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Relevance of Catalytic Anti-VIP Antibodies to the Airway
Published in Sami I. Said, Proinflammatory and Antiinflammatory Peptides, 2020
Different proteolytic antibodies and antibody L chains show considerable variation in their catalytic properties. The range of turnover number observed using available recombinant antibody fragments varies from 0.003/min to 2.1/min. The half-life of IgG in blood is about 20 days, which corresponds to cleavage of 86 molecules and 60,480 molecules per molecule of the IgG with turnovers of 0.003 and 2.1/min, respectively. It can be readily seen, therefore, that even at excess substrate concentration, at which only the turnover number determines the rate of catalysis, the proteolytic antibodies are likely to express considerably more potent VIP-neutralizing activity than stoichiometric, reversibly binding molecules. It is worth noting that the antibodies cited here were identified based on their antigen-binding affinity, a procedure that favors tight binding to the antigen ground state, but is unlikely to select catalysts with the best turnover. A strong case can be made that higher-turnover antibodies will be found by applying direct screening assays for catalysis.
Psychosocial Stressors at Work and Stress Prevention Methods among Medical Staff of Psychiatric and Addiction Treatment Wards
Published in Dorota Żołnierczyk-Zreda, Emotional Labour in Work with Patients and Clients, 2020
Equally, workplace health promotion should encompass periodic evaluation of the implemented programs’ effectiveness and impact by conducting employee surveys, and monitoring the accident rate, employee turnover, number of sick leaves, and performance. Such an analysis results should be communicated to the company’s staff, and the management should be obliged to continuously improve the workplace health-promotion methods.
Cholinergic Agonists
Published in Sahab Uddin, Rashid Mamunur, Advances in Neuropharmacology, 2020
Rupali Patil, Aman Upaganlawar
AChE and BuChE both belong to the class of serine hydrolases, which includes many proteases, such as trypsin. Two different regions are available on active site of AChE: an anionic site containing glutamate residue binding with choline moiety of ACh and a catalytic esteratic site. An acetylated enzyme and free choline are formed after the transfer of acetyl group of ACh to serine hydroxyl group. Serine acetyl group gets spontaneously hydrolyzed rapidly. The overall turnover number of AChE is extremely high. A single active site hydrolyzes more than 10,000 molecules of ACh per second (Rang et al., 2011).
Ameliorative effect of gallic acid on cisplatin-induced ovarian toxicity in rats
Published in Drug and Chemical Toxicology, 2023
Elif Ayazoglu Demir, Ahmet Mentese, Ayten Livaoglu, Nihal Turkmen Alemdar, Selim Demir
Chemotherapeutic agents are known to have pro-oxidant characters, generating ROS resulting in depletion of cellular antioxidant power (Olayinka et al.2015). Antioxidant enzymes form the primary line of defense in organisms by converting the ROS into harmless products and protect cells from oxidative damage. Among the antioxidant enzymes, CAT plays a central role in the detoxification of free radicals. CAT is the enzyme with the highest turnover number in the human body and is responsible for the reduction of hydrogen peroxide to water (Olayinka et al.2015, Shergojri et al.2018). The present study has demonstrated that the levels of CAT were lower in CDDP-treated group compared to the control group, while treatments with GA significantly increased the levels of CAT. The reduction of CAT levels by CDDP in this study is an indication that ovarian tissue has become more susceptible to free radical damage. GA was previously reported to protect various tissues (liver and heart) against oxidative stress induced by different chemotherapeutics, including cyclophosphamide, doxorubicin and CDDP through increasing the levels of CAT (Olayinka et al.2015, Omóbòwálé et al.2018, Shergojri et al.2018).
In the quest for new targets for pathogen eradication: the adenylosuccinate synthetase from the bacterium Helicobacter pylori
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2018
Ante Bubić, Natalia Mrnjavac, Igor Stuparević, Marta Łyczek, Beata Wielgus-Kutrowska, Agnieszka Bzowska, Marija Luić, Ivana Leščić Ašler
Kinetic constants determined for all three substrates of AdSS, IMP, GTP, and Asp are given in Table 3. For each substrate, the curve of initial velocity over substrate concentration follows Michaelis–Menten kinetics (Equation (1)). When comparing Michaelis constants of H. pylori AdSS with those of other organisms, it can be observed that they are similar to those of e.g. E. coli AdSS (GTP: 10–48 µM, IMP: 20–200 µM, and Asp: 260–350 µM) or mouse basic isozyme (GTP: 12 µM, IMP: 45 µM, and Asp: 140 µM), while e.g. the mouse acidic isozyme (GTP: 15 µM, IMP: 12 µM, and Asp: 950 µM) or P. falciparum AdSS (GTP: 18 µM, IMP: 23 µM, and Asp: 1800 µM) have significantly higher values of Km for Asp1,39. Turnover number (kcat) of 1 s−1 compares well with kcat for E. coli and P. falciparum AdSS enzymes, however, both mouse enzymes have 4- to 5-fold higher efficacy39. This low value of kcat makes AdSS one of the least efficient enzymes described in the literature, and for E. coli the AdSS reaction is near the rate-limiting step in the bacterium’s growth and reproduction cycle3. This is in line with the known fact that purine metabolism is the growth-limiting step for all cells, both prokaryotic and eukaryotic24.
Evaluation of the paraoxonase-1 kinetic parameters of the lactonase activity by nonlinear fit of progress curves
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2020
Although basic biochemical and physiological principles dictate that it is the activity of a given enzyme that is important with respect to its function, two kinetic parameters determine the activity of enzyme at given substrate concentration; i.e. limiting rate Vmax (=kcat·[E]T) which depends on turnover number and enzyme active sites concentration, and the Michaelis constant Km which is not concentration dependent characteristics of an enzyme. However, the values of Km are associated with polymorfic forms2, enyzme modifications and its environment.