Fructose metabolism via the pentose cycle in tumoral islet cells.
In tumoral islet cells (RINm5F line) the phosphorylation of D-fructose is catalyzed by hexokinase rather than fructokinase. Fructose 6-phosphate appears to be preferentially channelled into the pentose cycle, as suggested by a ratio of D-[1-14C]fructose/D-[U-14C]fructose oxidation close to 2.7, the failure to generate 14C-labelled lactate from D-[1-14C]fructose and a poor metabolic response to menadione. When the islet cells are exposed to both D-fructose and D-glucose, however, the metabolism of the former hexose is dramatically modified, fructose 6-phosphate being now formed at a lower rate and preferentially channelled into the glycolytic pathway. These findings illustrate the existence of regulatory steps in fructose catabolism located distally to its site of phosphorylation.
Sener
A
A
Laboratory of Experimental Medicine, Brussels Free University, Belgium.
Malaisse-Lagae
F
F
Malaisse
W J
WJ
D007516:Adenoma, Islet Cell / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D005632:Fructose / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology; D007340:Insulinoma / Q000378:metabolism*; D007700:Kinetics; D010084:Oxidation-Reduction; D010190:Pancreatic Neoplasms / Q000378:metabolism*; D010427:Pentose Phosphate Pathway / Q000187:drug effects
D005632:Fructose; D005947:Glucose