Analysis of polybrominated diphenyl ether and tetrabromobisphenol A in plastic samples in Mongolia

This study was conducted to determine brominated flame retardants (BFRs) in electronic products in view compliance with the Restriction of Hazardous Substances (RoHS) and initiated by activities for implementation of the Stockholm Convention. Brominated flame retardants (BFRs) are synthetic additives mainly used in electrical and electronic appliances and in construction materials. Total 16 plastic casing samples were tested for threshold levels of polybrominated ethers. According the XFR results, the concentration of cadmium, lead, mercury and chromium were found below than Maximum Concentration Value (MCV) of RoHS, while the concentration of total bromine was exceeded the standard limitations in the samples. Only 1 out of the 16 plastic samples contains DecaBDEs while Tetrabromobisphenol (TBBP-A) is the major brominated flame retardants. However by the presence of one sample the average concentration of DecaBDE was above the RoHS limit of 1000 ppm as found in studies in other countries.DOI: http://doi.dx.org/10.5564/mjc.v15i0.317 Mongolian Journal of Chemistry 15 (41), 2014, p27-3

Utilization of spent brewer’s yeast Saccharomyces cerevisiae for the production of yeast enzymatic hydrolysate

Spent brewer’s yeast (Saccharomyces cerevisiae) is a rich source of protein, vitamins and widely used as a raw material for production of food supplements. The autolysis and enzymatic treatment of spent brewer’s yeast using Pancreatin (2.5%) and Flavourzyme (2.5%) were performed at 45 °C and 50 °C, respectively. The autolysis and hydrolysis processes were evaluated by determining a soluble solids, soluble protein concentration and α-amino nitrogen content in a reaction mixture. The yield of pancreatic digest and α-amino nitrogen content was high in comparison with autolysis and Flavourzyme treatment. The total solids recovery in dry Yeast hydrolysate was about 50%, a protein and α-amino nitrogen content was 55.9 and 4.8%, respectively. These results show the possibility of utilizing the spent brewer’s yeast as hydrolysate using hydrolytic enzymes and use it as a food supplement after biological experiments.DOI: http://dx.doi.org/10.5564/mjc.v12i0.179 Mongolian Journal of Chemistry Vol.12 2011: 88-9

Antioxidant properties of pancreatic hydrolysates from various protein sources

Antioxidant activity of pancreatic hydrolysates of casein, spent brewer’s yeast, bovine liver and tendon was evaluated in comparison to unhydrolised substrates by ABTS assay. In the result of enzymic treatment ABTS cation radical scavenging activity of spent brewer’s yeast, bovine liver and bovine tendon was increased in 4.8, 3.3, and 2.3 times respectively, except casein.  The IC50 values of ABTS cation radical scavenging for casein and it’s hydrolysate were similar. The IC50 values of DPPH radical scavenging activity for pancreatic hydrolysates of casein, spent brewer’s yeast, bovine liver and tendon  were 1.8±0.1 mg/ml,  1.3±0.1 mg/ml, 1.7±0.1 mg/ml, and 6.2±0.1 mg/ml respectively. Above mentioned hydrolysates of various origin were produced at the same conditions (temperature 50oC, pH 7.5-8.9, duration 5 hours) using fresh bovine pancreatic tissue as an enzyme source. The extent of hydrolysis expressed as AN/TN (amino nitrogen/total nitrogen) for hydrolysates had  values from 0.36±0.02 to 0.46±0.04.DOI: http://doi.dx.org/10.5564/mjc.v15i0.321 Mongolian Journal of Chemistry 15 (41), 2014, p43-4

Chemistry-based functional proteomics reveals novel members of the deubiquitinating enzyme family.

