Xylanase, endo-1,4-

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

The present test substance, xylanase IUB 3.2.1.8, has been investigated in three in vitro test systems, the Ames test, the in vitro chromosome aberration test and in a cultured human peripheral blood lymphocyte micronucleus assay. All tests have been performed according to current OECD guidelines, and in compliance with GLP. No evidence for genetic toxicity was observed. These results are supported by read-across from four in vitro gene mutation studies in L5178Y mouse lymphoma cells performed on three different amylases belonging to the same subclass of glycosidases (IUBMB class 3.2.1.) as xylanase and further one lipase, belonging to the IUB class 3.1.1.3.

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro gene mutation study in bacteria

Remarks:

Type of genotoxicity: gene mutation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

14 January 2016 - 24 May 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

Adopted 21 July 1997

Deviations:

no

Principles of method if other than guideline:

The ‘treat and plate’ treatment method was used in each test to avoid the possibility that bio-available histidine in the test item might compromise the test.

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Target gene:

The study describes experiments performed to assess the effect of the test material Xylanase in amino acid dependent strains of Salmonella typhimurium and Escherichia coli capable of detecting both induced frame-shift (TA1537 and TA98) and base-pair substitution mutations (TA1535, TA100 and WP2 uvrA pKM101). The test system is a reverse mutation of amino acid dependent bacterial strains.

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2

Metabolic activation:

with and without

Metabolic activation system:

S9 from Aroclor 1254 induced SPF Sprague Dawley rats, manufactured at Molecular Toxicology Incorporated, USA.

Test concentrations with justification for top dose:

The following dose levels, 16, 50, 160, 500, 1600, and 5000 μg TOS/mL were tested in experiment I and 160, 300, 625, 1250, 2500, and 5000 μg TOS/mL were tested in experiment II.

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: Purified water
- Justification for choice of solvent/vehicle: The test substance is water-soluble and any human exposure will be in aqueous solutions.

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

other: 2-nitrofluorene, 4-nitroquinoline 1-oxide, N-methyl-N'-nitrosoguanidine, ICR-191 mutagen and 2-aminoanthracene

Details on test system and experimental conditions:

METHOD OF APPLICATION:
All applications were done in medium before plating, i.e. a liquid culture assay (treat and plate assay).

DURATION
- Exposure duration: 1 hr (liquid culture assay)
- Incubation time (selective incubation) : 2-3 days. The test material was incubated with the microbial cells prior to plating to avoid artifacts due to growth stimulation.

Evaluation criteria:

Individual mutation plate counts from each experiment were recorded separately and the mean and standard deviation of the plate counts for each treatment determined. Mutation plate control counts were compared with the laboratory’s historical control range.
The tests were considered to be valid as all the following criteria were met:
- The vehicle control counts fell within the laboratory’s historical control ranges for this laboratory.
- The positive control chemicals induced increases in revertant numbers of ≥2-fold (in strains TA98, TA100 and WP2 uvrA pKM101) or ≥3-fold (in strains TA1535 and TA1537) the concurrent vehicle control confirming discrimination between different strains, and an active S-9 preparation.
For valid data, the test article was considered to be mutagenic if:
- A concentration related increase in revertant numbers was ≥2-fold (in strains TA98, TA100 and WP2 uvrA pKM101) or ≥3-fold (in strains TA1535 and TA1537) the concurrent vehicle control values.
- The positive trend/effects described above were reproducible.

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

E. coli WP2 uvr A pKM 101

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Positive controls validity:

valid

Additional information on results:

The test item was not toxic to the test bacteria, either in the absence or presence of S-9 mix: no marked reductions in the number of revertant colonies or growth of the background lawn of non-revertant bacteria were observed, compared to the negative control plates in experiment 1.
On the basis of these results, up to 5000 µg TOS/mL was tested in experiment 2.
COMPARISON WITH HISTORICAL CONTROL DATA: The vehicle control plate counts fell within the normal historical ranges and the positive control chemicals all induced increases in revertant numbers as expected. The study thus demonstrated correct strain and assay functioning and was accepted as valid.

