Tag Archives: superoxide anion

Spin-orbit coupling effects in O(2) activation by cofactor-independent 2,4-dioxygenase

B. F. Minaev1, R. R. Valiev2

1Bohdan Khmelnytsky National University of Cherkasy, Ukraine;
e-mail: bfmin43@ukr.net;
2Royal Institute of Technology, Stockholm, Sweden;
e-mail: valievrashid@mail.ru

Received: 22 August 2018; Accepted: 13 December 2018

The O2 (dioxygen) is paramagnetic molecule with two non-paired electron spins and triplet ground state (S = 1) while majority of organic molecules are diamagnetic species; they have all electron spins paired and the singlet ground state with the total spin S = 0. Oxygenases catalyze a concerted insertion of the triplet dioxygen into organic (diamagnetic) molecules in a strictly spin-forbidden process and this puzzle is not solved so far in modern enzymology. Many oxidases and oxygenases utilize the π-conjugated organic cofactor (like flavins, pterins) in a singlet ground state and reaction of cofactor with O2 is still spin-forbidden. It is clear that the protein environment in the enzyme active-site “helps” in some way to overcome spin prohibition, but this environment is definitely diamagnetic and the spin-puzzle still exists. Some oxidases and oxygenases use paramagnetic metal ions as a cofactor; in this case the spin prohibition is formally reduced. In recent years, a numbers of oxidative enzymes are discovered which do not contain any cofactor. In the present work, we considered a rather popular cofactor-free bacterial 2,4-dioxygenase and its oxygenolytic reactions with 2-n-alkyl-3-hydroxy-4(1H)-quinolones (AHQ’s). We presented results of quantum-chemical calculations of intermediate diradical proposed recently for direct reaction of dioxygen with AHQ substrate and made conclusion about the mechanism of spin-catalysis.

Stress-responsive systems in rat pancreas upon long-term gastric hypochlorhydria and administration of multiprobiotic “Symbiter®”

K. O. Dvorshchenko, S. Ye. Vakal, A. S. Dranitsina, S. A. Senin, L. I. Ostapchenko

Taras Shevchenko National University of Kyiv, Ukraine;
e-mail: k21037@gmail.com

The intensity of free-radical processes upon long-term omeprazole-induced hypoacidity in the rat pancreas was investigated. Significant violation of oxidative-antioxidative balance in pancreatic tissue upon gastric hypochlorhydria was established: overproduction of superoxide anion, quantitative changes of lipid functional groups, increased level of lipid peroxidation products, augmentation of xanthine oxidase, superoxide dismutase and glutathione transferase activity, as well as depletion of catalase, glutathione peroxidase activity and reduced glutathione content. The inflected expression of Cckbr gene in the rat pancreas upon these conditions was also observed, thus suggesting an increased risk of pathological changes development in the gland. Abovementioned parameters were only partially restored to control values in the case of simultaneous administration of multiprobiotic “Symbiter®” with omeprazole, thus indicating the ability of this preparation to efficiently counteract the development of oxidative damages in pancrea­tic tissues upon long-term hypoacidic conditions.