[Changes in physicochemical properties of proteins, caused by modification with alkylhydroxybenzenes].

Kinetic characteristics of model enzymes and physicochemical properties of globular proteins modified by chemical analogues of low-molecular-weight microbial autoregulators (alkylhydroxybenzenes, AHBs) have been studied. C7 and C12 AHB homologues were used, differing in the length of the alkyl radical and the capacity for weak physicochemical interactions. Both homologues affected the degree of protein swelling, viscosity, and the degree of hydrophobicity. The effects depended on the structure of AHBs, their concentration, and pH of the solution, which likely reflects changes in the charge of the protein globule and its solvate cover. Variations of hydrophobicity indices of AHB-modified enzymes (trypsin and lysozyme) were coupled to changes in the catalytic activity. The values of K(M), measured for the enzymes within both AHB complexes, did not change, whereas V(max) increased (in the case of C7 complexes) or decreased (C12 complexes). Possible molecular mechanisms of changes in the physicochemical and catalytic parameters of enzymatically active proteins, induced by modification with structurally distinct AHBs, are described, with emphasis on targeted regulation of functional activity.

[Autoregulation of stress response in microorganisms].

Examples are considered of the involvement of low-molecular-weight autoregulators in the development of resistance of proliferating microbial cultures to unfavorable environmental impacts of various intensity, including impacts programmed to occur in the developmental cycle ("new medium stress," starvation stress) and nonprogrammed impacts. It was shown that extracellular adaptation factors control the reversible adhesion of cells in submerged cultures and the processes of cell reactivation in the poststress period and are involved in the stabilization of cellular biopolymers (proteins and DNA) and subcellular structures (membranes); the adaptogens of the phenolic type also act as efficient scavengers of reactive oxygen species. The protective effect of the adaptogenic autoregulators is manifested in the increase of resistance of microbial cells to stressors of various nature and in the preservation of the cell proliferative capacity.

[The role of alkylhydroxybenzenes in the adaptation of Micrococcus luteus to heat shock].

The response of the gram-positive bacterium Micrococcus luteus to heat shock (45 degrees C, 15 min) and the adaptogenic activity of alkylhydroxybenzenes (AHB), which are extracellular growth-regulating substances of these bacteria, were studied. The perception of stress and the postshock behavior of M. luteus cells proved to depend on the growth phase and medium. The magnitude of stress response was more pronounced in cultures grown on synthetic medium than in cultures grown on rich medium (nutrient broth). During exponential or linear growth, the cells were more sensitive to the temperature effect than during decelerated growth. In linearly growing M. luteus cultures, the amount of total intra- and extracellular alkylhydroxybenzenes, the anabiosis inducers, increased in response to heat shock. AHB redistribution between cells and culture liquid occurred in the course of stress and after stress. In micrococci exposed to heat shock, an increase in the AHB concentration both in cells and culture liquid is likely a defense reaction of stress resistance. This conclusion was confirmed in the experiments with the addition 30 min before the heat shock of a chemical analogue of the anabiosis inducer, C7-AHB (12 mM), which protected M. luteus cells so that their intense growth was observed after shock without any lag. The protective effect of AHB is a result of their ability to form complexes with enzyme macromolecules and stabilize them. The data obtained extend the knowledge of the stress-protective functions of low-molecular-weight autoregulators and of the role of intercellular communications in the stress response of bacterial cultures.

[Protection of Saccharomyces cerevisiae against oxidative and radiation-caused damage by alkyl hydroxybenzenes]. / Zashchita Saccharomyces cerevisiae alkiloksibenzolami ot okislitel'nogo i radiatsionnogo porazheniia.

The effects of C7-alkylhydroxybenzene (C7-AHB) and p-hydroxyethylphenol (tyrosol), chemical analogs of microbial anabiosis autoregulators, on the viability of yeast cells under oxidative stress were investigated. The stress was caused by reactive oxygen species (ROS) produced under gamma irradiation of cell suspensions using doses of 10-150 krad at an intensity of 194 rad/s or by singlet oxygen generated in cells photosensibilized with chlorin e6 (10 micrograms/l). C7-AHB was found to exert a protective effect. The addition of 0.05-0.16 vol% of C7-AHB to cell suspensions 30 min before irradiation protected yeast cells from gamma radiation (50 krad). The protective effect of C7-AHB manifested itself both in the preservation of cell viability during irradiation and in the recovery of their capacity to proliferate after irradiation. In our studies on photodynamic cell inactivation, the fact that the phenolic antioxidant C7-AHB protects cells from intracellular singlet oxygen was revealed for the first time. The analysis of difference absorption spectra of oxidized derivatives of C7-AHB demonstrated that the protective mechanism of C7-AHB involves the scavenging of ROS resulting from oxidative stress. The fact that tyrosol failed to perform a photoprotective function suggests that the antioxidant properties of microbial C7-AHB are not related to their chaperon functions. The results obtained make an important addition to the spectrum of known antioxidant and antistress effects of phenolic compounds.

[Effect of alkylbenzenes on malting processes]. / Vliianie alkiloksibenzolov na protsessy solodorashcheniia.

It has been shown that one of alkyl hydroxybenzenes, C7-AHB, can be used in malting for regulating barley growth. Depending on concentration (0.01-1.0%) and duration (10 min to 6 h), treatment of barley with a C7-AHB solution stimulates embryo development (0.01-0.02%) or suppresses the growth of vegetative organs (> 0.5%) and modulates enzyme activities in germinating grains. Stimulation of the activities of the amylolytic and protein-proteinase complexes in barley depending on C7-AHB concentration improves malt quality by increasing both the degree of its saccharification and protein dissolution.

[Involvement of microbial alkyl hydroxybenzenes in the regulation of autolytic degradation of yeast cells]. / Uchastie mikgobnykh alkiloksibenzolov v reguliatsii avtoliticheskoi destruktsii drozhzhevykh kletok.

A comparative study was performed of the processes of autolytic degradation of the cells of Saccharomyces cerevisiae and Schizosaccharomyces pombe under conditions simulating the phase of cell death in microbial cultures: (1) during autolysis induced by oleic acid, which is the chemical analogue of factors d2 (autolysis autoinducer), (2) under the effect of extracellular microbial proteinases (enzymatic lysis), and (3) under concomitant effect of the enzymes of the endogenous autolytic complex and exogenous proteinases (heterolysis). Regulatory mechanisms controlling the rate and profundity of autolysis were elucidated, relying on the stabilization of hydrolytic enzymes and enhancement of their activity in their complexes with a chemical analogue of microbial autoregulatory factors d1, which belong to alkylhydroxybenzenes and fulfil functions of chemical chaperons. The changes in the activity of proteinases and enzymes of the autolytic complex were shown to be dependent on the concentration of the analogue at the moment of complex formation.