Prokopiv T. Interrelations in iron assimilation, oxidative stress and riboflavin oversynthesis in flavinogenic yeast Pichia guilliermondii

Object of the research: iron homeostasis in yeast cells and oxidative stress under conditions that modulated of riboflavin (RF) synthesis. The aim of the work: identification of interrelations in iron assimilation, oxidative stress and RF oversynthesis in flavinogenic yeast Pichia guilliermondii. Methods: microbiological, physical-chemical, biochemical, genetic, molecular-biological, statistical. This work presents characterization of genetic, biochemical and environmental factors controlling the iron status and riboflavin biosynthesis in the wild type strains and riboflavin overproducing mutants of the flavinogenic yeast Pichia guilliermondii. Mutants rib80, rib81 and hit1 over-accumulate iron in the cells and overproduce RF even under iron replete conditions. Genetic analysis of rib80, rib81 and hit1 mutants revealed that mutations hit1 interacted synergistically with rib80 and rib81 in the regulation of the riboflavin biosynthesis, but not of the assimilation of iron. The high affinity iron uptake system function in this yeast species. It was identificated two genes encoding putative ferrooxidases that characterized of difference level of expression under iron replete conditions. It was found that valid heme synthesis is required for proper regulation of the iron uptake but not of riboflavin biosynthesis. It was defected of labile iron in cell of RF overproducers. It was found that iron deficiency and mutations causing riboflavin overproduction evoked increased intracellular content of reactive oxygen species, protein carbonyl groups and lipid peroxidation and decreased activity of antioxidant defence enzymes (catalase and superoxide dismutase). Treatment by superoxide generating agents enhanced flavinoganic activity and increased cellular iron of wild type and mutant. Fields of application: biochemistry, biotechnology, microbiology, genetic, molecular biology.