With increasing number of immunocompromised patients as well as drug resistance in fungi, the risk of fatal fungal infections in humans increases as well. The action of echinocandins is based on the inhibition of β-(1,3)-d-glucan synthesis that builds the fungal cell wall. Caspofungin, micafungin, anidulafungin and rezafungin are semi-synthetic cyclic lipopeptides. Their specific chemical structure possess a potential to obtain novel derivatives with better pharmacological properties resulting in more effective treatment, especially in infections caused by Candida and Aspergillus species. In this review we summarise information about echinocandins with closer look on their chemical structure, mechanism of action, drug resistance and usage in clinical practice. We also introduce actual trends in modification of this antifungals as well as new methods of their administration, and additional use in viral and bacterial infections.

For over 70 years thiamine (vitamin B1) has aroused the interest of biologists, biochemists and medical doctors because of its multilateral participation in key biochemical and physiological processes. The thiamine molecule is composed of pyrimidine and thiazole rings which are linked by a methylene bridge. It is synthesized by microorganisms, fungi and plants, whereas animals and humans have to obtain it from food. There are several known forms of vitamin B1 inside cells: free thiamine, three phosphate esters (mono-, di-, and triphosphate), and the recently found adenosine thiamine triphosphate. Thiamine has a dual, coenzymatic and non-coenzymatic role. First of all, it is a precursor of thiamin diphosphate, which is a coenzyme for over 20 characterized enzymes which are involved in cell bioenergetic processes leading to the synthesis of ATP. Moreover, these enzymes take part in the biosynthesis of pentose (required for the synthesis of nucleotides), amino acids and other organic compounds of cell metabolism. On the other hand, recent discoveries show the non-coenzymatic role of thiamine derivatives in the process of regulation of gene expression (riboswitches in microorganisms and plants), the stress response, and perhaps so far unknown signal transduction pathways associated with adverse environmental conditions, or transduction of nerve signals with participation of thiamine triphosphate and adenosine thiamine triphosphate. From the clinical point of view thiamine deficiency is related to beri-beri, Parkinson disease, Alzheimer disease, Wernicke-Korsakoff syndrome and other pathologies of the nervous system, and it is successfully applied in medical practice. On the other hand, identifying new synthetic analogues of thiamine which could be used as cytostatics, herbicides or agents preventing deficiency of vitamin B1 is currently the major goal of the research. In this paper we present the current state of knowledge of thiamine and its derivatives, indicating the participation of these compounds in the regulation of cell metabolism at both the coenzymatic and non-coenzymatic level.

Oxythiamine is an antivitamin derivative of thiamine that after phosphorylation to oxythiamine pyro phos phate can bind to the active centres of thiamine-dependent enzymes. In the present study, the effect of oxythiamine on the viability of Saccharomyces cerevisiae and the activity of thiamine pyrophosphate dependent enzymes in yeast cells has been investigated. We observed a decrease in pyruvate decarboxylase specific activity on both a control and an oxythiamine medium after the first 6 h of culture. The cytosolic enzymes transketolase and pyruvate decarboxylase decreased their specific activity in the presence of oxythiamine but only during the beginning of the cultivation. However, after 12 h of cultivation, oxythiamine-treated cells showed higher specific activity of cytosolic enzymes. More over, it was established by SDS–PAGE that the high specific activity of pyruvate decarboxylase was followed by an increase in the amount of the enzyme protein. In contrast, the mitochondrial enzymes, pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase complexes, were inhibited by oxythiamine during the entire experiment. Our results suggest that the observed strong decrease in growth rate and viability of yeast on medium with oxythiamine may be due to stronger in hibition of mitochondrial pyruvate dehydrogenase than of cytosolic enzymes.Key words: pyruvate dehydrogenase, 2-oxoglutarate dehydrogenase, transketolase, pyruvate decarboxylase, activity, oxythiamine, inhibition.

Oxythiamine (OT) and 3-deazathiamine (DAT) are the antimetabolites of thiamine. The aim of study was to compare the effects of OT and DAT pyrophosphates (-PP) on the kinetics of mammalian pyruvate dehydrogenase complex (PDHC) and the in vitro culture of HeLa cells. The kinetic study showed that 3-deazathiamine pyrophosphate (DATPP) was a much stronger competitive inhibitor (K_i = 0.0026 μM) of PDHC than OTPP (K_i = 0.025 μM). Both K_i values were much lower versus K _m for thiamine pyrophosphate (0.06 μM). However, DATPP added to the culture medium for the HeLa cells culture did not hamper the rate of cell growth and showed not significant impact on the viability of the cells, whereas OTPP and OT showed a significant cytostatic effect. The differences between the thiamine antivitamins in their effect on cell growth in vitro may be due to differences in physicochemical properties and difficulty in DAT transport across the cell membrane.

Candida albicans and Malassezia pachydermatis cause human and animal infections of the skin and internal organs. We compare the properties of two enzymes, pyruvate decarboxylase (PDC) and malate dehydrogenase (MDH), from these species and from Saccharomyces cerevisiae cultivated under aerobic and anaerobic conditions to find differences between the enzymes that adapt pathogens for virulence and help us in searching for new antifungal agents. Malassezia pachydermatis did not show any growth under anaerobic conditions, as opposed to C. albicans and S. cerevisiae. Under aerobic conditions, C. albicans showed the highest growth rate. Malassezia pachydermatis, contrary to the others, did not show any PDC activity, simultaneously showing the highest MDH activity under aerobic conditions and a K_mvalue for oxaloacetate lower than S. cerevisiae. Candida albicans and S. cerevisiae showed a strong decrease in MDH activity under anaerobic conditions. Candida albicans shows four different isoforms of MDH, while M. pachydermatis and S. cerevisiae are characterized by two and three isoforms. Candida albicans shows about a twofold lower activity of PDC but, simultaneously, almost a threefold lower K_mvalue for pyruvate in comparison with S. cerevisiae. The PDC apoform share under aerobic conditions in C. albicans was 47%, while in S. cerevisiae was only 26%; under anaerobic conditions, the PDC apoform decreased to 12% and 8%, respectively. The properties of enzymes from C. albicans show its high metabolic flexibility (contrary to M. pachydermatis) and cause easy switching between fermentative and oxidative metabolism. This feature allows C. albicans to cause both surface and deep infections. We take into consideration the use of thiamin antimetabolites as antifungal factors that can affect both oxidative and fermentative metabolism.