The ubiquitin (Ub)-proteasome system includes a large family of deubiquitinating enzymes (DUBs). Many members are assigned to this enzyme class by sequence similarity but without evidence for biological activity. A panel of novel DUB-specific probes was generated by a chemical ligation method. These probes allowed identification of DUBs and associated components by tandem mass spectrometry, as well as rapid demonstration of enzymatic activity for gene products whose functions were inferred from primary structure. We identified 23 active DUBs in EL4 cells, including the tumor suppressor CYLD1. At least two DUBs tightly interact with the proteasome 19S regulatory complex. An OTU domain-containing protein, with no sequence homology to any known DUBs, was isolated. We show that this polypeptide reacts with the C terminus of Ub, thus demonstrating DUB-like enzymatic activity for this novel superfamily of proteases

STABILIZATION OF THE WEATHERED SOILS AND FORMATION OF PERMANENT GRASS GREEN COVER BY CRYOSTRUCTURING

A new chemical-biological method of preventing soil erosion using cryogel in combination with perennial grasses is proposed. The cryogel is shown not to have negative impact on aboriginal soil microflora. On the one hand the cryogel polymer matrix in the soil is strong enough to withstand the effects of erosion but on the other hand it is quite elastic, so it will not hinder plant growth. The seeds germinated through the cryogel layer form a stable green cover. Cryogels are harmless to humans and environmentally friendly

The structure of SENP1–SUMO-2 complex suggests a structural basis for discrimination between SUMO paralogues during processing

The SUMO (small ubiquitin-like modifier)-specific protease SENP1 (sentrin-specific protease 1) can process the three forms of SUMO to their mature forms and deconjugate SUMO from modified substrates. It has been demonstrated previously that SENP1 processed SUMO-1 more efficiently than SUMO-2, but displayed little difference in its ability to deconjugate the different SUMO paralogues from modified substrates. To determine the basis for this substrate specificity, we have determined the crystal structure of SENP1 in isolation and in a transition-state complex with SUMO-2. The interface between SUMO-2 and SENP1 has a relatively poor complementarity, and most of the recognition is determined by interaction between the conserved C-terminus of SUMO-2 and the cleft in the protease. Although SENP1 is rather similar in structure to the related protease SENP2, these proteases have different SUMO-processing activities. Electrostatic analysis of SENP1 in the region where the C-terminal peptide, removed during maturation, would project indicates that it is the electrostatic complementarity between this region of SENP1 and the C-terminal peptides of the various SUMO paralogues that mediates selectivity

SUMO protease SENP1 induces isomerization of the scissile peptide bond

Small ubiquitin-like modifier (SUMO)-specific protease SENP1 processes SUMO-1, SUMO-2 and SUMO-3 to mature forms and deconjugates them from modified proteins. To establish the proteolytic mechanism, we determined structures of catalytically inactive SENP1 bound to SUMO-1-modified RanGAP1 and to unprocessed SUMO-1. In each case, the scissile peptide bond is kinked at a right angle to the C-terminal tail of SUMO-1 and has the cis configuration of the amide nitrogens. SENP1 preferentially processes SUMO-1 over SUMO-2, but binding thermodynamics of full-length SUMO-1 and SUMO-2 to SENP1 and K(m) values for processing are very similar. However, k(cat) values differ by 50-fold. Thus, discrimination between unprocessed SUMO-1 and SUMO-2 by SENP1 is based on a catalytic step rather than substrate binding and is likely to reflect differences in the ability of SENP1 to correctly orientate the scissile bonds in SUMO-1 and SUMO-2

On terminal alkynes that can react with active-site cysteine nucleophiles in proteases

Active-site directed probes are powerful in studies of enzymatic function. We report an active-site directed probe based on a warhead so far considered unreactive. By replacing the C-terminal carboxylate of ubiquitin (Ub) with an alkyne functionality, a selective reaction with the active-site cysteine residue of de-ubiquitinating enzymes was observed. The resulting product was shown to be a quaternary vinyl thioether, as determined by X-ray crystallography. Proteomic analysis of proteins bound to an immobilized Ub alkyne probe confirmed the selectivity toward de-ubiquitinating enzymes. The observed reactivity is not just restricted to propargylated Ub, as highlighted by the selective reaction between caspase-1 (interleukin converting enzyme) and a propargylated peptide derived from IL-1β, a caspase-1 substrate