UDC 582.282.23+575.113+579.222 82 ISSN 2415-3826 (Online), ISSN 2219-3782 (Print). Фактори експериментальної еволюції організмів 2017. Том 21 FEDOROVYCH D.V. 1 , YURKIV M.T. 1 , KOLODII O.M. 1 , KURYLENKO O.O. 1 , GRABEK-LEJKO D. 2 , SIBIRNY A.A. 1,2© 1 Institute of Cell Biology of Nat. Acad. Sci. of Ukraine, Ukraine 79005, Lviv, Drahomanova str., 14/16, е-mail: fedorovych@cellbiol.lviv.ua 2 University of Rzeszow, Poland, 35-959, Rzeszow, Zelwerowicza, 4, e-mail: sibirny@cellbiol.lviv.ua, dorobek@o2.pl  fedorovych@cellbiol.lviv.ua, (050) 371-00-40 THE ROLE OF GLUTATHIONE IN DETOXIFICATION OF CHROMATE BY HANSENULA (OGATAEA) POLYMORPHA YEAST © FEDOROVYCH D.V., YURKIV M.T., KOLODII O.M., KURYLENKO O.O., GRABEK-LEJKO D., SIBIRNY A.A. Glutathione (GSH, г-glutamyl-cysteinyl- glycine) is the most abundant non-protein thiol present at relatively high concentration in most living cells. It is the main reservoir of non-protein sulfur which protects cells from metabolic, oxida- tive and environmental stresses [1–3]. Due to the unique reductive and nuсleophilic properties, GSH plays pivotal role in protecting cells against reactive oxygen species (ROS), xenobiotics and heavy met- als, as well as in detoxification of endogenous toxic metabolites. GSH is the main cellular antioxidant, which can directly react with the reactive oxygen species and take part in detoxification of lipid per- oxidation products, like malondialdehyde and 4- hydroxy-2-nonenal. It is known that GSH is in- volved in homeostasis of different metals in many organisms [3–5]. Microbial detoxification of metal ions is carried out by several mechanisms, which include the regulation of uptake, transformation to less toxic forms and intracellular immobilization [6]. Metal ions that are assimilated by cells generate ROS directly (redox-active metals Cu, Fe, Cr, V) or indirectly by the substitution of redox-active metals in their binding sites (Cd, Hg, Ni, Pb). GSH can directly bind some metal ions in six potential coor- dination sites for their binding. GSH complexes with metals may be generated spontaneously. Such complexes may have various metabolic functions, in particular they can help in metal transport through the cell membrane, be a source of cysteine and as cofactors in redox reactions. The involvement of GSH in metabolism of cadmium, copper, iron is well studied [3–5]. In many organisms GSH is involved in reduction of chromate, which is mutagenic and carcinogenic. Cr 6+ is reduced thus to the less toxic Cr 3+ . This process is accompanied by the generation of ROS, that damage cellular phospholipids, proteins and DNA. Although Сr 6+ can be reduced non- enzymatically, GSH and GSH-dependent enzymes play an important role in the reduction of intracellu- lar chromate. Also essential role in the detoxifica- tion of chromate in yeasts belongs to extracellular reduction of Cr 6+ to Cr 3+ , which forms kinetically inactive complexes with substances of unknown nature [7]. The role of GSH in chromate detoxifica- tion in yeasts is unclear. In the fission yeast Schizosaccharomyces pombe the decreased intra- cellular GSH level leads to increased sensitivity to chromate, and, according to the authors, this sug- gests that GSH may effectively protect cells against chromate toxicity by ROS scavenging [8]. Mutant strain with decreased GSH reductase activity was more resistant to chromate due to reduced genera- tion of hydroxyl radicals by the action of chromate. The introduction of the gene encoding GSH reduc- tase into genome of this mutant caused the loss of resistance to chromate, demonstrating the impor- tance of the GSH reductase-NADPH system in chromate reduction. On the other hand, in the yeast Saccharomyces cerevisiae GSH is not involved in cell tolerance to chromate and other metals. How- ever, reduction of GSH pool in cells led to de- creased chromate adsorption [6]. To evaluate the role of GSH in chromate de- toxification in yeasts we used recombinant strains of Hansenula (Ogataea) polymorpha with overex- pressed GSH2 (coding the first enzyme of GSH biosynthesis, gamma-glutamyl cysteine synthetase) and MET4 (the central regulatory gene of sulfur metabolism) genes, as well as mutant with deleted GSH2 gene. The paper presents data showing that high level of GSH in cells of H. polymorpha slightly changed the sensitivity/tolerance to chromate, but increased the rate of reduction of Cr 6 + and reduced