ИСТИНА

NAD+-dependent formate dehydrogenase (EC 1.2.1.2., FDH) is found in a wide range of liv-ing organisms, from bacteria and yeast to plants and fungi. FDH plays a important role in the cell life maintainance. For example, in pathogens and plants FDH is stress enzyme, thus its expression rises at stress conditions. Many pathogenic microorganisms can form biofilms to survive in and to adapt themselves to different strict conditions. The expression level of FDH in Staphylococcus aureus (SauFDH), a wide-spread pathogenic bacterium, increases up to 20-fold, when the bacterium is in the form of a biofilm. Irreversible inhibition of this enzyme can be a way to combat such a pathogen. In absolute majority cases there is high homology between FDHs from different group (50-60% and higher). Inside the group amino acid sequence homology is 80-95% and only SauFDH is exclusion from this rule. Exami-nation of a significant number of amino acid sequences of different FDHs revealed, that this enzyme shows very poor homology with FDHs from other sources, even inside bacteria (less than 40%). Thus thorough study of this enzyme is of great scientific and practical interest. Our laboratory carries out systematic studies of formate dehydrogenases from different natu-ral sources, and now we are focused on the bacterial FDH from S. aureus (SauFDH). The gene, coding SauFDH was cloned and expressed in E. coli. We also carried out a major cultivation of the enzyme (yielding more than 500 mg per liter of cultivation media) and developed a high-efficient purification system. Analysis of the SauFDH properties showed both advantages and disadvantages of the en-zyme. On the one hand, it possesses high thermal stability in comparison with FDHs from other sources and an outstanding catalytic constant. On the other hand, values of Michaelis constants both for NAD+ and formate are high, compared to ones for FDHs from bacteria, yeast and plants. This study was supported by Russian Foundation for Basic Research (grants 14-04-32042-mol_a).