Tag Archives: Saccharomyces cerevisiae
Biological aspects of non-enzymatic glycosylation
L. М. Lozinska, H. М. Semchyshyn
Vassyl Stefanyk Precarpathian National University, Ivano-Frankivsk, Ukraine;
е-mail: semchyshyn@pu.if.ua
Non-enzymatic reactions commonly play an ambiguous role in living organism. It is well known that non-enzymatic glycosylation may lead to disruption of the structure and function of biomolecules, thus initiating the development and accompanying different diseases. On the other hand, under certain conditions the products of non-enzymatic glycosylation act as signaling molecules and play an important role in the immune response. Data concerning the influence of non-enzymatic glycosylation and carbonyl stress on living organisms are summarized in the work. The role of reactive carbonyl compounds and reducing carbohydrates in glycation of biomolecules, involvement of non-enzymatic glycosylation in carbonyl stress development and interplay between glycation and free radical processes in living organisms are summarized. The basic ways to prevent glycation and formation of reactive carbonyl compounds that induce carbonyl stress are highlighted. Special attention is paid to the role of the yeast Saccharomyces cerevisiae as a model system to study the glycation processes in vivo.
Sensing and signaling for peroxisome autophagic degradation (pexophagy) in yeasts
A. A. Sibirny1,2
1Institute of Cell Biology, National Academy of Sciences of Ukraine, Lviv;
2University of Rzeszow, Poland
Yeast cells, similarly to cells of other eukaryotic organisms, possess intracellular organelles, including that of peroxisomes also known as microbodies. Enzymes of oxidative metabolism, mainly hydrogen peroxide generating oxidases, catalase, some enzymes of glyoxylic cycle and enzymes involved in catabolism of unusual carbon sources (n-alkanes, methanol) are located in peroxisomes. Especially important role is played by peroxisomes in methylotrophic yeasts, unique eukaryotic organisms capable to utilize one-carbon compound, methanol. Active proliferation and biogenesis of peroxisomes occur on methanol, so these organelles can occupy between 30 and 80% of cellular volume. After shift of methanol-grown cells into media with multicarbon substrates, such as glucose or ethanol, an excess of peroxisomes degrades in the specific process known as autophagic degradation of peroxisomes or pexophagy. There are 36 AuTophaGy related genes, known as ATG genes, which products are also involved in pexophagy. At the same time, not much is known on mechanisms of glucose and ethanol sensing and signaling which initiate pexophagy process. Proteins Pfk1 (α-subunit of phosphofructokinase), Slt2 (mitogen-activating protein kinase) Gpr1 and Gpa2 (components of GPCR system) and Snf3 and Ggt2 (high- and low-affinity glucose sensors) were found to be involved in signaling of glucose-induced pexophagy in Saccharomyces cerevisiae. In the methylotrophic yeast Pichia pastoris, glucose sensing protein Gss1 was found to be important for glucose-induced pexophagy. Very few is known on mechanisms of ethanol sensing and signaling during pexophagy which is an important problem for future studies.
Defects in antioxidant defence enhance glyoxal toxicity in the yeast Saccharomyces cerevisiae
H. М. Semchyshyn
Vassyl Stefanyk Precarpathian National University, Ivano-Frankivsk, Ukraine;
е-mail: semchyshyn@pu.if.ua
Glyoxal being either exogenous or endogenous compound belongs to reactive carbonyl species. In particular, its level increases under disturbance of the balance of glucose intracellular metabolism as well as of other reductive carbohydrates. Having two carbonyl reactive groups, glyoxal readily enters glycation reaction that results in carbonyl stress development. Investigations of different model systems demonstrate a strong relationship between carbonyl and oxidative stress. However, a possible role of antioxidant system in the organisms’ defence against carbonyl stress is poor understood. In addition, the influence of glyoxal on living organisms is less studied than the effect of such carbonyl reactive species as malonic aldehyde or methylglyoxal. To study a potential role of antioxidant system in organisms’ defence against carbonyl stress induced by glyoxal, the baker’s yeast Saccharomyces cerevisiae was used. It has been found that strains with different defects in the antioxidant defence were more sensitive to glyoxal as compared with parental wild strain. Therefore, the data obtained in the present study confirm the relationship between carbonyl and oxidative stress and reveal the important role of antioxidant system in baker’s yeast defence against carbonyl stress induced by glyoxal.
Defects in tor regulatory complexes retard aging and carbonyl/oxidative stress development in yeast Sассharomyces cerevisiae
B. V. Homza, R. A. Vasylkovska, H. М. Semchyshyn
Vassyl Stefanyk Precarpathian National University, Ivano-Frankivsk, Ukraine;
е-mail: semchyshyn@pu.if.ua
TOR signaling pathway first described in yeast S. сerevisiae is the highly conserved regulator of eukaryotic cell growth, aging and stress resistance. The effect of nitrogen sources, in particular amino acids, on the activity of TOR signaling pathway is well studied, however its relation to carbohydrates is poor understood. The aim of the present study is expanding of our understanding of potential role of TOR regulatory complexes in development of carbonyl/oxidative stress that can result from yeast cultivation on glucose and fructose. It has been shown that the level of α-dicarbonyl compounds and protein carbonyl groups increased with time of yeast cultivation and was higher in cells grown on fructose that demonstrated their accelerated aging and carbonyl/oxidative stress development as compared with cells grown on glucose. The strains defective in TOR proteins cultivated in the presence of glucose as well as fructose demonstrated lower markers of the stress and aging than parental strain. Thus these data confirmed the previous conclusion on fructose more potent ability to cause carbonyl/oxidative stress and accelerated aging in S. cerevisiae as compared with glucose. However, defects in TOR regulatory complexes retard aging and development of the stress in yeast independent on the type of carbohydrate in the cultivation medium.