Effect of organic additives on storage stability of camel liver catalase against environmental conditions

The storage stability of catalase is very low under practical reaction conditions. Therefore, this study is aimed to evaluate the storage stability of catalase from camel liver by treated it with polyethylene glycol (PEG), glycerol, bovine serum albumin (BSA) and glucose against different storage conditions. The effect of some additives as stabilizers on the storage stability of camel liver catalase at 4°C and 30°C after 30 and 90 days was studied. The enzyme with additives at 5%concentration was more stable at 4 and 30°C for 90 days of incubation than native enzyme. The activity of catalase was more thermal stable in presence of 5%additive. The activity of enzyme with 5%BSA and glucose was retained 60%of its activity at 60°C. At pH 11 the catalase with glucose retained 30%of its activity. The native enzyme lost 80%of its activity in presence of 5 mM β-mercaptoethanol, where the enzyme with additive retained 30–46%of its activity. At 8 M urea, the native enzyme and enzyme with 5%of all additives retained 28%and 61–77%of its activity, respectively. The catalase with additives retained 50–90%of its activity in presence of different dyes. The results appeared that the catalase with additives may be used for elimination of excess of hydrogen peroxide after bleaching of textile.

The High-Spin Heme bL Mutant Exposes Dominant Reaction Leading to the Formation of the Semiquinone Spin-Coupled to the [2Fe-2S]+ Cluster at the Qo Site of Rhodobacter capsulatus Cytochrome bc1

Cytochrome bc1 (mitochondrial complex III) catalyzes electron transfer from quinols to cytochrome c and couples this reaction with proton translocation across lipid membrane; thus, it contributes to the generation of protonmotive force used for the synthesis of ATP. The energetic efficiency of the enzyme relies on a bifurcation reaction taking place at the Qo site which upon oxidation of ubiquinol directs one electron to the Rieske 2Fe2S cluster and the other to heme bL. The molecular mechanism of this reaction remains unclear. A semiquinone spin-coupled to the reduced 2Fe2S cluster (SQo-2Fe2S) was identified as a state associated with the operation of the Qo site. To get insights into the mechanism of the formation of this state, we first constructed a mutant in which one of the histidine ligands of the iron ion of heme bLRhodobacter capsulatus cytochrome bc1 was replaced by asparagine (H198N). This converted the low-spin, low-potential heme into the high-spin, high-potential species which is unable to support enzymatic turnover. We performed a comparative analysis of redox titrations of antimycin-supplemented bacterial photosynthetic membranes containing native enzyme and the mutant. The titrations revealed that H198N failed to generate detectable amounts of SQo-2Fe2S under neither equilibrium (in dark) nor nonequilibrium (in light), whereas the native enzyme generated clearly detectable SQo-2Fe2S in light. This provided further support for the mechanism in which the back electron transfer from heme bL to a ubiquinone bound at the Qo site is mainly responsible for the formation of semiquinone trapped in the SQo-2Fe2S state in R. capusulatus cytochrome bc1.

Preparation of Catalase Cross-Linked Aggregates Based on Vaterite Matrix

A new technique has been developed for the synthesis of cross-linked catalase aggregates by treatment of the enzyme incorporated into the pores of vaterite microspheres with glutaraldehyde and subsequent dissolving of the inorganic matrix. The resulting aggregates have a spherical shape, a narrow particle size distribution and a high specific activity of the enzyme. The number and enzymatic activity of the cross-linked aggregates strongly depends on the rate of the matrix dissolution: mild dissolution conditions made it possible to increase the number of formed protein particles, the residual specific catalase activity of which is only 2 times less than that of the native enzyme. The storage stability of the cross-linked aggregates is comparable to that of the native enzyme of the same concentration. Key words: vaterite, glutaraldehyde, immobilized preparations, intermolecular cross-linking, co-precipitation, CLEAs. Acknowledgment - The authors are grateful to the staff of the M.V. Lomonosov Moscow State University A.N. Prusov for help in obtaining TEM images and A.A. Tatarintseva for assistance in obtaining SEM images. Funding - This work was supported in part by Lomonosov Moscow State University (Registration Theme АААА-А21-121011290089-4). The authors also acknowledge Lomonosov Moscow State University Development Program PNR 5.13.

Effect of Conjugation of Activated Glutaraldehyde-Nanochitosan with L-Asparaginase as an Anti Cancer Enzyme on its Stability and Physicochemical Properties

Introduction: The bacterial Asparaginase is used in the treatment of asparagine-dependent tumors, particularly lymphatic sarcoma and acute lymphoblastic leukemia. However, the instability of the enzyme increases the number of injections that are accompanied by high immune responses. The aim of this study was to investigate the conjugation of L-asparaginase with nanochitosan glutaraldehyde (NCG) derivative and its effect on the physichochemical properties of conjugated enzyme. Methods: In this experimental study, nanochitosan was synthesized using reduction method with acetic acid and its physicochemical properties were evaluated using transmission electron microscopy and particle size analyzer. Activated NCG derivative was produced using 3% acetic acid. The conjugation of NCG derivative to L-asparaginase was performed with different molar ratios of enzyme/nanochitosan (1:2, 1:5, 1:10 and 1:20) in the presence of sodium cyano borohydrate; and the ratio with the highest residual activity was used for physicochemical evaluation. The activity of enzyme at different temperatures and pH, its half-life and stability after freezing and resistance to proteolysis were analyzed through repeated measure analysis of variance using SPSS 18 software. Results: The results of this study showed that the conjugation of L-asparaginase with NCG derivative resulted in maintaining the 70% enzyme activity. The activity of conjugated enzyme was higher than native enzyme after freezing and trypsin treatment. The optimum pH and temperature of conjugated enzyme did not change, while it had higher activity in wide range of pH and temperature compared with native enzyme. Conclusion: Conjugation of L-asparaginase with NCG derivative improved physicochemical and stability of enzyme and this method can be used for production of improved L-asparaginase for clinical application.

SARS-CoV-2 Main Protease: A Molecular Dynamic Study

We provide results from a molecular dynamics simulation of the SARS-CoV-2 main protease in the monomer and dimer states of the native enzyme and also bound to a peptide substrate.<br>

Helicobacter pylori infection impairs chaperone-assisted maturation of Na-K-ATPase in gastric epithelium

This work provides evidence that Helicobacter pylori decreases levels of Na-K-ATPase, a vital transport enzyme, in gastric epithelia, both in acutely infected cultured cells and in chronically infected patients and animals. The bacteria interfere with BiP-assisted folding of newly-made Na-K-ATPase subunits in the endoplasmic reticulum, accelerating their ubiquitylation and proteasomal degradation and decreasing efficiency of the assembly of native enzyme. Decreased Na-K-ATPase expression contributes to H. pylori-induced gastric injury.

Graphene oxide flake activation via divinylsulfone – a procedure for efficient β-galactosidase immobilization

Flaky graphene oxide was activated with divinylsulfone followed by immobilization of the β-galactosidase enzyme. An active and stable preparation was obtained. β-galactosidase stability after immobilization was much higher than with the native enzyme. The half-life time of the immobilized enzyme was estimated as 165 hours, while for the native form, the estimate was only 5 hours. The developed procedure for the preparation of flaked graphene and its use in the chemical immobilization of enzymes can be used for any enzyme. A processing solution for continuous operation was proposed and verified using cow’s milk, with lactose as the hydrolysed substrate, as a dosing stream. Lactose, a milk sugar, was effectively hydrolysed. Product for allergy sufferers who cannot digest lactose has been obtained in this way.