Safety evaluation of an α-cyclodextrin glycosyltranferase preparation

Pharmacokinetics and pharmacodynamics of cyclodextrin-based oral drug delivery formulations for disease therapy

Oral drug administration has become the most common and preferred mode of disease treatment due to its good medication adherence and convenience. For orally administered drugs, the safety, efficacy, and targeting ability requirements have grown as disease treatment research advances. It is difficult to obtain prominent efficacy of traditional drugs simply via oral administration. Numerous studies have demonstrated that cyclodextrins (CDs) can improve the clinical applications of certain orally administered drugs by enhancing their water solubility and masking undesirable odors. Additionally, deeper studies have discovered that CDs can influence disease treatment by altering the drug pharmacokinetics (PK) or pharmacodynamics (PD). This review highlights recent research progress on the PK and PD effects of CD-based oral drug delivery in disease therapy. Firstly, the review describes the characteristics of current drug delivery modes in oral administration. Besides, we minutely summarized the different CD-containing drugs, focusing on the impact of CD-based alterations in PK or PD of orally administered drugs in treating diseases. Finally, we deeply discussed current challenges and future opportunities with regard to PK and PD of CD-based oral drug delivery formulations.

Safety evaluation of the food enzyme α-cyclodextrin glucanotransferase from Escherichia coli strain WCM105xpCM703

The food enzyme α‐cyclodextrin glucanotransferase ((1→4)‐α‐d‐glucan 4‐α‐d‐[(1→4)‐α‐d‐glucano]‐transferase; EC 2.4.1.19) is produced with a genetically modified Escherichia coli strain WCM105xpCM703 by Wacker Chemie GmbH. The production strain harbours a self‐replicating multicopy plasmid which contains genes conferring resistance to two highly important antimicrobials for human and veterinary medicine. The food enzyme is free from viable cells of the production organism, but not of its recombinant DNA. Therefore, the food enzyme poses a risk of promoting the spread of antimicrobial resistance genes. It is intended to be used in starch processing for the production of α‐cyclodextrin. Residual amounts of total organic solids (TOS) are removed by the purification steps applied during the production of α‐cyclodextrin; consequently, dietary exposure was not calculated. Genotoxicity tests, although not raising a safety concern, did not comply with the EFSA guideline. The systemic toxicity was assessed by means of a repeated dose 90‐day oral toxicity study in rats. The study was not supplied as a full report. The Panel identified the highest dose tested as the No Observed Adverse Effect Level, which according to the authors of the study corresponds to 260 mg TOS/kg body weight per day. In the absence of information about the sequence homology of this α‐cyclodextrin glucanotransferase with known allergens, the Panel could not complete the assessment on the allergenicity of the food enzyme. The Panel concludes that the food enzyme α‐cyclodextrin glucanotransferase produced with the genetically modified E. coli strain WCM105xpCM703 cannot be considered safe.

Genetic and rat toxicity studies of cyclodextrin glucanotransferase

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Bacterial cyclodextrin glucanotransferase (CGTase) is used to produce a water soluble form of glycosylated isoquercitrin.

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Genotoxicity battery on CGTase and sodium sulfate negative for mutations and DNA damage.

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No evidence of systemic toxicity in 90-day rat toxicity study of CGTase.

Introduction

Microbiologically derived cyclodextrin glucanotransferase (CGTase) is used commercially as a processing agent in manufacture of food, pharmaceuticals, and cosmetics. Its toxic potential was evaluated in anticipation of use in the production of alpha-glycosyl isoquercitrin, a water-soluble form of quercetin.

Methods

Following OECD guidelines, CGTase, produced by Bacillus pseudalcaliphilus DK-1139, was evaluated in a genotoxicity battery consisting of a bacterial reverse mutation assay, an in vitro micronucleus (MN) assay and MN and comet assays using B6C3F1 male and female mice. These same genotoxicity assays were also conducted for sodium sulfate, a contaminant of CGTase preparation. In a 90-day Sprague Dawley rat toxicity study, CGTase was administered by gavage in water at daily doses of 0, 250, 500, and 1000 mg/kg/day.

Results

CGTase did not induce mutations with or without metabolic activation in the bacterial reverse mutation assay. Formation of micronuclei was not induced in either in vitro or in vivo MN assays with or without metabolic activation. No induction of DNA damage was detected in male or female mouse liver, stomach, or duodenum in the comet assay. Sodium sulfate also tested negative in these same genotoxicity assays. In the 90-day repeated dose rat study there were no treatment-related adverse clinical or pathological findings.

