Volume 81, Nº 8 (2016)

ß-Propeller phytases of Bacillus are unique highly conservative and highly specific enzymes capable of cleaving insoluble phytate compounds. In this review, we analyzed data on the properties of these enzymes, their differences from other phytases, and their unique spatial structures and substrate specificities. We considered influences of different factors on the catalytic activity and thermostability of these enzymes. There are few data on the hydrolysis mechanism of these enzymes, which makes it difficult to analyze their mechanism of action and their final products. We analyzed the available data on hydrolysis by ß-propeller phytases of calcium complexes with myo-inositol hexakisphosphate.

The widespread occurrence of malignant tumors motivates great attention to finding and investigating effective new antitumor preparations. Such preparations include compounds of the vitamin E family. Among them, α-tocopheryl succinate (vitamin E succinate (VES)) has the most pronounced antitumor properties. In this review, various targets and mechanisms of the antitumor effect of vitamin E succinate are characterized. It has been shown that VES has multiple intracellular targets and effects, and as a result VES is able to induce apoptosis in tumor cells, inhibit their proliferation, induce differentiation, prevent metastasizing, and inhibit angiogenesis. However, VES has minimal effects on normal cells and tissues. Due to the variety of targets and selectivity of action, VES is a promising agent against malignant neoplasms. More detailed studies in this area can contribute to development of effective and safe chemotherapeutic preparations.

Therapeutic monoclonal antibodies (TMA) provide an important means for treating diseases that were previously considered untreatable. Currently more than 40 full-size TMAs created primarily based on immunoglobulin G1 are widely used for treating various illnesses. Glycosylation of TMA is among other numerous factors that affect their biological activity, effector functions, immunogenicity, and half-life in the patient’s serum. The importance of carbohydrate residues for activity of human serum immunoglobulin and TMA produced in animal cells is considered in this review, with emphasis given to N-glycosylation of the Fc fragment of the antibody.

To assess the role of redox state of photosystem II (PSII) acceptor side electron carriers in PSII photochemical activity, we studied sub-millisecond fluorescence kinetics of the wild type Synechocystis PCC 6803 and its mutants with natural variability in the redox state of the plastoquinone (PQ) pool. In cyanobacteria, dark adaptation tends to reduce PQ pool and induce a shift of the cyanobacterial photosynthetic apparatus to State 2, whereas illumination oxidizes PQ pool, leading to State 1 (Mullineaux, C. W., and Holzwarth, A. R. (1990) FEBS Lett., 260, 245-248). We show here that dark-adapted Ox^– mutant with naturally reduced PQ is characterized by slower Q_A^– reoxidation and O₂ evolution rates, as well as lower quantum yield of PSII primary photochemical reactions (F_v/F_m) as compared to the wild type and SDH–mutant, in which the PQ pool remains oxidized in the dark. These results indicate a large portion of photochemically inactive PSII reaction centers in the Ox^– mutant after dark adaptation. While light adaptation increases F_v/F_m in all tested strains, indicating PSII activation, by far the greatest increase in F_v/F_m and O₂ evolution rates is observed in the Ox^– mutant. Continuous illumination of Ox^– mutant cells with low-intensity blue light, that accelerates Q_A^– reoxidation, also increases F_v/F_m and PSII functional absorption cross-section (590 nm); this effect is almost absent in the wild type and SDH–mutant. We believe that these changes are caused by the reorganization of the photosynthetic apparatus during transition from State 2 to State 1. We propose that two processes affect the PSII activity during changes of light conditions: 1) reversible inactivation of PSII, which is associated with the reduction of electron carriers on the PSII acceptor side in the dark, and 2) PSII activation under low light related to the increase in functional absorption cross-section at 590 nm.

