteria. A search for the similarity of the amino acid sequence of the food enzyme to known allergens was made and three matches with respiratory and two matches with food allergens were found. The Panel considered that, under the intended conditions of use, the risk of allergic reactions upon dietary exposure to this food enzyme, particularly in individuals sensitised to muskmelon or pomegranate, cannot be excluded, but would not exceed the risk of consuming these foods. Due to the presence of bacitracin, the Panel concluded that the food enzyme subtilisin produced with the non-genetically modified Bacillus paralicheniformis strain DP-Dzx96 cannot be considered safe.

Safety evaluation of the food enzyme α-amylase from the non-genetically modified Bacillus amyloliquefaciens strain BA.

The food enzyme α-amylase (4-α-d-glucan glucanohydrolase; EC 3.2.1.1) is produced with the non-genetically modified microorganism Bacillus amyloliquefaciens strain BA by HBI Enzymes Inc. The enzyme under assessment is intended to be used in six food processes: baking processes, brewing processes, distilled alcohol production, starch processing for the production of glucose syrups and other starch hydrolysates, production of dairy analogues and production of rice-based meals. Since residual amounts of total organic solids (TOS) are removed during distillation and during the production of glucose syrups and other starch hydrolysates, dietary exposure was calculated only for the remaining four food manufacturing processes. It was estimated to be up to 4.805 mg TOS/kg body weight (bw) per day in European populations. The applicant did not provide sufficient data to demonstrate that the production strain meets the qualified presumption of safety (QPS) criteria, or proof of absence of viable cells and DNA from the production organism in the food enzyme. Therefore, the Panel was not able to conclude on the safety of the microbial source. A margin of exposure could not be calculated in the absence of toxicological studies. A search for the similarity of the amino acid sequence of the food enzyme to known allergens was made and two matches with respiratory allergens were found. The Panel considered that, under the intended conditions of use (other than distilled alcohol production), the risk of allergic reactions by dietary exposure cannot be excluded, but the likelihood is low. Based on the data provided, the Panel could not conclude on the safety of this food enzyme, under the intended conditions of use.

Safety evaluation of the food enzyme endo-1,4-ß-xylanase from the genetically modified Bacillus subtilis strain XAN.

The food enzyme endo-1,4-ß-xylanase (4-ß-d-xylan xylanohydrolase, EC 3.2.1.8) is produced with the genetically modified microorganism Bacillus subtilis strain XAN 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. The production strain of the food enzyme contains antimicrobial resistance genes. However, based on the absence of viable cells and DNA from the production organism in the food enzyme, this is not considered to be a risk. The food enzyme is intended to be used in baking processes and cereal-based processes. Dietary exposure to the food enzyme total organic solids (TOS) was estimated to be up to 0.02 mg TOS/kg body weight (bw) per day in European populations. As no other concerns arising from the microbial source and its subsequent genetic modification or from the manufacturing process have been identified, the Panel considered that toxicological tests are not needed for the assessment of this food enzyme. A search for 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 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 subtilisin from the non-genetically modified Bacillus paralicheniformis strain LMG S-30155.

The food enzyme subtilisin (serine endopeptidase, EC 3.4.21.62) is produced with the non-genetically modified microorganism Bacillus paralicheniformis strain LMG S-30155 by ENMEX SA de CV, now part of Kerry Food Ingredients (Cork) Ltd. The food enzyme is intended to be used in oil production, hydrolysis of vegetable/microbial/animal proteins, yeast processing and production of flavouring preparations. The production strain of the food enzyme contains known antimicrobial resistance genes and genes involved in bacitracin biosynthesis. Consequently, it does not fulfil the requirements for the QPS approach to safety assessment. Bacitracin was detected in the food enzyme and the ■■■■■ The presence of bacitracin, a medically important antimicrobial, in the food enzyme represents a risk for the development of resistance in bacteria. Due to the presence of bacitracin, the Panel concluded that the food enzyme subtilisin produced with the non-genetically modified Bacillus paralicheniformis strain LMG S-30155 cannot be considered safe.

Safety evaluation of the food enzyme glucan 1,4-α-glucosidase from the non-genetically modified Aspergillus niger strain NZYM-BO.