Conclusions:

It was concluded, that the results of this Ames test study gave no indication of mutagenic activity of xylanase.

Executive summary:

Xylanase was assayed for mutation in four histidine-requiring strains of S. typhimurium, and one tryptophan-requiring strain of E. coli both in the absence and presence of metabolic activation by a metabolic activation system (S-9 mix), in two separate experiments. A modified ‘treat and plate’ methodology was used for all treatments in this study. All xylanase treatments in this study were performed using formulations prepared in water for irrigation (purified water).

Experiment 1 treatments used a final (nominal) concentration of 16, 50, 160, 500, 1600, and 5000µg TOS/mL Experiment 2 a narrowed concentration intervals were employed covering the range 160-5000µg TOS/mL in order to examine more closely those concentrations approaching the maximum test concentration. Following all treatments there were not clear evidence of toxicity.

Following xylanase treatment of all the test strains in the absence and presence of S-9, no clear and concentration-related increases in revertant numbers were observed that were≥2-fold (in strains TA98, TA100 and WP2 uvrA pKM101) or≥3-fold (in strains TA1535 and TA1537) the concurrent vehicle control. This study was therefore considered to have provided no evidence of any xylanase mutagenic activity in this assay system.

Based on the results obtained in this study and under the assay conditions applied, it is concluded that xylanase is not mutagenic in the Ames test.

Reference 2

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Study period:

26 Oct. 2011 - 10 Feb. 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)

Version / remarks:

adopted 1997

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.10 (Mutagenicity - In Vitro Mammalian Chromosome Aberration Test)

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

in vitro mammalian chromosome aberration test

Test concentrations with justification for top dose:

Range finder: Concentrations tested were between 677.5 and 5420 µg total organic solids (TOS)/mL (677.5 – 1016.3 – 1355.0 – 2032.5 – 2710.0 – 3387.5 – 4065.0 – 4742.5 – 5420.0 µg TOS/mL)
Experiment 1: concentrations of the test item up to 4742.5 µg TOS/mL with S9 and up to 3387.5 µg TOS/mL without S9 were tested
Experiment 2: concentrations of the test item up to 5420.0 µg TOS/mL without S9 were tested

Vehicle / solvent:

Sterile deionised water
Justification for choice of solvent/vehicle: Substance is water-soluble and any human exposure will be in aqueous solutions.

Negative solvent / vehicle controls:

yes

Remarks:

sterile deionised water

Positive controls:

yes

Positive control substance:

cyclophosphamide

ethylmethanesulphonate

Details on test system and experimental conditions:

Test item was accurately measured and dissolved in deionised water just before dosing the test system. The final conc of deionised water in the culture medium was 10% v/v. There was no significant change in solubility, pH value or osmolarity when the test item was dosed into media. Nine concentrations of xylanase were used in the preliminary assay for the selection of dose levels in the main studies. Doses were then selected for the two main assays ideally with the highest dose level inducing a toxic effect (50% reduction in mitotic index). In the absence of cytotoxicity, the highest dose selected would be 5420 µg total organic solids (TOS)/mL in agreement with the OECD guideline.

The used metabolic activation system was rat liver homogenate, S-9 mix. The positive controls were: Ethylmethane sulfonate (EMS) for assays without metabolic activation (Acros Organics) and Cyclophosphamide (CPA) for assays with metabolic activation (Sigma-Aldrich Chemie).

Duplicate cultures of V79 cells of the Chinese Hamster, treated with the test material, were evaluated for chromosome aberrations at selected dose levels, together with negative control (solvent control: Deionised water 10%) and positive controls.  The treatment conditions used for the study were: In Experiment I, the exposure period was 4 hours with and without S9 mix. In Experiment II, the exposure period was 18 hours without S9 mix. The chromosomes were prepared 18 hours (Exp. I & II) after start of treatment with the test item. Mitosis was arrested by addition of Colcemid (0.2 µg/mL) 15.5 hours after start of the treatment.

