Fructose metabolism in the human erythrocyte. Phosphorylation to fructose 3-phosphate.
In human erythrocytes, the first step in the metabolism of fructose is generally thought to be phosphorylation to fructose 6-phosphate catalysed by hexokinase. In variance with this assumption, we show here that fructose in these cells is metabolized primarily to fructose 3-phosphate by a specific 3-phosphokinase. This process has an overall estimated Km of 30 mM with respect to extracellular fructose and an apparent Vmax. of 0.6 mumol/h per ml. At a fixed concentration of fructose in the medium, the accumulation of fructose 3-phosphate was linearly dependent on the duration of incubation up to 5 h and was not affected by glucose. Once accumulated, fructose 3-phosphate appears to be degraded and/or relatively slowly metabolized, decreasing by only approximately 30% after a 12 h incubation in a fructose-free medium.
Petersen
A
A
Department of Clinical Biochemistry, State University Hospital (Rigshospitalet), Copenhagen, Denmark.
Kappler
F
F
Szwergold
B S
BS
Brown
T R
TR
D004912:Erythrocytes / Q000378:metabolism*; D005632:Fructose / Q000378:metabolism*; D005636:Fructosephosphates / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D010766:Phosphorylation
D005636:Fructosephosphates; C062519:fructose 3-phosphate; D005632:Fructose