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Within the alpha/beta hydrolase fold superfamily of proteins, the COesterase group (carboxylesterase type B, block C, cholinesterases…) diverged from the other groups through addition of an N-terminal disulfide bond and simultaneous increase in the mean size of the protein (1). This disulfide bond creates a large loop, which is essential for the high catalytic activity of cholinesterases through formation of the upper part of the active center gorge. In some non-catalytic members of the family, the loop may be necessary for heterologous partner recognition. The shuffling of this portion of protein occurred at the time of emergence of the fungi/metazoan lineage. Homologous proteins with this N-terminal disulfide bond are absent in plants but they are found in a limited number of bacterial genomes. In prokaryotes, the genes coding for such homologous enzymes may have been acquired by horizontal transfer. However the cysteines of the first disulfide bond are often lost in bacteria. Natural expression in bacteria of CO-esterases comprising this disulfide bond may have required compensatory mutations or expression of new chaperones. This disulfide bond may also challenge expression of the eukaryote-specific cholinesterases in E. coli. Recently , catalytically active human acetylcholinesterase and butyrylcholinesterase were successfully expressed in E. coli. The key was the use of a peptidic sequence optimized through the Protein Repair One Stop Shop process, an automated structure- and sequence-based algorithm toward expression of properly folded, soluble eukaryotic proteins with an enhanced stability (2,3). Surprisingly however, the crystal structure of the optimized butyrylcholinesterase variant expressed from bacteria revealed co-existing ‘close’ and ‘open’ states of the first disulfide bond. Whether the ‘open bond’ involves two cysteines (i.e., the bond never formed) or two half-cystines (i.e., the bond properly formed, then broke during the production/analysis process) cannot be inferred from the structural data. Yet, this observation suggests that this first bond is difficult to maintain in E. coli-expressed cholinesterases.

The paper deals with industrial chemical safety with a focus on major chemical accidents, hazardous chemicals and mixtures with emphasis on the dangers of selected sub-limit sources of risk. Currently, the two main laws in force, the Major Accident Prevention Act of 2015 (1), or the so-called "Chemicals Act" or the Chemicals and Mixtures Act of 2011 (2), have failed to address the serious safety issues of the so-called "Sub-threshold sources of risk" consisting of the low masses of hazardous chemicals.
Until 2017, there was no clearly defined professional methodology, procedure or other tool to assess risk assessment of sources with hazardous chemicals and mixtures.
The main part briefly mentions the instruction of the General Director of the Fire and Rescue Service of the Czech Republic (Instruction 35/2017 (3)), which solves the issue very well and provides professional and methodological instructions for capturing and evaluating sub-limit sources of risk. This clearly improves the prevention of these events, it also increases the preparedness for possible emergency releases of hazardous substances and, last but not least, it can also increase the preparedness of the population for the correct response to releases of below-limit amounts of certain hazardous substances.

Enrofloxacin and marbofloxacin are two veterinary fluoroquinolones used to treat severe bacterial infections. The release of fluoroquinolones in the environment is mainly due to the direct discharge of aquaculture products and the excretion in urine and feces of livestock animals. It results in the contamination of soil, surface water, sediment, ground water and biota.
We focused on acute and reproductive effects of enrofloxacin and marbofloxacin, in particular. Assessment of the impact of selected antibiotics on important representatives of the aquatic environment. The aim of this study was to investigate the chronic toxicity of the antibiotics to Daphnia magna and Tubifex tubifex. Selected representatives are an important part of the fish food chain. The effect was tested on the growth and reproduction of D. magna in a chronic test scenario according to OECD guidelines 211. Tests with Tubifex tubifex were performed according to method ASTM E1706-04. We also performed an acute toxicity test with Danio rerio. The experiment was performed according to the Guideline for Test No. 236: Fish Embryo Acute Toxicity (OECD 2013). We observed mortality, malformation, hatching rate and heartbeat.  Graphpad Prism was used for data visualization and statistics. Dose-response curves were constructed and EC50 values were calculated. In particular, changes in the behaviour of test organisms were noted.

Phytic acid (IP6) is the most abundant inositol phosphate in nature present in plants as well as in mammalian cells, thus, IP6 is common part of human diet. IP6 has been considered for a long time as an antinutritional component due to its ability to bound minerals and affect their bioavailability in gastrointestinal tract (1). On the other hand, the protective effects of IP6 have been reported in pathological conditions including neurodegenerative diseases, cardiovascular diseases and cancer, likewise, a hepatoprotective effect has been observed (2). Cytochromes P450 (CYPs) are key enzymes involved in the metabolism of 70-80% of all clinically used drugs and they are responsible for variability in drug response. Expression of CYPs is affected by many factors and can be regulated by specific nuclear receptors such as aryl hydrocarbon receptor (AhR) and pregnane X receptor (PXR). To date, variety of diet-derived metabolites, have been identified as ligands of these receptors showing that different diet habits may contribute to interindividual differences in CYP activity.
In our study, the effect of IP6 on CYPs expression and enzymatic activity was assessed using different hepatic cell models. We have found that mRNA expression of CYP2B6, CYP2E1 and CYP3A4 was significantly downregulated by 10μM IP6 in primary human hepatocytes.
Therefore, further studies are needed to evaluate the complex functions of IP6 and its possible interaction with drug metabolism in order to translate its promising therapeutic potential to clinical practice.