Side-by-side with inhibition of the Na⁺,K⁺-ATPase ouabain and other cardiotonic steroids (CTS) can affect cell functions by mechanisms other than regulation of the intracellular Na⁺ and K⁺ ratio ([Na⁺]_i/[K⁺]_i). Thus, we compared the doseand time-dependences of the effect of ouabain on intracellular [Na⁺]_i/[K⁺]_i ratio, Na⁺,K⁺-ATPase activity, and proliferation of human umbilical vein endothelial cells (HUVEC). Treatment of the cells with 1-3 nM ouabain for 24-72 h decreased the [Na⁺]_i/[K⁺]_i ratio and increased cell proliferation by 20-50%. We discovered that the same ouabain concentrations increased Na⁺,K⁺-ATPase activity by 25-30%, as measured by the rate of ⁸⁶Rb⁺ influx. Higher ouabain concentrations inhibited Na⁺,K⁺-ATPase, increased [Na⁺]_i/[K⁺]_i ratio, suppressed cell growth, and caused cell death. When cells were treated with low ouabain concentrations for 48 or 72 h, a negative correlation between [Na⁺]_i/[K⁺]_i ratio and cell growth activation was observed. In cells treated with high ouabain concentrations for 24 h, the [Na⁺]_i/[K⁺]_i ratio correlated positively with proliferation inhibition. These data demonstrate that inhibition of HUVEC proliferation at high CTS concentrations correlates with dissipation of the Na⁺ and K⁺ concentration gradients, whereas cell growth stimulation by low CTS doses results from activation of Na⁺,K⁺-ATPase and decrease in the [Na⁺]_i/[K⁺]_i ratio.

Primary cultures of rat hepatocytes were studied in serum-free media. Ultradian protein synthesis rhythm was used as a marker of cell synchronization in the population. Addition of glutamic acid (0.2 mg/ml) to the medium of nonsynchronous sparse cultures resulted in detection of a common protein synthesis rhythm, hence in synchronization of the cells. The antagonist of glutamic acid metabotropic receptors MCPG (0.01 mg/ml) added together with glutamic acid abolished the synchronization effect; in sparse cultures, no rhythm was detected. Feeding rats with glutamic acid (30 mg with food) resulted in protein synthesis rhythm in sparse cultures obtained from the rats. After feeding without glutamic acid, linear kinetics of protein synthesis was revealed. Thus, glutamic acid, a component of blood as a non-neural transmitter, can synchronize the activity of hepatocytes and can form common rhythm of protein synthesis in vitro and in vivo. This effect is realized via receptors. Mechanisms of cell–cell communication are discussed on analyzing effects of non-neural functions of neurotransmitters. Glutamic acid is used clinically in humans. Hence, a previously unknown function of this drug is revealed.

The dynamics of aging is often described by survival curves that show the proportion of individuals surviving to a given age. The shape of the survival curve reflects the dependence of mortality on age, and it varies greatly for different organisms. In a recently published paper, Stroustrup and coauthors ((2016) Nature, {vn530}, 103–107) showed that many factors affecting the lifespan of Caenorhabditis elegans do not change the shape of the survival curve, but only stretch or compress it in time. Apparently, this means that aging is a programmed process whose trajectory is difficult to change, although it is possible to speed it up or slow it down. More research is needed to clarify whether the “rule of temporal scaling” is applicable to other organisms. A good indicator of temporal scaling is the coefficient of lifespan variation: similar values of this coefficient for two samples indicate similar shape of the survival curves. Preliminary results of experiments on adaptation of Drosophila melanogaster to unfavorable food show that temporal scalability of survival curves is sometimes present in more complex organisms, although this is not a universal rule. Both evolutionary and environmental changes sometimes affect only the average lifespan without changing the coefficient of variation (in this case, temporal scaling is present), but often both parameters (i.e. both scale and shape of the survival curve) change simultaneously. In addition to the relative stability of the coefficient of variation, another possible argument in favor of genetic determination of the aging process is relatively low variability of the time of death, which is sometimes of the same order of magnitude as the variability of timing of other ontogenetic events, such as the onset of sexual maturation.