Evaluation criteria:

Breaks, fragments, deletions, exchanges and chromosomal disintegrations were recorded as structural chromosome aberrations. Gaps were recorded as well, but they were not included in the calculation of the aberration rates. At least 100 well spread metaphase plates per culture were scored for cytogenetic damage on coded slides. Only metaphases with characteristic chromosome numbers of 22 ± 1 centromer regions were included in the analysis. To describe a cytotoxic effect the mitotic index (% cells in mitosis) was determined.

Statistics:

The frequency of cells with aberrations excluding gaps and the frequency of polyploid cells was compared, where necessary, with the concurrent vehicle control value using Fisher's Exact test.

Key result

Species / strain:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Positive controls validity:

valid

Additional information on results:

In the preliminary assay, clear cytotoxicity was noted at the dose ≥2032.5 µg total organic solids (TOS)/mL without S9 mix and at the dose ≥2710.0 µg total organic solids (TOS)/mL with S9 mix. Therefore, the following doses were selected for the evaluation of the cytogenetic damage in two experiments, Experiment I, 1016.3 – 1355.0 – 2032.5 µg TOS/mL without S9 and 2032.5 – 2710.0 – 3387.5µg TOS/mL with S9, and Experiment II: 1016.3 – 2710.0 – 3387.5 – 4065.0 µg TOS/mL (without S9).
In experiment I in the absence and presence of S-9 mix, and in experiment II in the absence of S-9 mix, clear cytotoxicity was observed, however no biologically relevant increase in the number of cells with structural chromosomal aberrations was observed. No evidence of an increase in polyploidy metaphases was recorded with the test article. Distinct increases in structural chromosomal aberrations were found with the positive controls, ethylmethane sulfonate and cyclophosphamide.

Conclusion: Non-clastogenic in vitro.

Conclusions:

Xylanase is not clastogenic in the in vitro cytogenetic test using cultured Chinese Hamster V79 cells in both the presence and absence of metabolic activation.

Executive summary:

The objective of this assay was to investigate the potential of xylanase to induce numerical and/or structural changes in the chromosome of mammalian systems (i.e., Chinese Hamster V79 cells) in both the presence and absence of metabolic activation (induced rat liver; S-9 mix). This assay was conducted in accordance with OECD guideline No. 473 and complied with GLP. 

A preliminary cytotoxicity test was performed as a dose range finder using 9 concentrations of xylanase and a solvent and a positive control. Doses selected for the main tests (Experiment I and II) were based on cytotoxicity, which was characterized by the percentage of mitotic suppression in comparison to controls. In the preliminary assay, clear cytotoxicity was noted at the dose ≥2032.5 µg total organic solids (TOS)/mL without S9 mix and at the dose ≥2710.0 µg total organic solids (TOS)/mL with S9 mix. Therefore, the following doses were selected for the evaluation of the cytogenetic damage in two experiments, Experiment I, 1016.3 – 1355.0 – 2032.5 µg TOS/mL without S9 and 2032.5 – 2710.0 – 3387.5µg TOS/mL with S9, and Experiment II: 1016.3 – 2710.0 – 3387.5 – 4065.0 µg TOS/mL (without S9). The 5000 µg TOS/mL is the highest dose recommended by the OECD guideline. 

In Experiment I, the exposure period was 4 hours for assays with and without S-9 mix. In Experiment II, the exposure period was 18 hours without S-9 mix. In both experiments, colcemid was added to the cultures 2.5 hours prior to harvesting. Cells were then harvested, collected, suspended, fixed, and evaluated.

In this study, in both experiment I and II, cytotoxicity was observed, however no biologically relevant increase in the number of cells with structural chromosomal aberrations was observed. No evidence of an increase in polyploidy metaphases was recorded with the test article. Significant increases in structural chromosomal aberrations were found with the positive controls, ethylmethane sulfonate for assays without S-9 mix and cyclophosphamide for assays with S-9 mix.

Xylanase is to be classified as “Non-Clastogenic” in this in vitro cytogenetic test using cultured Chinese Hamster V79 cells both in the presence and absence of metabolic activation.

