Effect of thiamin on the content of fructose 2,6-bisphosphate in Euglena

Abstract 1. 1. Thiamin deprived Euglena cells contained twice as high a concentration of Fru-2,6-P 2 in sufficient cells and the rate of the uptake of glucose from the medium was twice as great as that found in sufficient cells, indicating that Fru-2,6-P 2 is responsible for the glycolysis. 2. 2. Moreover, incubation of thiamin deprived cells with increasing thiamin concentrations caused a decrease of Fru-2,6-P 2 . The activity of Fru-6-P, 2-kinase was affected by thiamin and the activity of PFK-2 in thiamin deprived cells was 2.3 times greater than that observed in sufficient cells. 3. 3. Incubating thiamin-deficient cells in a thiamin-containing medium, the activity of Fru-6-P, 2-kinase decreased rapidly and became the same activity as that found in thiamin sufficient cells. 4. 4. In contrast, the two thiamin dependent 2-OGDC and PNOR activities showed a reverse relationship, being higher in thiamin-sufficient cells and lower in thiamin deficient cells. 5. 5. We concluded that the carbohydrate metabolism of Euglena is regulated by Fru-2,6-P 2 through an intracellular concentration of thiamin based on the present evidence.