Conclusion

The genotoxicity assays and repeated dose toxicity study support the safe use of CGTase in production of alpha-glycosyl isoquercitrin.

Enhanced production of α-cyclodextrin glycosyltransferase in Escherichia coli by systematic codon usage optimization

Enhancing the production of α-cyclodextrin glycosyltransferase (α-CGTase) is a key aim in α-CGTase industries. Here, the mature α-cgt gene from Paenibacillus macerans JFB05-01 was redesigned with systematic codon optimization to preferentially match codon frequencies of Escherichia coli without altering the amino acid sequence. Following synthesis, codon-optimized α-cgt (coα-cgt) and wild-type α-cgt (wtα-cgt) genes were cloned into pET-20b(+) and expressed in E. coli BL21(DE3). The total protein yield of the synthetic gene was greater than wtα-cgt expression (1,710 mg L−1) by 2,520 mg L−1, with the extracellular enzyme activity being improved to 55.3 U mL−1 in flask fermentation. ΔG values at -3 to +50 of the pelB site of both genes were −19.10 kcal mol−1. Functionally, coα-CGTase was equally as effective as wtα-CGTase in forming α-cyclodextrin (α-CD). These findings suggest that preferred codon usage is advantageous for translational efficiency to increase protein expression. Finally, batch fermentation was applied, and the extracellular coα-CGTase enzyme activity was 326 % that of wtα-CGTase. The results suggest that codon optimization is a reasonable strategy to improve the yield of α-CGTase for industrial application.

Extracellular expression and biochemical characterization of alpha-cyclodextrin glycosyltransferase from Paenibacillus macerans

The cgt gene encoding alpha-cyclodextrin glycosyltransferase (alpha-CGTase) from Paenibacillus macerans strain JFB05-01 was expressed in Escherichia coli as a C-terminal His-tagged protein. After 90h of induction, the activity of alpha-CGTase in the culture medium reached 22.5 U/mL, which was approximately 42-fold higher than that from the parent strain. The recombinant alpha-CGTase was purified to homogeneity through either nickel affinity chromatography or a combination of ion-exchange and hydrophobic interaction chromatography. Then, the purified enzyme was characterized in detail with respect to its cyclization activity. It is a monomer in solution. Its optimum reaction temperature is 45 degrees C, and half-lives are approximately 8h at 40 degrees C, 1.25h at 45 degrees C and 0.5h at 50 degrees C. The recombinant alpha-CGTase has an optimum pH of 5.5 with broad pH stability between pH 6 and 9.5. It is activated by Ca(2+), Ba(2+), and Zn(2+) in a concentration-dependent manner, while it is dramatically inhibited by Hg(2+). The kinetics of the alpha-CGTase-catalyzed cyclization reaction could be fairly well described by the Hill equation.

Safety evaluation of 1,4-alpha-glucan branching enzymes from Bacillus stearothermophilus and Aquifex aeolicus expressed in Bacillus subtilis

1,4-alpha-Glucan branching enzyme (BE; EC 2.4.1.18) is a key biocatalyst in the synthesis of polysaccharides, and is therefore useful in the production of food ingredients. The BEs evaluated in this study (BE-01 and BE-02) are obtained by fermentation of Bacillus subtilis expressing the BE gene from either Bacillus stearothermophilus strain TRBE14 or Aquifex aeolicus strain VF5. The safety of BE-01 and BE-02 have not been previously evaluated, and therefore, both were subjected to standard toxicological testing. In a battery of standard Salmonella typhimurium strains (TA98, TA100, TA1535, and TA1537) and in Escherichia coli WP2uvrA, both with and without metabolic activation, neither BE-01 nor BE-02 exhibited mutagenic activity. Similarly, neither was associated with clastogenic properties in Chinese hamster ovary cells in an in vitro chromosomal aberration assay. In rats, oral administration of BE-01 or BE-02 at doses of up to 15 mL/kg body weight/day (approximately 870 and 900 mg/kg body weight/day, respectively) for 13 weeks did not produce compound-related clinical signs or toxicity, changes in body weight gain, food consumption, hematology, clinical chemistry, urinalysis, organ weights, or in any gross and microscopic findings. The results of this study support the safety of BE-01 and BE-02 in food production.