Abstract
The toxicity to the cells and protoplasts of Saccharomyces cerevisiae of the sugar analogues modified at carbon 2 increases in the order 2โdeoxyโDโglucose (DG), 2โdeoxyโ2โfluoroโDโglucose (FG) and 2โdeoxyโ2โfluoroโDโmannose (FM). The fluorohexoses, similarly as DG, behave generally as analogues of both glucose and mannose, depending on the hexose used as a carbon source in the medium. Relative inhibitions of glucan and mannan synthesis in protoplasts were found to be dependent more on glucose and mannose used as the growth support than on the type of the sugar analogue. Certain degree of structural relationship of fluorohexoses to the corresponding natural hexoses was reflected in their effects on growth of intact cells. Growth on glucose was inhibited most effectively by FM, growth on mannose by FG. The data obtained support the view that the sugar analogues interfere mainly with the glucoseโmannose interconversion catalyzed by hexosephosphateisomerases. A comparison of the effects of fluorohexoses and DG on the synthesis of extracellular invertase and intracellular ฮฑโglucosidase and alkaline phosphatase in protoplasts pointed to the fact that all three sugar analogues tested also participate in metabolic control of enzyme synthesis.