 

GHS Classification: Not classified

Reference 3

Endpoint:

in vitro cytogenicity / micronucleus study

Remarks:

Type of genotoxicity: other: Chromosome aberration/clastogenicity and aneuploidy

Type of information:

experimental study

Adequacy of study:

key study

Study period:

13. January 2016 - 22. April 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 487 (In vitro Mammalian Cell Micronucleus Test)

Version / remarks:

Adopted 26 sep 2014

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

in vitro mammalian cell micronucleus test

Species / strain / cell type:

lymphocytes: Primary cells from human blood

Metabolic activation:

with and without

Metabolic activation system:

S9 mix

Test concentrations with justification for top dose:

Highest concentration tested was 5000 µg TOS/mL and dilutions hereof.

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: Purified water
- Justification for choice of solvent/vehicle: Substance is water-soluble and any human exposure will be in aqueous solutions.

Negative solvent / vehicle controls:

yes

Remarks:

Purified water

Positive controls:

yes

Positive control substance:

other: Mitomycin C (MMC) and Vinblastine (VIN) in the absence of rat liver S-9, Cyclophosphamide (CPA) in the presence of S-9.

Details on test system and experimental conditions:

METHOD OF APPLICATION:
Whole blood cultures were established in sterile disposable centrifuge tubes by placing 0.4 mL of pooled heparinized blood into 8.1 mL pre-warmed (in an incubator set to 37±1°C) HEPES-buffered RPMI medium containing 10% (v/v) heat inactivated fetal calf serum and 0.52% penicillin / streptomycin, so that the final volume following addition of S-9 mix/KCl and the test article in its chosen vehicle was 10 mL. The mitogen Phytohaemagglutinin (PHA, reagent grade) was included in the culture medium at a concentration of approximately 2% of culture to stimulate the lymphocytes to divide. Blood cultures were incubated at 37±1°C for approximately 48 hours and rocked continuously.

Sets of duplicate cultures were exposed to the test substance for 3 hours in the absence and presence of metabolic activation (S-9 mix) and harvested 24 hours after the beginning of treatment (3+21 hour treatment). Additionally, a continuous 24-hour treatment without S-9 mix was included with harvesting at the end of treatment (24+24 hour treatment). For removal of the test article, cells were pelleted (approximately 300 g, 10 minutes), washed twice with sterile saline (pre-warmed in an incubator set to 37 ± 1°C), and re-suspended in fresh pre-warmed medium containing foetal calf serum and penicillin / streptomycin. Cytochalasin-B (at a final concentration of 6 μg/mL per culture) was added to post wash off culture medium to block cytokinesis.

Three concentrations, covering an appropriate range of cytotoxicity, were selected for scoring of micronuclei by evaluating the effect of the test substance on the replication index. Were possible, 2000 cells per concentration (500 cells from each replicate culture, 1000 cells per culture) were scored.

DURATION
- pre-incubation after PHA stimulation: 48 hours
- Exposure duration: 3 (+21 recovery; +/-S-9 treatments) and 24 (+24 recovery; -S-9 treatments) hours

NUMBER OF REPLICATIONS: Sets of duplicate cultures were exposed to the test substance, in at least two independent experiments.

Evaluation criteria:

A test article was considered positive if:
- the assay was valid, and
- significant increase in the frequency of MNBN cells at one or more concentrations , and
- the incidence of MNBN cells exceeded the normal range in both replicates, and
- a concentration-related increase in the proportion of MNBN cells was observed.

Statistics:

The proportion of MNBN cells for each treatment condition were compared with the proportion in negative controls by using Fisher's exact test. A Cochran-Armitage trend test was applied to each treatment condition. Probability values of p equal or less than 0.05 were accepted as significant.

Species / strain:

lymphocytes: from human blood

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

In the 24+0 hour treatment without S-9 mix the highest applied concentration was 1000 µg/mL due to cytotoxicity at higher concentrations. No significant cytotoxicity was seen in the 3+21 hour treatment.

Vehicle controls validity:

valid

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Effects of pH: No marked changes in pH (shift of greater than 1 pH unit) was observed.
- Effects of osmolality: no marked changes in osmolality (shifts greater than 50 mOsm/kg) were observed.
- Water solubility: yes
- Precipitation: no

RANGE-FINDING/SCREENING STUDIES: Preliminary cytotoxicity range-finder was performed.