The food enzyme glucan 1,4-α-glucosidase (4-α-d-glucan α-glucohydrolase; EC 3.2.1.3) is produced with the non-genetically modified Aspergillus niger strain NZYM-BO by Novozymes A/S. It was considered free from viable cells of the production organism. It is intended to be used in seven food manufacturing processes: baking processes, brewing processes, cereal-based processes, distilled alcohol production, fruit and vegetable processing for juice production, production of dairy analogues and starch processing for the production of glucose syrups and other starch hydrolysates. Since residual amounts of total organic solids (TOS) are removed by distillation and during starch processing, dietary exposure was not calculated for these two food manufacturing processes. For the remaining five food manufacturing processes, dietary exposure to the food enzyme-TOS was estimated to be up to 2.97 mg TOS/kg body weight (bw) per day in European populations. 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 1,920 mg TOS/kg bw per day, the highest dose tested, which, when compared with the estimated dietary exposure, resulted in a margin of exposure of at least 646. 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, under the intended conditions of use, the risk of allergic reactions by dietary exposure to this food enzyme cannot be excluded (except for distilled alcohol production), 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 asparaginase from the genetically modified Aspergillus oryzae strain NZYM-OA.

The food enzyme asparaginase (l-asparagine amidohydrolase; EC 3.5.1.1) is produced with the genetically modified microorganism Aspergillus oryzae strain NZYM-OA by Novozymes A/S. 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 various food manufacturing processes to prevent acrylamide formation. Dietary exposure to the food enzyme-total organic solids (TOS) was estimated to be up to 0.051 mg TOS/kg body weight (bw) per day in European populations. 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 1,182 mg TOS/kg bw per day, the highest dose tested, which, when compared with the estimated dietary exposure, resulted in a margin of exposure of at least 23,176. 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 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 d-tagatose 3-epimerase from the genetically modified Escherichia coli strain PS-Sav-001.

The food enzyme d-tagatose 3-epimerase (EC 5.1.3.31) is produced with the genetically modified Escherichia coli strain PS-Sav-001 by SAVANNA Ingredients GmbH. 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. The food enzyme is used while retained inside a membrane reactor to convert d-fructose into the speciality carbohydrate d-allulose (syn. d-psicose). Since residual amounts of total organic solids (TOS) are removed by the purification steps applied during the production of d-allulose, dietary exposure was not calculated and toxicological studies were not considered necessary. 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 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.

Ubiquitin-protein ligase Ubr5 cooperates with hedgehog signalling to promote skeletal tissue homeostasis.

Mammalian Hedgehog (HH) signalling pathway plays an essential role in tissue homeostasis and its deregulation is linked to rheumatological disorders. UBR5 is the mammalian homologue of the E3 ubiquitin-protein ligase Hyd, a negative regulator of the Hh-pathway in Drosophila. To investigate a possible role of UBR5 in regulation of the musculoskeletal system through modulation of mammalian HH signaling, we created a mouse model for specific loss of Ubr5 function in limb bud mesenchyme. Our findings revealed a role for UBR5 in maintaining cartilage homeostasis and suppressing metaplasia. Ubr5 loss of function resulted in progressive and dramatic articular cartilage degradation, enlarged, abnormally shaped sesamoid bones and extensive heterotopic tissue metaplasia linked to calcification of tendons and ossification of synovium. Genetic suppression of smoothened (Smo), a key mediator of HH signalling, dramatically enhanced the Ubr5 mutant phenotype. Analysis of HH signalling in both mouse and cell model systems revealed that loss of Ubr5 stimulated canonical HH-signalling while also increasing PKA activity. In addition, human osteoarthritic samples revealed similar correlations between UBR5 expression, canonical HH signalling and PKA activity markers. Our studies identified a crucial function for the Ubr5 gene in the maintenance of skeletal tissue homeostasis and an unexpected mode of regulation of the HH signalling pathway.

Fibroblast growth factors (FGFs) prime the limb specific Shh enhancer for chromatin changes that balance histone acetylation mediated by E26 transformation-specific (ETS) factors.

Sonic hedgehog (Shh) expression in the limb bud organizing centre called the zone of polarizing activity is regulated by the ZRS enhancer. Here, we examine in mouse and in a mouse limb-derived cell line the dynamic events that activate and restrict the spatial activity of the ZRS. Fibroblast growth factor (FGF) signalling in the distal limb primes the ZRS at early embryonic stages maintaining a poised, but inactive state broadly across the distal limb mesenchyme. The E26 transformation-specific transcription factor, ETV4, which is induced by FGF signalling and acts as a repressor of ZRS activity, interacts with the histone deacetylase HDAC2 and ensures that the poised ZRS remains transcriptionally inactive. Conversely, GABPα, an activator of the ZRS, recruits p300, which is associated with histone acetylation (H3K27ac) indicative of an active enhancer. Hence, the primed but inactive state of the ZRS is induced by FGF signalling and in combination with balanced histone modification events establishes the restricted, active enhancer responsible for patterning the limb bud during development.