Presence of fructokinase in pancreatic islets.
Homogenates of rat pancreatic islets that had been heated for 5 min at 70 degrees C to inactive hexokinases, catalyzed the ATP-dependent phosphorylation of D-fructose. This reaction was dependent on the presence of K+ and was inhibited by D-tagatose although not by D-glucose or D-glucose 6-phosphate. The phosphorylation product was identified as fructose 1-phosphate through its conversion to a bisphosphate ester by Clostridium difficile fructose 1-phosphate kinase. These findings allowed the conclusion that fructokinase (ketohexokinase) was responsible for this process. Similar results were observed with tumoral insulin-producing cells (RINm5F line). Fructokinase may account for a large share of fructose phosphorylation in intact islets, particularly in the presence of D-glucose.
Malaisse
W J
WJ
Laboratory of Experimental Medicine, Brussels Free University, Belgium.
Malaisse-Lagae
F
F
Davies
D R
DR
Van Schaftingen
E
E
D000818:Animals; D004795:Enzyme Stability; D005631:Fructokinases / Q000302:isolation & purification*; D006358:Hot Temperature; D007328:Insulin / Q000096:biosynthesis; D007515:Islets of Langerhans / Q000201:enzymology* / Q000378:metabolism; D010766:Phosphorylation; D010770:Phosphotransferases / Q000302:isolation & purification*; D051381:Rats
D007328:Insulin; D010770:Phosphotransferases; D005631:Fructokinases; C046173:fructokinase