COMPARISON WITH HISTORICAL CONTROL DATA:
The negative and positive controls were within the historical negative control ranges.

Conclusions:

Xylanase did not show any clastogenic activity, neither in the presence or absence of S-9 mix, when tested in the present in vitro micronucleus assay.

Executive summary:

Xylanase was tested in an in vitro micronucleus assay using duplicate human lymphocyte cultures prepared from the pooled blood of two male donors in a single experiment. Treatments covering a broad range of concentrations, separated by narrow intervals, were performed both in the absence and presence of metabolic activation (S-9) from Aroclor 1254-induced rats. The test article was formulated in water for irrigation (purified water) and the highest concentration tested in the Micronucleus Experiment, 5000 μg TOS/mL was determined following a preliminary cytotoxicity Range-Finder Experiment. Treatments were conducted 48 hours following mitogen stimulation by phytohaemagglutinin (PHA). The test article concentrations for micronucleus analysis were selected by evaluating the effect of Xylanase on the replication index (RI). Three concentrations, covering an appropriate range of cytotoxicity, were selected for scoring of micronuclei.

All acceptance criteria were considered met and the study was therefore accepted as valid.

Treatment of cells with Xylanase in the absence and presence of S-9 resulted in frequencies of MNBN cells which were similar to and not significantly higher than those observed in concurrent vehicle controls for all concentrations analyzed (all treatments). With the exception of a single replicate culture at the lowest and intermediate concentrations analyzed post 3+21 hour +S-9 treatment, the MNBN cell frequency of all Xylanase treated cultures (all concentrations) fell within the normal range. There were no indications of any test article concentration related effect on MNBN cell frequency (negative Cochran-Armitage trend).

It was concluded that Xylanase did not induce micronuclei in cultured human peripheral blood lymphocytes following treatment in the absence and presence of a rat liver metabolic activation system (S-9). Concentrations were tested up to 5000 μg TOS/mL, a recommended regulatory maximum concentration for in vitro micronucleus assays.

Reference 4

Endpoint:

in vitro gene mutation study in mammalian cells

Remarks:

Type of genotoxicity: gene mutation

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

other information

Justification for type of information:

According to the ECHA Guidance Chapter R 7a: Endpoint specific guidance (version 2, Nov 2012), the following studies on genetic toxicity are required: In vitro gene mutation study in bacteria and one of the following, in vitro cytogenicity study in mammalian cells or an in vitro micronucleus study. In case these studies are both negative, an in vitro gene mutation study in mammalian cells is requested in addition.
The present test substance, xylanase IUB 3.2.1.8, has been investigated in three in vitro test systems, the Ames test, the in vitro chromosome aberration test and in a cultured human peripheral blood lymphocyte micronucleus assay. All tests have been performed according to current OECD guidelines, and in compliance with GLP. No evidence for genetic toxicity was observed. These results are supported by read-across from four in vitro gene mutation studies in L5178Y mouse lymphoma cells performed on three different amylases belonging to the same subclass of glycosidases (IUBMB class 3.2.1.) as xylanase and further one lipase, belonging to the IUB class 3.1.1.3.
The safety of the production strain is fully documented to belong to a safe strain lineage (Pariza and Johnson, 2001; Enzymes REACH Consortium, 2009) and the enzyme concentrate is well characterized. All enzyme classes are hydrophilic and readily biodegradable and in general, non-protease enzymes exhibit the same toxicological properties and although they are potential respiratory sensitizers, they are considered to be of low toxicity, confirmed by toxicity studies performed and published by the industry (summarized in Basketter et al. 2012a and 2012b). The physico-chemical properties of enzymes including logKow are very similar. They are further proteins built up of amino acids and the type, order and number of the amino acids in the polymer differs between enzymes, determining the 3-dimensional structure, the activity and specificity of the individual enzyme type. Industrial production strains typically have a long history of safe use for many years in the production of technical and also often food grade enzymes.
Because all enzymes are built up of the same amino acids the physical and chemical characteristics will be very similar for different enzymes, and hence read-across from other non-proteolytic enzymes (e.g. amylase and lipase) should be fully applicable.
The overall conclusion is that xylanase is not mutagenic and does not induce genotoxicity in the present test systems.

