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Undifferentiated suspension culture cells had the ability to transfer glucose and fructose actively, but the suspension culture cells were unable to transfer saccharide without previously splitting to monosaccharides. The uptake of fructose showed the low- and high-affinity system compared to of glucose, which possessed only one saturable uptake system. In this paper, the low affinity system of the uptake of fructose has been studied intensively. Glucose did not inhibit the low affinity system of fructose competitively. The Km value was 47 mM for fructose, 7.4 mM for glucose and Vmax was 69 μmol/h.g fresh weight for fructose, 9.8 μmol/h.g fresh weight for glucose. Metabolizer inhibitors, both 50 μM of CCCP and DNP, inhibited 70% of the uptake of the low affinity system of fructose. The proton ions were accompanied by the uptake of fructose. The stoichiometry showed ratio of proton to fructose was 0.17. The mechanism of the uptake was fructose-proton-symport. The molecules of fructose accumulated inside 25 times more than outsde. Therefore, the low affinity system of fructose was not mere diffusion, but depended on metabolic energy and thus transported actively. The importance of this system was discussed.
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