References
- Pariza, M. W., and Johnson, E. A. (2001). Evaluating the Safety of Microbial Enzyme Preparations Used in Food Processing: Update for a New Century. Regulatory Toxicology and Pharmacology, 33: 173-186.
- Enzymes REACH Consortium: Safety evaluation of technical enzyme products with regards to the REACH legislation. Document from Manufacturers, Importers and/or Only Representatives of one or more enzymes, who are subject to the registration requirements pursuant to REACH, 2009. http://www.enzymes-reach.org/documents.html
- D. Basketter; N. Berg; F. Kruszewski; K. Sarlo; B. Concoby. The Toxicology and Immunology of Detergent Enzymes. 2012a. J. Immunotox 9(3): 320-6.
- Basketter D., Berg N., Broekhuizen C., Fieldsend M., Kirkwood S., Kluin C., Mathieu S. and Rodriguez C. Enzymes in Cleaning Products: An Overview of Toxicological Properties and Risk Assessment/Management. 2012b. Reg. Toxicol. Pharmacol, 64/1: 117-123

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Conclusions:

The conclusion is that the target substance xylanase IUBMB 3.2.1.8 is not genotoxic.

Executive summary:

The present test substances, three different amylases belonging to the same subclass of glycosidases (IUBMB class 3.2.1.) as the target material xylanase and further one lipase, belonging to the IUBMB class 3.1.1.3, have been tested in in vitro gene mutation studies in L5178Y mouse lymphoma cells. All tests have been performed according to current OECD guidelines, and in compliance with GLP. No evidence for genetic toxicity was observed. This supports the conclusion that the target substance xylanase IUBMB 3.2.1.8 is not genotoxic.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Additional information from genetic toxicity in vitro:

The present test substance, xylanase IUB 3.2.1.8, has been investigated in three in vitro test systems, the Ames test, the in vitro chromosome aberration test and in a cultured human peripheral blood lymphocyte micronucleus assay. All tests have been performed according to current OECD guidelines, and in compliance with GLP. No evidence for genetic toxicity was observed. The results were supported by read-across from four in vitro gene mutation studies in L5178Y mouse lymphoma cells performed on three different amylases belonging to the same subclass of glycosidases (IUBMB class 3.2.1.) as xylanase and further one lipase, belonging to the IUB class 3.1.1.3. The safety of the production strains is fully documented to belong to safe strain lineages (Pariza and Johnson, 2001) and the enzyme test material was well characterized. Because enzymes are built up of the same amino acids, the physical and chemical characteristics will be very similar for different enzymes, and hence read-across from other non-proteolytic enzymes (e.g. amylase and lipase) should be fully applicable.

Xylanase is concluded not to be genotoxic.

Reference:

Pariza, M. W., and Johnson, E. A. (2001). Evaluating the Safety of Microbial Enzyme Preparations Used in Food Processing: Update for a New Century. Regulatory Toxicology and Pharmacology, 33: 173-186. 

Justification for selection of genetic toxicity endpoint

The present test substance, xylanase IUB 3.2.1.8, has been investigated in three in vitro test systems, the Ames test, the in vitro chromosome aberration test and in a cultured human peripheral blood lymphocyte micronucleus assay. All tests have been performed according to current OECD guidelines, and in compliance with GLP. No evidence for genetic toxicity was observed. The production strains of xylanase meet the criteria for safe strain production micro-organisms.These results are supported by read-across from four in vitro gene mutation studies in L5178Y mouse lymphoma cells performed on three different amylases belonging to the same subclass of glycosidases (IUBMB class 3.2.1.) as xylanase and further one lipase, belonging to the IUB class 3.1.1.3.

Justification for classification or non-classification

Due to the lack of genetic toxicity xylanase is not classified.